Can CBC ciphertext be decrypted if the key is known, but the IV not?

Question: Let's say that there is a binary file encrypted with AES in CBC mode (i.e. using a key and initialization vector). If key is known, but IV is not, is it easy to fully decrypt the file?
How hard is it?
Comment: Welcome to Cryptography Stack Exchange. I changed the title and tags a bit, as your question (and the answer) actually applies to all block ciphers when used with CBC, not only AES.
Comment: Yes, starting from the last block back to the first. I'm going to write a demonstration below.
Comment: Dang, I looked over and over for a dupe.
Answer: With CBC (Cipher block chaining) mode, before encryption, each block is XOR-ed with the ciphertext of the previous block, to randomize the input to the block cipher (and avoid encrypting the same block twice with the same key, as this would give the same output, and tell the attacker something about the plaintext).
As the first block has no previous block, here the initialization vector will be used instead.
On decryption, we will apply the block cipher to each ciphertext block, and then XOR the result with the previous ciphertext block (or the initialization vector, for the first block).
As all ciphertext blocks are known, and we have the key, we can reliably decrypt everything other than the first block, even if no or a wrong initialization vector is given.
For the first block, we actually have no information at all, without the initialization vector, other than that it has the same length as any other block (16 bytes for AES): Every 16-bytes plaintext can be reached by supplying the fitting IV. Fortunately (or unfortunately, depending of your point of view), in many file formats the first some bytes are fixed (or almost fixed, or can be guessed based on the rest of the file).
So, with CBC-mode, a secret initialization vector gives almost no protection, if the key is known to the attacker.
This applies generally: Protocols rely on the key being secret, while an initialization vector can usually be public, and often is even transmitted together with the ciphertext.
In CTR mode, a secret initialization vector (there called "nonce") will actually help a bit more to keep the plaintext secret - but if the attacker can guess even one plaintext block (and has the corresponding ciphertext block), he can (given the key) calculate the corresponding counter value, and from this the nonce. Don't let the attacker have the key.
Answer: Yes, you can, but you might not be able to decrypt the first block if you don't know the IV.
CBC encryption encrypts block-by-block, using the previous ciphertext XOR'ed with the current plaintext block as input of the block cipher, the result of which form the ciphertext blocks.

So you can decrypt each block by performing the block decrypt, and then XOR-ing with the previous ciphertext block, giving you a plaintext block.

This can be performed for each block, with the possible exception of the first block, for which you need the IV. If you don't know you can try and guess the IV. If the result of the decryption already looks like plaintext then the IV is probably all zeros.
If you cannot find out any information about the IV then you're out of luck for the first block of plaintext. The reason for this is that the IV then acts as the key stream of a one-time-pad. And a one-time-pad is fully secure in a information-theoretical sense.
AES always has a block size of 16 bytes, which means that the first 16 bytes of the encrypted message might remain secret.

Note that it is quite common to prefix the IV to the ciphertext. If you cannot read the initial 16 bytes (assuming AES) then it might well be that the first 16 bytes are the IV and that the plaintext starts at the second block.

Images by WhiteTimberwolf (SVG version)
Answer: Paŭlo Ebermann's answer is spot-on.  For a working example using openssl, consider the ciphertext below, which was encrypted using AES-128-CBC.  The encryption key used was 1AFFB43263983EE5C3DC75BC5FF76D06, but the iv is not known:
7ea9fac5d627a27f7c3ec776cc059bd0
8219a48d3a9b6e0ed263d2d54f7953c8
025ca84b88574ce567af96482598a496
0e76394cbe347fd5ddbca644272979cb
6ee3287d3ccc02520bfdd53c93c4de5b
b85488940d97f8295139c445defefb73

The output above is formatted with 16 bytes in each row, so that each row of 16 bytes represents one block of ciphertext.  Without the iv, we can not decrypt the first block, but we can decrypt all of the remaining blocks.  To do so, we simply remove the first block of ciphertext, and use this block as the iv:
echo -n '8219a48d3a9b6e0ed263d2d54f7953c8025ca84b88574ce567af96482598a4960e76394cbe347fd5ddbca644272979cb6ee3287d3ccc02520bfdd53c93c4de5bb85488940d97f8295139c445defefb73' | xxd -p -r | openssl aes-128-cbc -d -K 1AFFB43263983EE5C3DC75BC5FF76D06 -iv 7ea9fac5d627a27f7c3ec776cc059bd0

The resulting plaintext is:
even years ago our fathers brought forth on this continent, a new nation…

Can you guess what the first block of plaintext was?
Answer: Despite the IV is usually public in real world, let me assume the only IV you don't know is the first because the IV used for each other block is the corresponding previous block:
C2 = Encryption (K, C1⊕P2) ⇒ P2 = C1 ⊕ Decryption (K, C2)
The expression above can be used to compute all the subsequent blocks; the first is computed as follows:
C1 = Encryption (K, IV⊕P1) ⇒ P1 = IV ⊕ Decryption (K, C1)
For the first block I can get the value of IV⊕P1 from Decryption (K, C1) as I know K and C1.
Comment: Don't forget to remember the Kerckhoffs's principle: A cryptosystem should be secure even if everything about the system, except the key, is public knowledge.


Technical term for this kind of image

Question: Vinyl cutters often reduce photos to pure black and pure white for rendering in one color of vinyl against another color background. Popular tools for this are apps like Adobe Capture, the threshold command in Photoshop, etc. This is often referred to as "stencil" style, but that seems inadequate because these images are not usually valid stencils because of trapped white space. "Vectorized" also seems inadequate because that can also refer to multi-color images. I am wondering what the technical term for this type of processed image would be.
Comment: "Crappy one-color image trace of a color photograph" :)
Comment: "Woodcut" comes to mind, although that typically would have sharper edges.
Answer: While vectorized, woodcut and posterizing are also accurate descriptions, I believe the technical term for this is a two tone silhouette.
There are many free tutorials online if you search this term and, of course, there's always the Image Trace function in Illustrator if you're looking for a quick fix.
Answer: Based on a quick google search using the terms "posterizing black and white image," I was returned with a number of links nearly identical to the images you've provided.
Curiously, the top return was an SE page:
How to create an artistically posterized monotone portrait?
I recognized the posterized aspect of the image and added the black and white aspect to restrict the results. Some of the results appear in greyscale, but that's a minor consideration.

Technical term for this kind of image


Can you text a business/sole trader promotional material if they put their number online?

Question: eg. An electrician has put their mobile number on a website to attract business. Can I legally contact that electrician to tell them about a product that he/she may be interested in? .. Everything is based in the united kingdom.
Comment: What makes you think that the number you see can receive text messages? Many businesses operate from land lines, not cell phones. What country are you asking about?
Comment: Hi Ron, The United Kingdom.
Answer: No.
From here:

Organisations must not send marketing texts to individuals without
  their specific, valid and prior explicit consent. This consent must be
  recorded and kept as proof of consent. There is a limited exception
  for previous customers, which is known as the soft opt-in. A soft-opt
  in only applies if the organisation have obtained the contact details
  in the course of a sale (or negotiations for a sales) of a product or
  service to the customer; they are only marketing their own similar
  products or services; and they gave the customer an opportunity to
  opt-out of the marketing, both when first collecting the details and
  in every message thereafter.
Comment: Thanks Greendrake, could it not be argued that putting your number online for people to contact you is consent.
Comment: @jon Nope, because they put it online to be contacted regarding _specific_ purpose. This does not constitute consent to be contacted just about anything.
Comment: thanks.. I hear you.. though it seems very unfair that businesses setting up today can't reach out to potential customers with targeted messages, without having to pay huge advertising costs to companies that all got away with spamming back in the day. I mean how can you get a potential customer give you permission to contact them without you first contacting them?
Comment: @jon Do you like spam? Or do you think your proposal is any different from spam? Certainly there will be a chance that some of your recipients are glad you contacted them, but the vast majority will be annoyed. Do you think it is fair to annoy 95% of people to get 5% satisfied? Then, market is about the balance of supply and demand, not about fairness. You either afford lawful advertising, or you are out.
Comment: true, but I would say there is a marked difference between someone that sends 1000 one time messages to people that may well have a legitimate interest in the message than someone that sends out multiple messages to a million random people.. I would consider the first to be legit marketing and the second spam. As I understand it, this used to be case.
Comment: @jon Although I might welcome a targeted advertisement through some means, text message isn't one of them.  If you are legitimately selling a service you think the recipient will like to only those who will be interested, you can afford to take the trouble to do it right (perhaps in the mail).  If it's not worth it to you to do more than send out texts, you're spamming.
Comment: Hi David, I agree that advertising a business requires more than sending out some texts.. but I wanted to find out the legality of sending texts. It appears that legally the only way to contact a potential customer 'unsolicited' is by cold calling them. I know I'd rather receive a text than a phone call... I think the law should be expanded to differentiate between direct marketing and spamming.


Valve (most likely) hitting crank case: complete engine replacement?

Question: 2011 Subaru Impreza has been sounding "cranky" for a while; last week, it finally escalated to the point where it sounded like someone was under the hood, banging on the engine with a crow bar.. Fast forward to today, where the shop says "something went wrong inside the crankcase," on the invoice and specifically told me they think it's the valve hitting the crank case and the engine will need to be completely replaced. Are there no other options, nothing else that can be done? Car only has 42,734 miles on it - a complete replacement seems extreme.
Answer: Well, the valve can't hit the crankcase directly. The valve can hit the piston directly. Then the piston can get damaged and then parts can fall into the crankcase. No matter the terminology, if there is damage done to the piston and there are parts in the crankcase or laying in the oil pan. Then I would say replacement is necessary. If it was just a bent valve and a piston that is damaged just on top/combustion chamber side, then I would say rebuilding would be possible. However, the man-hours and the parts costs of rebuilding if not doing it yourself would be higher than just replacing it.
I would have them show the damage to you or someone you know, that is good with these matters. Have them boreoscope the spark plug hole and or have the damage exposed with the pan off. See what you and the person you trust thinks, then go from there.


My car stereo does not save radio station presets

Question: I have a 2005 Honda Accord with original radio. The problem is that it doesn't save any radio station presets. Well, sometimes it does, it seems like when the engine is hot and I program the stations then it saves them, but never overnight or longer periods when the engine is switched off. And it's only the radio station presets that will go, the other settings are fine.
Comment: I'd guess that it is not getting electricity when the car is turned off.
Answer: I would say that as it is saving the other settings that it is getting a constant live from the battery.
And assuming that no on has messed around with the wiring all SHOULD be well. However it's clearly not so i would guess that this is an internal issue and only reoslution would be a replacement unit.
However, in some cases where the wiring has been 'altered' then both the constant live and ignition/accessory live are wired together to the ignition/accessory live meaning that once the ignition is tunred off, then all settings are lost.
I hope this helps but i can't think of any other reason, other than an internal fault that would cause this.


Is VMWare Fusion bought through the MacUpdate Spring 2012 Bundle a full valid version?

Question: I'm considering buying VMWare Fusion 4. On vmware.com it's available for $49.99. MacUpdate is currently also offering a bundle which includes VMWare Fusion and 10 other apps, for a total price of $49.99 (MacUpdate Spring 2012 Bundle). I'm not particularly interested in any of the 10 other apps, but they might be nice to have. I'm wondering if there's a catch to this offer though. For example, I seem to remember that a similar bundle offered in the past didn't include the right to discounts when upgrading to future versions. So is buying VMWare Fusion through this bundle fully equivalent to buying it through VMWare.com?
Answer: In addition to the answer of Diago, I got this from the MacUpdate FAQ :

What's the catch?
There isn't one! You get the exact same versions of the apps as if you
  paid full price! The same support, update, and upgrade options are
  available to you, as well.

So, yes! Buying the spring bundle will give you a full valid version!
Comment: +1 For a more official answer. I was just looking for this on the site but my searching skills failed me today.
Answer: Yes
Bundled software, specifically those sold by MacLegion and MacUpdate are 100% fully licensed versions of the applications. I bought Parallels 6 this way last year, and recently upgraded to 7 using the upgrade price without any issues.
MacLegion and MacUpdate sell 4 bundles a year, and they spend a significant amount of time negotiating the deals with the companies that offer the bundles. Since they have build such a good reputation, they tend to come up with some very legit and good deals.
Unless explicitly specified these are full licenses with no string attached. I have bought around 75% of the software I run this way, and one of the reasons I love owning a Mac.
These specials are Cyber Monday coming early.
I can confirm that outside of MacLegion and MacUpdate, I have bought bundles where this is not the case, however, those were small, not as well known bundle suppliers, and the software clearly stated that they don't qualify for updates.
Comment: @WheatWilliams I am not sure how I am not answering that. Yes you would. It's a fully valid license, and every piece of software I have bought in this method I have upgraded, including Parallels as I mentioned.


Who produced the sound?

Question: In Exodus 19:13 (NASB)

(...) When the ram's horn sounds a long blast, they shall come up to the mountain."

Who produced the trumpet sound?
Comment: Joshua was to sound the ram's horn. - Both Joshua & Moses ascended the mountain in Exodus 24:13. Moses descends with two heavy stone tablets, leaving Joshua to gather Israel with a shofar sound to hear God's commandments.
Answer: It seems to be a miraculous event among other miraculous events.

Exodus 19:10 And the Lord said to Moses, "Go to the people and consecrate them today and tomorrow. Have them wash their clothes 11and be ready by the third day, because on that day the Lord will come down on Mount Sinai in the sight of all the people.

It is an extraordinary day.

12 Put limits for the people around the mountain and tell them, 'Be careful that you do not approach the mountain or touch the foot of it. Whoever touches the mountain is to be put to death. 13They are to be stoned or shot with arrows; not a hand is to be laid on them. No person or animal shall be permitted to live.' Only when the ram's horn sounds a long blast may they approach the mountain."

No actor is mentioned. No words from God or Moses is mentioned. The timing seems like a miraculous signal from God.

14 After Moses had gone down the mountain to the people, he consecrated them, and they washed their clothes. 15Then he said to the people, "Prepare yourselves for the third day. Abstain from sexual relations."

They are ready for a sequence of miracles.

16 On the morning of the third day there was thunder and lightning, with a thick cloud over the mountain, and a very loud trumpet blast. Everyone in the camp trembled. 17Then Moses led the people out of the camp to meet with God, and they stood at the foot of the mountain. 18Mount Sinai was covered with smoke, because the Lord descended on it in fire. The smoke billowed up from it like smoke from a furnace, and the whole mountain  trembled violently. 19As the sound of the trumpet grew louder and louder, Moses spoke and the voice of God answered him.

The mountain miraculously trembled violently as the sound of the trumpet grew miraculously louder and louder.
Who produces the sound?
God or perhaps his appointed angels. It was a crazy day of a supernatural show when God descended on Mount Sinai.
Answer: At the establishment of the Israelite covenant at Mt Sinai in Ex 19-23, we have a series of clear divine miracles including:

V16 - thunder and lightning
V16 - a thick black cloud
V16 - (see also V13) - a long blast of the ram's horn (a trained musician can do this for perhaps 1 minute - but this obviously last much longer confirming the divine origin)
V18 - the mountain enveloped in smoke
V18 - the LORD descended in fire
V18 - mountain quaked violently
V19 - sound of the ram's horn continues and gets louder and louder

These series of spectacular supernatural events made a deep impression on the people because they constantly referred to them later such as Ex 24:17, Deut 4:11, 15, 5:4, 5, 22, 23, 9:10, 15, 10:4, Heb 12:18.  (See also Rev 8:8, 10, 12, 9:1, 14).  Other Scripture also discusses a loud trumpet blast from God, see Matt 24:31, 1 Cor 15:52, 1 Thess 4:16.
I see no reason to suggest that the very extended sound of the ram's horn that grew louder and louder was anything other than part of the supernatural display of God's glory to impress the people with the importance of what was about to occur - the giving of the covenant and law.

Who produced the sound?


In Bayesian network graphs, how to systematically search for conditional independent nodes?

Question: In Bayesian network graphs, how to systematically search for pairs of conditional independent nodes, and the associated condition node(s)? Is there some simple rules or algorithms to follow?
Answer: Yes, you can find conditionally independent nodes by evaluating the graphical structure of the Bayesian network. Check out the notion of D-separability which provides 3 rules:
1) X -> Y -> Z
2) X <- Y -> Z
For both (1) and (2), Z is conditionally independent of X given Y
3) X -> Y <- Z
X and Z are marginally independent, however, given Y (or any descendant of Y), they become conditionally dependent!
Andrew Moore has some explanation of these rules on his website.
Answer: There is the Bayes-Ball Algorithm, described in this paper: http://www.gatsby.ucl.ac.uk/~zoubin/course05/BayesBall.pdf
On page 22 of these slides there is a handy diagram that summarizes the algorithm:
http://ai.stanford.edu/~paskin/gm-short-course/lec2.pdf


Everything Was Fine Then Brushes stopped affecting mesh

Question: I was sculpting my first ever object in blender. It was working fine no issues, then i switched between object & edit modes and came back to sculpt mode when applied my brushes those did not affected my mesh. I checked all settings again if everything is correct like Dyntopo, Start and end clipping, symmetry, Brush stroke, Brush Radius everything was selected and enabled. I surfed through internet for to find out people facing same issue to solve my problem. but could not.
Maybe, i am still wrong at something. If you guys check my file and see through that would be the most help for me today.
Answer: You've masked the whole surface, you can't sculpt on the masked surface, press AltM to unmask.
Comment: Thank you, it helped! It is so dumb of me applying mask and then forgetting.
Answer: I don't do sculpting, so can't help much...
But here's a video where it explains how to configure the hot keys of each of your brushes so they work correctly:
https://youtu.be/eGuDCgU_4os
And this is an old video that solves some common problems of sculpting:
https://youtu.be/DAdYQ4xpNo0
If nothing of the above helps, then save your project file, and try uninstalling and reinstalling blender again, or use a portable (zip) version of blender... Then open your file and check if the brushes are working again
Comment: Hi. Link-only answers are discouraged, if the link goes down so
does the answer. Please help us making this site a real
knowledgebase and add all relevant steps to your answer. Thanks.


Is Typeface and Type Family the same thing?

Question: I'm currently taking a graphic design course on Coursera, and the instructor uses these words interchangeably. Therefore, does Typeface and Type Family mean the same thing?
Comment: I'd say that "type family" is the broader term as it may contain several type *faces*. When asked for a recommendation for, say, a cover design, I can either suggest a very specific font ("Berthold Akzidenz Bold")  or be more general  ("try Berthold Akzidenz"). One is a face and the other a family.
Answer: Often slight differences between terms are missed when starting out. Some terms are mis-used, and some are misunderstood.
I like to use an analogy or a metaphor to help distinguish between similar terms. If I'm lucky, the analogy holds and the answer helps make things clearer
Type designers will sometimes make different weights (stroke thicknesses), style variations, and set (width) of a basic design for different uses.
For example: Some publications prefer to set body text in a serif face, heads and sub-heads with sans-serif, and italics for emphasis. That's three different typeface styles. That's three different typefaces.
If they share common design characteristics, they are said to be in the same type "family" as the specified plain face. The document has a coherent and harmonious organized appearance.
As in real life, some families are bigger with more family members than others. They tend to be more versatile and can be used in demanding situations such as reference works and fine typography.
We often use a word to express a whole family. "Smith" and "Times" are two examples of popular family names. To labour the analogy, Mr. Smith is a "Smith" family member and Times italics is a "Times" family member.
They're close; but, they're not the same, and not quite interchangeable.
Answer: A typeface is one specific style of lettering: Times, Helvetica, Poetica, Adobe Garamond.
Sometimes there is just one typeface to that name, period: Michelangelo, Caliban, Harrington.
Since in most programs you have the ability to add formatting to a typeface (like bold or italic), and in layout progams you want aesthetic flexibility, type designers have created different styles (formatting) and different weights (thicknesses) of many typefaces.
So instead of highlighting a word and clicking the Italic button (which may tell the program to just skew all the letters), you select the Italic style (which substitutes an entirely different font file, properly designed to look italic).
Helvetica has weights from 25 (ultra thin) to 95 (ultra heavy), plus italic versions, plus condensed versions, plus expanded versions. All those faces together are called the type family.
Answer: Are "typeface" and "type family" the same thing?
Yes, they are the same.
The only difference is how you look at it.
"Type family" stresses the existence of different styles and weights as well as sizes. For example when you think of the "Times family", you would probably think of italic and bold as well as roman.
"Typeface" doesn't particularly stress those kinds of variation. For example if you are considering different sizes of Times type your context may be one in which you are only discussing roman, or you might as well be, and therefore variation in style and weight isn't relevant. Therefore in this context you may prefer to refer to the "Times typeface".
But it is fully accurate to say both that Times 14pt roman and Times 14pt bold are "instances of the Times typeface" and that Times 14pt roman and Times 6pt roman are "members of the Times type family".
Comment: It's also just as accurate to say that they are typefaces in the Times type family.
Comment: Times 14pt roman is a font, not a typeface.
Comment: Sorry, I read right through the size specification in the post – I read it as just 'Times roman'. Times 14pt roman, etc., is only a font in the traditional sense, of course; in the digital age, TimesRegular.ttf (or whatever the file name is) is a font belonging to the Times type family.


How to make musical phrases on guitar

Question: I have played classical guitar for many years, but my training has been all about playing pieces, and no improvisation was included; everything just technical, and I am in a very good state in it. Recently I have started to play electric guitar and am trying to learn to improvise. Man it has been a tough path! I have learned pentatonic scales, the patterns, have learned many of the basic chords, and I have grasped the fundamentals of scales over chord progressions, but when I play a chord progression and start to play with it, I can only play very simple and boring stuff. I can't make any nice phrases. What do I lack? What should I learn next? Thanks.
Comment: It sounds like you're ultimately struggling just with the concept of composition.  Learning to improvise is basically learning to compose on the fly.  Do you have any experience with composition?
Comment: Yes, several times, but again very classical, writing some motifs, variations, and adding harmony/counterpoint. It seems at least very different from what people like Eric Clapton do. Or David Gilmour, Or Jimmy Page, many others. Although Gilmour is different with Page or Clapton in many aspects, they all seem similar when compared for example with J.S.Bach. To me the way a musician from baroque, classical or romantic periods saw the process of composition, was different from all the people after jazz. I think I understand those previous ones, but not these modern ones!
Comment: What kind of music do you want to make?
Comment: I guess it can be summarized in Rock! But I love blues too.
Answer: If you haven't already, I would start by learning the 7 modes on guitar. Ionian, dorian, etc. They can be found here.
This is where I started and I'm by no means an expert at improvising, but once I further understood when to use which mode when soloing over certain keys it definitely helped my ability to improvise on the spot.
This next part is going to require a basic understanding of music theory. Modes can be kind of confusing at first, because in any given key (for example C), all the modes play the same notes but just start and end on different notes. Ie D Dorian would be played D,E,F,G,A,B,C,D. The usefulness of this is best shown when soloing/improvising over certain chords. For example, if you are improvising over a C chord and you're playing C Ionian (which is just C Major) you're going to notice certain notes sound weak, certain notes sound strong and certain notes a little tense. This is because of the notes within the C chord clashing with the soloed notes. Ie the E in the C chord does not play nice with F when soloing, and D may sound tense. Practicing this will show you much more than me telling you. However, if you're playing over a G chord, and you're playing G mixolydian, different notes are going to feel tense, strong or weak. Now the F that we were playing over C Ionian that sounded kind of weak, sounds great when playing over a G chord. The quality of the notes change as you change the chord you're improvising over.
In an attempt to summarize that paragraph, modes will help you understand the relationship between the notes you're soloing and the chords you're playing over.
Another tip that may help:
I've always found that I always want to go back to my "default" solo scales and riffs. Forcing yourself to break out of this by using a different scale, mode, etc or changing the timing I found helped with improvisation.
Comment: Not sure if that's a typo or a misunderstanding but the Dorian scale that you showed would actually be called D Dorian, which consists of all of the same notes as C Ionian/Major.  The next reference to this is when you refer to C Mixolydian, where I believe you would want to say G Mixolydian, which consists of all of the same notes as C Ionian/Major.
Comment: @JeremyW Thank you very muh for your detailed answer. I think you showed me a very good next step. I would probably mark this as answer, but I will wait a little bit more to get more answers! Thanks again!
Comment: Yes, C Dorian is actually the Dorian of Bb. The mode you mean is called D Dorian, with the notes from the C maj. scale. Confusing, but important. Imagine discussing what to play with another player - the two involve different keys and won't work well together.
Comment: @Basstickler  Yes agreed. Definitely a mis understanding that I never knew I had. Thanks. I'll edit the question.
Answer: I would suggest copying solos or even just phrases from those people that you admire. Each musical genre is its own language. Even if you know the grammar you still need to practice speaking the phrases. Then you can start to deviate from the learned solo or phrases or embellish it or mix and match phrases from different influences.
Also you can try learning different patterns in a scale. Instead of up and down the pattern try up all the way in thirds or fourths or fifths etc. You could even incorporate classical music phrases into improve with a more modern.
Try learning a pattern to really quick chord changes to challenge your theory technique and then try jamming for 20 minutes on a one chord vamp to challenge your melodic sense.

How to make musical phrases on guitar


Question didn't bump

Question: I edited this answer and posted this answer but they didn't bump.
Comment: Is it possible that you are viewing some other tab, and not active? When I look at questions tagged ([tag:extension-field]) and choose [the tab displaying recently active questions](http://math.stackexchange.com/questions/tagged/extension-field?sort=active), I see it at the top.
Comment: Thanks! I also see it at the top when I click on your link, but I don't see it if I go to http://math.stackexchange.com and choose the "interesting" option among the options "interesting", "featured", "hot", "week", "month". I just wonder why. PS: here is the link: http://math.stackexchange.com/?tab=interesting
Answer: After the clarification in the comments it seems that it is not a bug - whether you see recently active questions depends on the way you view the site.

If you go to https://math.stackexchange.com/questions then you have several tabs to choose from. If you want to see the question which have some recent activity, you have to choose the active tab.
IIRC active tab used to be also here: https://math.stackexchange.com/. However this was changed not so long ago. See here for more details: Question update notice not showing any more and Proposal: make the "interesting" tab the default on Math.SE homepage.

Question didn't bump


Want tag for graphviz

Question: It would be great if there were a tag for questions about graphviz within jupyter notebooks.  This would be applicable to the question How to display graph with MathJax in jupyter notebook?.
Answer: Before I start, I need to say that the referenced question, is a really great question.  I hope it gets some good answers.
And as to the inquiry about adding a new tag, thanks for bringing it to Meta.  But...
Let's ask ourselves why do we tag?  If you follow that link, you will find (to my mind) that there are two primary benefits to tags.

For me, the most important point of tagging is to help me find questions to answer.
The second most important reason for tagging (in my opinion) is to help others find the information they may need.

I would argue that the referenced question, while a great question, is narrow enough, that tagging it as specifically as suggested, is unlikely to help it find an answer-er, or help those needing the answer find the answer via the tag.  And thus, the suggested tag is not likely to be super beneficial.

Want tag for graphviz


Convolutional neural network & recurrent neural network vs. dense feedforward networks

Question: What are the benefits of convolutional neural networks structures and recurrent neural network structures compared to the dense feedforward network when there would be enough computing power to represent any arbitrary function?
Answer: This is an interesting question, let be just rephrase it a bit differently:

Fully connected (FC) Neural Networks are known to be unifersal function approximators (i.e. they can approximate any function). If we had infinite computation power, would there be any reason to use Convolutional Neural Networks (CNNs) or Recurrent Neural Networks (RNNs)?

Even if we had enough "computing power" and we weren't at all interested in efficiency (i.e. solving the same task quicker with less parameters), there is still the issue that Fully Connected Neural Networks tend to overfit very easily. Actually I answered a similar question the other day on why "CNNs are less prone to overfitting than FC networks". Besides that CNNs have some useful properties relating to images, the most notable is translation invariance (i.e. the network is invariant to translations in the image). This is very useful in image classification where the object that we want to classify can be anywhere in the image.
A similar case can be made for RNNs: Because they can exploit the sequential nature of the data, they can solve problems that wouldn't be possible with FC networks. Through the context of its previous states it can extract information and enhance its performance. This gives it the ability to identify trends and seasonalities in the data, which are impossible to identify in a FC network. Even if we had an arbitrarily-large FC network and we passed it the full sequence in every time step (so that it doesn't miss out on any of the context), that would mean that the RNN requires less information (i.e. fewer features) about that given time step (because they can obtain this information from another time step). This makes less dimensions for the data so less room to overfit.
As a rule of the thumb the more parameters in a model, the more data required to train it without overfitting!
So, generally speaking, if we can get the same work done with fewer parameters, it is advantageous (faster and more efficient computation, less memory required, less prone to overfitting).
Answer: CNNs are very sparse compared to dense networks, meaning that there are fewer parameters to estimate. In addition to this being nice for computing times, it reduces the potential to overfit to training data. CNNs don't just drop parameters the way that you can specify in Keras with a dropout command. CNNs are smart about which parameters are forced to be zero, exploiting structure present in the data. Which parameters get dropped by a dropout command in Keras will depend on the particular training data. CNNs will drop the same parameters every time. Further, CNNs force some connections to share parameters, again by being smart and exploiting structure present in the data. Together, these reduce the variability of parameter estimates (some can't vary from 0) to combat overfitting.
Remember that performance on training data isn't interesting. It's all about the ability to generalize to unseen data.
If you've never drawn out what a couple of 2x2 filters do to a 3x3 image, I suggest drawing out what happens. CNNs are typically thought of in terms of putting squares on top of bigger squares. However, they're absolutely neural networks with predictable numbers of parameters and nodes. As an exercise, if you have two 2x2 filters and a 3x3 image, how many nodes are in the next layer, and how many parameters are there? You can check your answer in Keras.


After episode 3 of season 8, how many dragons do the allies have?

Question: In the E03 S08 of Game of Thrones, the two living dragons, respectively ridden by Deanerys and Jon, fight against the dead dragon, ridden by the Night King.
During the fight, Jon's dragon happens to fall down to the ground. When I watched the episode, I supposed the dragon was dead.
At the end of the episode, a dead dragon come into Winterfell to breathe blue fire everywhere. Is it the first dead dragon the Night king was riding, or is it Jon's dragon, killed during the dragons fight, who came back to life after the Night King summoned all the dead on the battlefield ?
And finally, how many dragons do we have left ?
Answer: It's the first dead dragon the Night king was riding, because his neck is perforated. And during the fight we saw Jon's dragon hurt the other one.


What does 'clock rate' mean in the context of recurrent neural networks (RNNs)?

Question: I have often encountered the term 'clock rate' when reading literature on recurrent neural networks (RNNs). For example, see this paper. However, I cannot find any explanations for what this means. What does 'clock rate' mean in this context?
Answer: It seems this paper defines a "clock period ${T}_n$" that it uses to express the topology of the network: "Each module is internally fully-interconnected, but the recurrent connections from module j to module i exists only if the period $T_i$ is smaller than period $T_j$.".
This definition is, however, only in this paper, as far as I know. It wouldn't make sense to have a "clock period" (or "clock rate") on other, more self-similar, RNNs. However "time t" is something that is defined to express the amount of times the RNN has recursed, "t times".
Comment: Thanks for the answer. So what exactly does "clock rate" mean in the context of the linked paper?
Comment: @ThePointer "clock rate" refers on how modules process data. The idea of the paper is to compute information at different "rates", for this, it uses modules, the modules are connected to others according to the module's clock period.  This creates a network where information is processed by each module at different rates. Quote: "Each module $i$ is evaluated only every $T_i$-th time step", this would be a 'rate' of computation of incoming data.
Answer: The purpose of a clockwork RNN is to help with long term dependencies. Let's say in this case, we have a sentence that starts with "John went to..." and at no point again is John's name mentioned throughout the few paragraphs we are passing to our model.
As mentioned in the paper, the most common method to combat this (at the time) was using an LSTM that stored long term data in it's cell state, or as put in the paper:

[an LSTM] uses a specialized architecture that allows information to be stored in a linear unit called a constant error carousel (CEC) indefinitely

However, this requires a whole heap of extra parameters in order to work (input gate, output gate and forget gate which all require parameters). So proposed was the CW-RNN.
The fundamental idea behind a clockwork RNN is to have "modules" computed periodically. First to clear things up, a timestep is 1 input into the model. So in the case of our example, if we're inputting character by character, timestep 1 is the character "J", timestep 2 is "h" and so on; "o", "n", " ", "w"...
So what is the clock-rate? Well, it's simply how often each module of the CW-RNN is computed. Let's say the hidden layer of the clockwork RNN is split into 8 modules, which I will reference as $M_1, M_2, M_3 ... M_8$, and the associated clock-rates for each of these modules are the powers of 2, so: $1, 2, 4, 8, 16, 32, 64$ and $128$.
Before I continue I want to note a potential discrepancy, if you consider the first input to be timestep 0, then it changes how this executed (all modules would be activated at the first timestep), however if you consider it to be 1 (like I do for this example), only module 1 would be executed (again, in this example).
So we're at timestep 1, ie "J", so we check the timestep against the clock-rates of each module to determine which ones will be executed in the computation of the hidden state and output for this timestep. To do this, we take the mod of the timestep against the time-rate, so: 1 mod 1, 1 mod 2, 1 mod 4 ... 1 mod 128 and if it equals 0 (basically, is the timestep a multiple of the time-rate) then that module will be executed at this timestep. So in this case $M_1$ will be executed. When we input "h" at timestep 2, $M_1$ and $M_2$ will both be executed, and will equally contribute to the hidden state (ie, they will be added together) and the output.
By performing calculations this way, each module can all simultaneously be responsible for information over different time periods, for example $M_8$ which is only executed every 128 timesteps will be responsible for very long term dependencies, but $M_1$ will cover short term dependencies.
So in basic terms, clock-rate refers to how often (what timestep interval) a given module of a Clockwork RNN is computed
Comment: According to the paper, yes it does "CW-RNNs beat both RNN and LSTM networks by a considerable margin of 8-20% on average" for classification and " CW-RNNs give by far the best results, with the
smallest one being roughly on par with the second-biggest
LSTM network" for sequence generation
Comment: Thanks for the answer. So does a CW-RNN actually produce superior results to the LSTM (for this purpose of 'long term memory')?


1 ltr Milk is not curdling even after squeezing 2 lemons; What could possibly wrong?

Question: I was trying to make Paneer (a type of cheese). So I boiled once then added 2 table spoons of lemon juice. Milk should be separated out instantly from water but it's been 20 minutes.. And milk is still unchanged.
Comment: It isn't very clear what are you trying to ask? You asked 'Is that milk good for health'? Do you want to consume the unseparated milk and concerned about its safety? or are you asking 'Why didn't the milk curdle' and how to rescue it?
Comment: what kind of milk is it? UHT pasturised milk doesn't curdle very well.
Comment: have you tried warming up the milk again?
Answer: Milk proteins will coagulate at particular temperatures and Phs. You wrote that you used 2 Tbs of lemon juice but you didn't say how much milk you added that to. If you used too much milk then the mixture will not be acidic enough. Follow a recipe.
You also wrote that you boiled the milk once. I don't know if it is a language barrier issue but it sounds like you boiled the milk in the past. The milk needs to be at near boiling temperatures when you add the acid. The combination of heat and acid will cause the milk proteins to unravel (denature) and tangle up with each other (coagulate) which will result in the curd you are looking for.
If the milk has been handled well, that is if you didn't leave it out overnight, then it has likely not spoiled and you can try again by either adding more acid or bringing to a boil as necessary.
Comment: Good point @EssKay (I asked the OP to clarify as well) but we also get 2 lemons in one place and 2 tbsp juice in another
Comment: The title says 1 ltr of milk.
Comment: @EssKay- Thanks. My brain very helpfully filtered out that information when I was rereading the question.
Comment: looked closely that it isn't just a superfine flakes? agitation can do that
Answer: Have you checked if the milk is ultrapasteurized? Ultrapasteurization denatures the curds of the milk, allowing it to briefly withstand room temperatures in transport. However, it makes it so curdling (and by extension, cheese) is impossible.
Comment: This does not provide an answer to the question. Once you have sufficient reputation you will be able to comment on any post; instead, [provide answers that don't require clarification from the asker](https://meta.stackexchange.com/questions/214173/why-do-i-need-50-reputation-to-comment-what-can-i-do-instead).
Answer: I'm making paneer for the first time, too, and I was having a hard time getting it to curdle and googled why, and ended up here.
There is some question about the milk/acid ratio you are using. I was using Indian recipes, and none of them provided a precise ratio. Look up how to make cheese. All cheese making starts this way and regular cheese recipes have more precise measurements to start with. It's not exact and never will be, suffice to say, a measurement is just a starting point and knowing you might have to gradually add more acid is all the instruction you can hope to get.
Here's what I've learned so far:

Don't boil the milk.
Heat milk slowly enough so that it doesn't scald.
It needs to get to at least 180°F/82°C
It's okay to stir the milk while it's heating up to help prevent scalding.

Tips: Before you add the acid, stir the milk so that the milk is moving when you add the acid. Don't stir the milk after you add the acid. Turn off the heat and wait up to 15 minutes for the curdle. It doesn't happen immediately. Different types of milk will take more or less time to curdle, but the curdling opportunity is complete at 15 minutes. If the curdle isn't complete, don't stir, and heat the milk again. The curdle may complete while heating, this instruction is as imprecise as the amount of acid. My tip is to take care to heat it correctly the first time!
The milkiness of the water is cheese! The water (whey) should be clear-ish. It might be yellow-ish. Look at several YouTube videos on cheese making to see what clear-ish looks like. I say several because some are less clear than others.
Lastly, I suggest experimenting with smaller amounts of milk until you get a decent result. And try to remember that different types of milk behave differently. Different acids behave differently.
It's not complicated, but that isn't the same as easy.
The next thing you'll be fighting is the softness of the cheese. Lots of recipes use the word "soft" to talk about the texture, what they mean is, not rubbery. Not rubbery is what soft cheese is!
I had to laugh at all the times I accidentally curdled milk, and there I was trying to curdle it, and it wouldn't!
I was able to make a decent batch of paneer, and you will too.
Answer: May be it is UHT milk or it is low-fat milk. In US, the milk that we get in normal grocery shops don't curd well for paneer. You can use the milk from Whole Foods.
Answer: The milk could be adulterated, treated with detergent, urea, or made using milk powder.
Milk instantly curdles to form cottage cheese when lemon juice or vinegar is added.
Adulteration is rampant in India. Even if it's just diluted with water it should curdle to some extent; even skimmed milk curdles, although it would produce less cottage cheese. The separated water is whey.
If you're in the US, maybe it could be added corn syrup that could hinder curdling of milk?
Answer: I would imagine that either it's very diluted milk, or would try checking out what happens if the milk were a little hot/warm. That usually speeds up curdling. Otherwise, the milk should be fine, I don't see any reason for it to become unfit for consumption.
Answer: Simply, you might be using aluminium or some reactive metal pot. I made the same mistake, use steel or iron.
Comment: The oxide layer on an aluminum pot will not react with citric acid enough to prevent curdling.
Answer: 1L UHT MILK + 1 Tbsp LIME JUICE = CHEESE CURDS
seriously, to everyone who only have uht milk, don't bother with the lemon and vinegar, etc. it doesn't work, i just tried it. i squeezed 1 whole lemon + 1 Tbsp vinegar to 1 liter uht milk and nothing was happening. i was about toss the whole thing out but thought to try lime juice. just 1 Tbsp lime juice and it instantly curdled. DONE.
Comment: What worked for you was 1 lemon, 1 tbsp, vinegar, and 1 tbsp lime juice. That's not surprising: All else being equal, milk curdles once the acidity reaches a particular level. But you shouldn't assume that the citric acid in limes is different from the citric acid in lemons. Adding more lemon juice would presumably *also* have worked.


Is it possible our new tire fitting has had something do with leaking coolant?

Question: We just got front passenger tire replaced on jeep Cherokee and now car is losing coolant like crazy. We have looked under the hood & looks like the damage is in this same area. There was no leak prior but was hoping someone could plse give an idea of likelihood that this can occur (fitting / putting on hoist etc). The guys that fitted the tires are good blokes & have done stuff for us before however it seems a bit of a coincidence to have happened directly after & any knowledge to go in & talk to them about would be much appreciated as on bones of butt & cant afford to fix something they have damaged, if they have.  Thanks for your help & pic for reference :)
Comment: Are you certain that's coolant?  That seems to be an odd color for a Jeep.  Check power steering and ATF first.
Comment: IMHO whether the car was on a ramp or on a jack - neither will have affected your cooling system. This is likely to be coincidence.
Comment: Thanks for replying! :) is hard to see in the pic & my explanation is terrible but it looks from what we can see that the pipe has been hit / broken which has caused the leak & was wondering if when they jacked it up it either wasn't sitting "just right" or they could have accidentally smashed it.
Comment: Welcome to Motor Vehicle Maintenance & Repair!
Comment: @SteveRacer new jeeps use hybrid oat fluid which is red/orange/pink. The ps fluid is clear, for an electric pump i forget exactly, mineral oil maybe. It could be atf but the staining in the first few pics suggests coolant.
Comment: I sit correctificated.
Answer: While it is really hard to tell from the pictures, I'd suggest your analysis could be spot on. If the mechanic who fitted the front tire jacked the vehicle up from the area where the leak is occurring, I can see where a coolant leak would ensue. It appears from the pictures, the area where your are pointing to the leak is at the bottom of the radiator or possibly the core support. If they jacked it up from there, it certainly could have cause a crack in the cooling system, which would then dump coolant. Now, we don't know if that's what they did, but I'm suggesting it is possible that it could happen. You may want to tread carefully with the shop and not go in guns blazing, but rather, ask a manager the same way you asked here if this is at all possible.


Allow horizontal resizing from only one side of a shape

Question: Visio shapes have 8 resize handles. If I protect the height of the shape, only the handles in the middle of the left and right borders remain active. Now, is there a way to disable the left resize handle so that only the right one remains active?
Answer: The answer to that is no, although it would be a nice feature.  If you want to expand a shape in a particular direction, you might be able to change it local pin position via the Size and Position window (View / Show / Task panes / Size and Position).  IE, if you set the Pin Pos to Center Left, then dragging the right handle would expand the shape to the right.  The default pin position is generally in the center of the shape.


My Email Security is Low

Question: I use Gmail to exchange confidential and important documents with my customers. The documents are read by an unauthorized person (during sending the email) that I don't know him/her. How can I solve the problem?
Comment: Note that if your documents are definitely being intercepted (I can;t tell from your wording if they are or you suspect they are or you worry they might be)  then you are facing a targeted attack, which is very serious, and you should get expert help.
Answer: E-mail is not designed to protect the confidentiality of the information sent, hence additional security mechanisms are needed.
To ensure that only the specific recipient will be able to access the information sent, you could use public-key cryptography. A free and open-source implementation is GNU Privacy Guard (GPG).
GPG (and similar implementations) is able to preserve:

the confidentiality of information by encrypting it;
the integrity of information by signing it.

To get started, take a look at this GPG Cheat Sheet. I'd also suggest using specific add-ons, like Enigmail, that make it way easier to manage and use GPG.
It's important to notice that your customers must generate their own pair of keys (public and private), otherwise you won't be able to encrypt information to be shared only with them.
If this is not possible, you may have to rely on different (and less ideal) ways. A possible solution is to provide your customers with an FTP directory, where the data will be placed, and to share the password via other channels (e.g. SMS). Another solution, but not as secure as the previous ones, is to encrypt a zip file containing the information and send the password to the customer via SMS or any other non-email channel.
Comment: You say that 'E-mail is not designed to protect the confidentiality of the information sent, hence additional security mechanisms are needed.'. I have a question. As far as I know, Gmail uses SSL; So, Why do you say this?
Comment: SSL in this instance is one of the additional security mechanisms that Gurzo mentions - it is something Google have added on top of standard email to improve security. Importantly, it is not enough, because it can only protect the mail as it travels between you and Google - it does't protect the mail as it travels between Google and your client.
Comment: @Gurzo, Why GPG instead of DKIM/SPF?
Answer: You can use GPG or S/MIME to encrypt the contents of the email before sending it to your customers.

My Email Security is Low


Where's Keyboard Options in Loki?

Question: In Freya System Settings under Keyboard there used to be the Options tab with lots of options for configuring 3rd level key, ctrl key position, Alt/Win behavior etc...
Where can I access these options in Loki?
Comment: I'm curious to know what use case do you have for those options, which ones were you looking for? maybe there is a better alternative to do what you are trying to do.
Comment: Basically I need this options to make the keyboard behave the same way as a Mac keyboard. Having the control key position right next to space on the left hand side of the keyboard is much more comfortable for me to use shortcuts since I can use my thumb to press control and can maintain all other fingers at their base position. Thus pressing control Q in order to quit an application is just like pressing Q regularly, but with the thumb holding the control key.
Comment: (With the windows style of key placements I would have to use the pinky finger to hold control, but this is exactly the finger I would use to press Q. Alternatively I could move my whole hand out of typing position just to use a shortcut with my thumb on control, so it feels very disruptive to me.)
Answer: From the AppCenter install Tweak Tools, open Tweak Tools and select Typing to access all these options.

Where's Keyboard Options in Loki?


My houseplant with no identification.

Question: I brought this plant without a tag or any identification. This plant was way much fuller at the top. And as you can see a lot of empty space is there now. I don't know how to take care of it; however, it is growing long as you can see. But I always wondered why the top just disappeared. It was so full that you couldn't even see the dirt. I water every Saturday and let it drain completely. I don't use any fertilizer. What am I doing wrong? I need some instructions but unable to find any because I don't know the name of it. Any feedback?
Answer: Well done for posting good pictures - at first glance, I thought it was Pothos, but it's not, it's a Hedera variety, probably H. helix of some sort; in the UK, we just call it ivy, but I think in USA its known as 'English Ivy' (though they certainly are not all English!).
It's got pretty overgrown, and probably the pot is chock full of roots by now. Turn it out of its pot to check - if its solid with roots, take a bread knife (or any sharp knife, but a breadknife is very effective) and cut the rootball in half,or alternatively, pull it apart with your fingers if you can. Now cut back all the long growths to about six inches, less if you're feeling particularly brave, just above a leaf node, clean the pot and replace one of the halves in it, surround with fresh potting soil,pressing it down gently round the roots till the pot's full, water in well, allowing excess water to drain away freely. Then put it back wherever it was before (indoors presumably) and over time, it will produce new, bushy growth. This procedure is best done in spring, but I'm not sure it can wait that long.
Dispose of the other half, or pot it up if you want another one. Ivy grows virtually anywhere, including in low light, and is tough as old boots, but it does tend to increase greatly at the root, so turning it out of its pot yearly to inspect how much it's spread is probably wise, and repeating the cutting in half as described above if necessary yearly or biennially. If its not rootbound, just cut back all the growths, and give it some houseplant fertilizer (see below).
You can make even more plants if you like - every year in May I wrench apart the rootball of any ivy that's still healthy after being used outdoors for winter planting in pots and tubs, potting up the resulting sections of root plus topgrowth separately to make 6 or 8 plants, and grow them on during summer for use in autumn planting again. And when I say I 'wrench' them apart, I mean that quite literally, so that's how tough they are.
As for care ongoing, you can certainly use some houseplant food (Baby Bio will be fine, if its available there) if you like, from spring through to midsummer - other than being possibly rootbound though, it doesn't look unhealthy, but if its hung up fairly high with no direct daylight above it, then it will tend to produce more growth outward and down rather than up top.
Comment: Im saying empty the pot by removing the rootball of the plant, wash the pot thoroughly. Cut the rootball in half, and put one half of the rootball back into the clean pot, and add enough new potting soil around that cut half to fill the pot. Cutting the topgrowth is a separate procedure which can be done before repotting or after, and I don't mean you should bury some of the topgrowth in the pot.
Comment: Your absolutely right, roots are growing outside the pot. And daylight is not hitting it above it; apparently thats why the bottom has length. Great info. Thank you
Comment: Now when you say, 'clean the pot and replace one of the halves in it' what do you mean by that? Are you saying when I cut the long growth about 6 inches, to put half of that inside so it can start to grow up top to become full again?
Comment: Ok, I see what you're saying now

My houseplant with no identification.


Bone broth question

Question: Is it ok to partially cool chicken broth (prior to refrigerating ) with bones left in?  I left my chicken broth on a low simmer overnight, the next morning my husband turned the stock off to cool… He did not remove bones. Now I'm wondering if it is still safe to use (I removed bones and refrigerated stock within 2 hours)
Comment: Whether or not the bones are removed is irrelevant.  You might want to look at the related question on the right "I left stock out to cool overnight...", as it has information about cooling a stock.
Answer: Yes, in fact I would advise cooling the broth/stock a bit before putting it in the refrigerator. Adding hot foods to a refrigerator will drastically affect the foods inside. It takes too long to get from hot to cold and everything inside will be warmed up (to varying degrees) from the temperature fluctuation. Leaving the bones in, also not a problem. And it will make it easier to both skim the fat from the broth and remove the bones as the cooler temperatures will be easier to handle. Based on my experiences, everything sounds like you've handled it correctly.

Bone broth question


What is the "profile URL" field asking for when deleting an account?

Question: I am trying to delete my profile (from all of the stack exchange) and one of the fields in the "delete account" page is asking for a profile link or profile url. I have no idea what this is and no amount of searching this site has yielded any results, nor is it ever mentioned in the help center section on deleting an account. Either someone tell me what I need enter here or, better yet, one of you moderators make yourself useful and go do it for me. I WANT OUT!!! and if any of you hall monitors gets on here to tell me this is off topic or throw up some obligatory link to help page that doesn't help, so help me GOD i will hunt you down and write "dink" on your forehead in SHARPIE.
Comment: I'm sorry for the delay and the confusion. Your account is now scheduled for deletion.
Answer: It's the profile page, that you get to when you click on the section of the top bar with the avatar, reputation and badges. Yours is https://diy.stackexchange.com/users/23534/paperstreet and it should be automatically populated when you select "I need to delete my user profile" from the "contact us" page.
Since it's Friday night in North America as I write this, it might take a while for Stack Exchange staffers to process the form. After they do, there's a 24 hour grace period to allow for changes of heart (I believe there'll be a button on your profile page saying "cancel deletion" or similar).

I have to say, I'd be sorry to see you leave; you've provided some good information here, and I suspect you'd be a star on the upcoming woodworking site. If there's something about the site that the moderators can help resolve (understanding how the site works, conflicts with other users, whatever), please let us know, either in comments here or in chat (or a private chat session if there's something you'd prefer to discuss in confidence).
Comment: I've entered the exact link you provided in the profile url field and it pops up an error that says that's and invalid entry. I appreciate your comments on my past contributions here and I'd be willing to chat with you if you want to know what precipitated my decision to bail, but know that this isn't a cry for help, I'm done here as soon as I can close out my profile.


What are the rules for determining pregnancy?

Question: Suppose two characters have sex in-game. What are the rules for determining if a character is pregnant, how many kids there are (single birth, twins, triples, etc), and the gender(s) of the child(ren)?
Comment: Related question: [How to determine genetics in D&D](https://rpg.stackexchange.com/questions/40852/how-to-determine-pc-genetics-in-dd-for-the-purpose-of-creating-2nd-generation-p)
Answer: There are no mechanics in the core rulebooks regarding sex or pregnancy. This is something that would be entirely homebrew, or an RP mechanic between you and whatever you DM decides is appropriate.
Comment: Or how to generate descendants, for that matter.
Answer: You are looking for the Book of Erotic Fantasy.
Yes, many will tell you that D&D and sex should not mix, they are right. But we don't always do what's right, right? More often than not, someone will see another playing asking the GM "Are there whores in town?", leading to some quick randomization of fun events that will make (nearly) everybody at the table laugh.
While the topic certainly deserves some degree of caution, actually integrating it into a role-playing game is difficult to implement and tends to end badly if you are not prepared and open-minded about it.
Well, that 3rd party book has several sexual related rules for your games. You don't have to use all of them, or any of them. But some are interesting to read (or it was, back in early 2000s). It has several random tables to figure out things like the size of things, gender of things and how certain races will breed with others. It also has several topics that are interesting, like how to integrate sex into your games without it turning into a joke, how certain topics should be discussed with your players, and overall, it offers a mature view on the subject.
Just for the record, the book is not the worst rules splatbook released for 3.5 (and there are many in that category), and the flavor can certainly be adjusted to your tastes. Before the game was even released, it had drawn so much criticism due to the topics being discussed that Wizards revoked their d20 license and they had to publish it under the Open Gaming License instead.
Regardless of that, the book did open up a door for people to discuss sex in d&d, something normally and often frowned upon, like the excellent articles about Pregnancy and Consent from Kismet's Guide to Sex and Romance in Fantasy Gaming.
You will also find homebrew rules for pregnancy on dnd wiki, but those are nowhere near as interesting.
Comment: The weird semi-moralizing in the beginning of this answer is really off-putting. Also, while it's certainly true that *Book of Erotic Fantasy* has at least *some* useful material in it, and it's definitely not the *worst* supplement for 3.5e, this answer I think goes much too far in describing the book as a whole as useful. Much of it is immature and disappointing, and the mechanical content is wildly imbalanced.
Comment: You don't solely claim it's useful for the purpose of answering the question, though. The sections on pregnancy *are* fairly useful. Other sections, far less so—the prestige classes, for example, since they're liable to break your game. If you restricted your claim to merely answering this question, I'd have no objection to it. Though I would still object to the weird "this is bad, but we can be bad" introduction: it's *not* bad if the table's on board with it, which either makes it weirdly judgmental, or just self-contradictory.
Comment: I think this answer would be improved if it actually told us us the rules for determining pregnancy.  I understand that "the rules are in this book which has been out of print for years" is sort of an answer, but actually giving us the rules would be better.
Comment: @KRyan we will have to agree to disagree there. Maybe the book is not useful for the standard d&d game, but to the question at hand (*How to determine pregnancy*) it has enough rules to satisfy whoever is looking for those. I don't remember all the contents of the book by memory, and even if it sounds immature to one person, it may be useful to another that is looking exactly for that level of maturity on their game (even if by a joke).
Comment: @DanB Id have to resort to piracy for that, as I no longer own that book, which I would rather not. But to anyone who happens to have it, feel free to edit the answer. My objective here was merely to point out the existence of the (third party) book, as opposed to "there are no rules anywhere".
Answer: When Real Life meets DnD
Science time! (Note: I have encountered this as a DM myself)
So, IRL birth is a lot about law of probabilities. You have the female. Her egg will be in different positions (or not present at all) at different times of her cycle. Depending on fertility, she may or may not have produced more than one egg. These are both somewhat random factors determined by so many minor bodily functions that, overall, even modern medical professionals see it as at least partly chance.
Now the male. He will be...ahem..."giving" thousands or even millions of sperm cells in one mating. These cells, however, have to travel what, for their size, is a super-marathon. They don't have a guaranteed chance of actually encountering an egg. That's a bit of probability right there.
So, success of the mating in the first place should be a d100 Roll. As a DM, if the creatures are of the same race/breed and quite healthy, I generally say that any roll over 20 is success. If of a different race/breed or of "meh" health but logically still capable of mating I say that any roll over 40 is success. For really odd combos, unhealthy participants, or other factors that would logically affect it I will set it anywhere from 50 to 90. A totally impossible combination should just be forbidden from success. What constitutes each of these tiers is up to you.
Now, back to science.
Eggs produced determine the number of offspring. So this is also a die roll. Unless otherwise stated for this race in the flavor text ("XYZ mothers usually give birth to four offspring" or the like), as you are both characters assume the standard for humans and set the limit at triplets. Roll a d3 to determine the result.
Lastly, gender. This is a fairly simple d2 roll for each of the potential kids (assuming they had any).
The bigger issue
If these two lovebirds (or more illicit situations) are of the same race, you're good.
You don't make it clear, but generally we assume any humanoids with actual living bodies could mate. As a DM, you have to consider what you plan to do if they AREN'T of the same race.
Generally speaking, there are a few results:
1) Dominant bloodline. If really odd races are in play, you can rule that one bloodline is dominant genetically and entirely overrules the other, making the kids the race of that parent.
2) Unearthed Arcana Bloodlines. If one of the races/beings covered by the "Bloodlines" section in UA is in play, you could choose to use a base race and add a bloodline to it.
3) Hybrids. There are some hybrids listed in DnD -- Half-orc, Half-elf, etc. For races that don't have a hybrid, there is always the option of homebrewing one yourself from the two races involved (or creating something new from the combination, perhaps).
The Pregnancy Itself
Don't forget kids aren't born instantly. Make sure you account for the pregnancy of the mother. Usually 9 months long and progressing as it goes, this carries health factors, limitations, and dangers with it.
The mother, for example, should at some point experience random bouts of the nauseated state. Base land-speed should drop some, as well as carrying capacity. Certain types of damage (or over-exertion) should also come into play as potentially harming or killing the fetuses, resulting in a miscarriage.
Even the act of giving birth is something that should be handled carefully. Births are not always successes and often killed the mother and/or babies involved. That's something that you would need to address as a DM personally, however, because the medical/healing abilities available would determine the risk.
My own experiences here as a DM
I, in general, try to have my players at least avoid this. I would suggest explaining the potential impacts on them in game first so they realized the difference it makes.
That said, if you/they decide to go ahead, I've found it works well. I used in one aristocracy/feudal campaign for players that had family bloodlines and whatnot. The nice thing is that the pregnancy itself serves as a deterrent for future acts of the same kind. Creating new characters has a major plot impact, and is something you should seriously consider.
Out of humor I do tend to use this with Don Juan bard players...and usually results in a good bit of fun by the end of longer campaigns.
Generally, avoid true hybrids. These are drastically unpredictable when the events happen, and can result in totally broken offspring. I use the hybrid effect for rather simple beings usually, or ones that are very close together.
Also, don't be afraid to use DM Omnipotent miscarriages. More than once I have ensured an NPC did not give birth successfully because I knew it would negatively affect the plot.
Lastly, consider the impact of family. This can have cultural, social, and financial impacts on a character, and unless your campaign and players are ready to handle this I suggest against pregnancy entirely. Just DM rule that they are unsuccessful.
Comment: ...roll a *d3*? Triplets as likely as singleton babies? Why not use another percentage roll, and use actual data on human rates of multiple pregnancies? (Though to my understanding, various hormonal therapies available today can increase the chance of having more children, so modern data may be skewed somewhat upward.)
Comment: The line that "generally we assume any humanoids with actual living bodies could mate" is actually incorrect, if we're going by what *D&D* has generally done. In fact, earlier editions explicitly stated that hybrids were rare and almost all were half-human. We have gained greater variety of hybrids, but even to this day there are no official hybrid races for most of the core races (there are half-elf and half-orc, and *Dark Sun* has a half-dwarf in the mul, but those are literally the only hybrid combinations for core races). That is not a fair assumption to make.
Comment: Oh, and also, you have a typo (I assume) in the first line of the last section: "Don't forget kids *are* born instantly." I assume you meant *aren't* there.
Comment: Hi Alphaeus; please check [our guidelines for homebrew answers](https://rpg.meta.stackexchange.com/a/5154/1204). We request homebrew have a well-founded reason for being presented -- consider that a question asking for the rules for pregnancy *is not* answered by homebrew, unless that same answer demonstrates there are no rules already. We also want homebrew to be tested out in practice -- we *can* all just come up with something from our seats, but how well it works out in practice is the real differentiator. Can you include description of how this has worked out for you in actual play?
Comment: @KRyan With non-standard races, anything is possible, hence the d3 roll. As to the mating, I did not say with success. You can mate but not produce offspring, and I did state in my answer that the likelihood of success considered this factor. Fixed the typo, thanks for pointing it out, lol.
Comment: @doppelgreener I'll check those out. I guess I should add here the **as far as I and anyone I have spoken to before are aware, there are no defined rules regarding this, therefore needing homebrew** That said, I will include how it's worked for me.


Does  the Motorola Droid RAZR support NFC?

Question: Does Motorola RAZR XT910 support NFC with Gingerbread or Android ICS 4.0? Engadget says the device has an NFC controller. What does this really mean?
Answer: The RAZR does have an NFC chip in it. Currently the device does not have the drivers so the OS can make use of the chip. Motorola has been quoted to say that the RAZR is getting NFC support when the device gets the ICS update. Basically, the device could support NFC now, but Motorola, for one reason or another, did not include the components that would be needed for the Android OS to communicate with the NFC chip.

What are the benefits of upgrading a device to Ice Cream Sandwich?
Ice Cream Sandwich brings an entirely new look and feel to Android. It has a redesigned user interface with improved multi-tasking, notifications, Wi-Fi hotspot, NFC support and a full web browsing experience.
Comment: According to the Engadget link in the question above, the Linux driver is present but the hardware is misplaced/misconfigured. I believe that hardware is missing and the OS driver is present.
So, If I upgrade to Android 4.0 i will be able to use NFC right? Does XT910 & XT912 support NFC?
[Nexus vs Razr](http://www.computerworld.com/common/images/site/features/2011/10/galaxy-nexus-droid-razr-comparison-chart-2.jpg) says Razr support as NO.
I am very confused about this feature.
Thanks
Comment: if there was something wrong with the hardware, motorola would not be able to "turn on" NFC with just a software upgrade, which is what they are promising in the link. Your link says no, because the current version of the OS that motorola has on the RAZR does not have support for the NFC chip.
Answer: Yes it does have the controller. Now will it act like the nexus in NFC user friendliness? No. Required software is locked because what they are attempting to do is use a sim card as the antennae making Verizon able to control the NFC chips full capabilities. This way limits how much information can be transferred by NFC. Now it will be supported later on but if you truly want full blown NFC without restrictions then get the phones with supporting hardware.
Comment: Would you be so kind to add a source for this information, please?


Can I buy Bitcoins in Romania and if yes, where?

Question: I'm new here and I saw one can buy them e.g. in Germany at bitcoin.de via an online transaction, by paying Euros. Is the same possible in Romania (do you need a €-bank account for that?) and if so, is there some (online) exchange service best suited for that?
Answer: There are no exchanges yet that accept RON (Romanian Leu).
There are individuals in Romania who trade bitcoins for face-to-face cash trade:

https://localbitcoins.com/country/RO <-- But be careful of the listings who are not local, wanting to trade online instead.

Also there is the #Bitcoin-otc marketplace and the #bitcoin-otc-eu IRC channel in which you might find someone willing to trade.
If you have access to purchase UKash vouchers with cash, there are several services such as Mercabit.eu, VirWoX, and Bitcoin Nordic who will accept that voucher for the purchase of Bitcoins.
Otherwise, if you have the ability to send a SEPA transfer, there are many exchanges you can use, include BITSTAMP:

http://en.bitcoin.it/wiki/Buying_bitcoins
Answer: You can check out a list of exchanges that accept customers from Romania over here: https://bitcoinnews.ro/cumpara-bitcoin
If I remember correctly there's one international exchange that accepts RON as well and that's LakeBTC. I haven't seen any reviews of it though so use with caution.
Answer: I found a website that is selling directly, you can check it out under https://bitcoinx.ro/
Answer: See if bitstamp or kraken work for you. Both accept SEPA transfers. There are also some other European exchanges listed here.


conditional search

Question: I am looking for help with a conditional search based on four categories/taxonomies; countries/regions/type/no of bedrooms. What I am after is a dropdown search function that when I select a specific country, only regions in that country would appear in the region dropdown and in the type drop down, only types available in that particular region would be listed. I am obviously prepared to pay a fee for customisation.
JOHN
Answer: solution 1:

this can be done by adding the drop down menu to the search form.eg cat_slct
create a search template if its not exist in your theme.
add an if statement at the top of the page and directly after get_header();

-
if(isset($_POST['cat_slct'])){

    //make the query using the name of the categoty you'v just received via $_POST[].
    //or search within the database if necessary using the $wpdb object,it helps a lot.
}

}else{

    //the search page as its without modifying.
    //just you have to add the closing else tag before the get_footer();

}//right before the get_footer()

solution 2:

same as solution 1 but this time you'll create a page template and call it custom_search.
now go ahead and create a page that uses the custom_page template..eg name it search_cats.
tha different here is that you'll set the action of your targeted search forms to this page.
same as before: get the posted data and insert it into the query then do the regular loop.

conditional search


Standard deviation of Morlet wavelet's Fourier transform

Question: MATLAB has the complex Morlet Wavelet in the following form:
$$\psi(t) = \frac{1}{\sqrt{\pi f_b}}e^{\frac{-t^2}{f_b}}e^{j2\pi f_ct}$$
I arrived at its Fourier transform as shown below (another arrived at the same: Fourier Transform of Morlet wavelet Function?).
$$X(f)=\mathcal F(x)(f)=e^{-\pi^2 f_b(f-f_c)^2}$$
I sought a relationship between $f_b$ and the standard deviation of the Gaussian form of $X(f)$. Is it right? Is there any citable published literature (book or journal article) arriving at this relationship?
Rearranging this into the familiar Gaussian form,
$$X(f) = e^{\frac{-(f-f_c)^2}{2\left({\frac{1}{\pi\sqrt{2f_b} })}\right)^2}}$$
The standard deviation $(\sigma_f)$ of this frequency domain Gaussian is then,
$$\sigma_f = \frac{1}{\pi\sqrt{2f_b}}$$
Rearranging it,
$$f_b = \frac{1}{2{(\pi\sigma_f)}^2}$$
Answer: I might have the ingredients to an answer here and here and here.


insert data from a asp.net form to a sql database with foreign key constraints

Question: i have two tables
asset    employee
assetid-pk    empid-pk
empid-fk
now, i have a form to populate the asset table but it cant because of the foreign key constraint..
what to do?
thx
Tk
Comment: May we have the Insert statement in a generic format?
Answer: Foreign keys are created for a good reason - to prevent orphan rows at a minimum. Create the corresponding parent and then use the appropriate value as the foreign key value on the child table.
Answer: You should think about this update as a series of SQL statements, not just one statement.  You'll process the statements in order of dependency, see example.
Asset
  PK AssetID
     AssetName
  FK EmployeeID
  etc...

Employee
  PK EmployeeID
     EmployeeName
  etc...

If you want to "add" a new asset, you'll first need to know which employee it will be assigned to.  If it will be assigned to a new employee, you'll need to add them first.
Here is an example of adding a asset named 'BOOK' for a new employee named 'Zach'.
DECLARE @EmployeeFK AS INT;

INSERT (EmployeeName) VALUES ('Zach') INTO EMPLOYEE;
SELECT @EmployeeFK = @@IDENTITY;
INSERT (AssetName, EmployeeID) VALUES ('BOOK',@EmployeeFK) INTO ASSET;

The important thing to notice above, is that we grab the new identity (aka: EmployeeID) assigned to 'Zach', so we can use it when we add the new asset.
Answer: If I understand you correctly, are you trying to build the data graph locally before persisting to the data?  That is, create the parent and child records within the application and persist it all at once?
There are a couple approaches to this.  One approach people take is to use GUIDs as the unique identifiers for the data.  That way you don't need to get the next ID from the database, you can just create the graph locally and persist the whole thing.  There's been a debate on this approach between software and database for a long time, because while it makes a lot of sense in many ways (hit the database less often, maintain relationships before persisting, uniquely identify data across systems) it turns out to be a significant resource hit on the database.
Another approach is to use an ORM that will handle the persistence mapping for you.  Something like NHibernate, for example.  You would create your parent object and the child objects would just be properties on that.  They wouldn't have any concept of foreign keys and IDs and such, they'd just be objects in code related by being set as properties on each other (such as a "blog post" object with a generic collection of "comment" objects, etc.).  This graph would be handed off to the ORM which would use its knowledge of the mapping between the objects and the persistence to send it off to the database in the correct order, perhaps giving back the same object but with ID numbers populated.
Or is this not what you're asking?  It's a little unclear, to be honest.


My nokia lumia 635 wont detect my ear buds

Question: I am using a pair of skull candy earbuds and the phone dosent register that there are ear buds plugged in. But the weird thing is that i plugged in a pair of my friends earbuds and they worked. and then i plugged my earbuds into his phone and the ear buds worked. what could i do to make them work on my phone. Oh and i have restarted my phone and turned it on and off again.
Answer: May be there is a mismatch between size of jack... Sometimes it just gives the music... No audio... I am sure u would have tried rotating the hands-free.. If you haven't then try it.


How can you detect an insecure, non-random token?

Question: I know that some of PHP's random functions are insecure due to them not being completely random and are considered a bad practice. My question is how an attacker go about finding that the developer used an insecure function to create a token, such as a forgotten password token or CSRF token?
Answer: You can't actually determine how random a number is, because it's the nature of randomness. However, if you had a series of values, you could perform statistical randomness tests on the values and possibly find patterns/weaknesses in the random number generator. Certain patterns may give away what random generator was used. But even supposing the numbers were random in a statistical sense, the problem that remains afterwards is security. Something that passes randomness tests may not actually be secure!
In short:

true randomness = security
statistical randomness ≠ true randomness
Comment: A naïve way to detect randomness is to create 256 counters corresponding to the 256 possible values of a byte and then count the bytes (the more, the better). At the end of the count, you should have similar values for all of the counters with a little bit of deviation from `total_bytes_counted / 256`.

http://en.wikipedia.org/wiki/Diehard_tests has more interesting ones, some which are easy to make a quick and dirty implementation of in PHP for testing.
Comment: I had a bit of fun slacking at work today. I made a dice with paper, scotch tape, and a sharpie, rolled it 100 times, and then compared it with the numbers that https://www.random.org/dice/ gave me. Random.org's numbers are *really* random, so it's something good to test against. I put the data in here: http://www.php-developer.org/ttest.php.

Generate some values and play around with it. There are a lot more tests you can do in Microsoft Excel or LibreOffice Calc: http://depts.alverno.edu/nsmt/stats.htm

Cheers!
Comment: Thank you. I appreciate the reply. If something is statistically random, are there any easy ways to detect it? Or would it simply be analyzing them on your own and looking for patterns?
Comment: Thank you. I have another question and I don't know if I should bring it to chat or not (but I didn't see a chat dedicated to security), but what would be a good proof of concept for a company to prove that their tokens have a low degree of randomness? Being able to actually predict the outcome would be nice, but I don't see a way, or an easy to way to do that.
Comment: http://stats.stackexchange.com/questions/30/testing-random-variate-generation-algorithms seems to approve of the Die Hard tests for you very scenario as well.
Answer: Further to Kevin Li's answer, testing your session IDs for randomness is covered here: How to test session identifier strength with OWASP WebScarab
You need to request loads of session tokens and perform a statistical analysis on them to determine if they appear to exhibit the desired level of randomness. 10^4 session IDs would be a good minimal starting point IMHO but it would be best to analyse more if you can.
There is also an automated tool in PortSwigger's Burp proxy to do the same thing which I use but burp is quite expensive.
(would comment on the other answer but I don't have the rep)
Comment: Appreciate it. I actually have Burp and will try that


Missing 'Input format'

Question: On my inherited Drupal 6 site when I go to edit or add a news story 'Input format' is available for the Teaser, but not for the Body. I would like it for both or if it can only for one, have it on the Body so that I can choose an option such as 'Full HTML' so that images display. How do I achieve this?
Comment: Have you checked the settings on the body field?
Comment: How do I do that?
Answer: check your CKeditor settings in the following path:
yoursitename/admin/settings/ckeditor/editg
If you find anything related to this
"your content type@node/add/your content type.edit-body" in the "Fields to exclude/include: " textarea, just remove.

Missing 'Input format'


Why did Snow not destroy the Victors' Village in District 12?

Question: When Katniss Everdeen visits what is left of District 12, we see loads of dead bodies (well, what's left of them) and the destruction of the entire place. We then see that Victors' Village is pretty much untouched. What was the reasoning for this?
Comment: Note: I changed tag just to keep it consistent with previous two installments (in case you were wondering).
Comment: It's definitely an idea. I tend to let the mods of Napoleon take care of synonyms!
Comment: @AndrewMartin ... there should possibly be synonym tags for this, but agree with you. Was wondering that when I created the other tag.
Answer: Whilst answers from the movie are always good, the Mockingjay novel discusses this in its very first Chapter. It states:

Almost nothing remains of District 12. A month ago, the Capitol's
  firebombs obliterated the poor coal miners' houses in the Seam, the
  shops in the town, even the Justice Building. The only area that
  escaped incineration was the Victor's Village. I don't know why
  exactly. Perhaps so anyone forced to come here on Capitol business
  would have somewhere decent to stay. The odd reporter. A committee
  assessing the condition of the coal mines. A squad of Peacekeepers
  checking for returning refugees.

At the end of the first chapter, Katniss discovers a fresh white rose among dried, dead flowers on her dresser. She realises immediately that Snow has sent it. Quoting again from the book:

When I begin to gag at the stench, I back away and clear out. How long
  has it been here? A day? An hour? The rebels did a security sweep of
  the Victor's Village before I was cleared to come here, checking for
  explosives, bugs, anything unusual. But perhaps the rose didn't
  seem noteworthy to them. Only to me.

In her eyes, Snow left the village standing as a personal message to her about her actions and the pain he could cause her. However, there was also a side effect of doing this which was that any official Capitol citizens had somewhere to stay if they ever had need to visit District 12.
Comment: He does the same when they "bomb" 13 again, dropping Snow's chosen flowers, to relay a message directly to Katniss. A personal vendetta.


Brake performance after inactivity

Question: A 95 Integra 4dr was garaged \ unused for an extended period (10 months): it seems like one needs to 'stand' on the brakes. What causes this and how can it be corrected?
Answer: More than likely it's corrosion on the disk surface. Once it and all the dust from it is gone, the brakes should be pretty much normal, unless there is serious pitting or gouging from the corrosion.
You could pull your brakes apart and clean the surfaces of both the rotor and the pads. To do this, use a wire wheel brush (the type which goes on a drill; I'd use a cup type). Burnish the rotor surface on both sides. Then clean it with some brake clean and a clean shop rag. Just use the wire brush on the brake pads, then blow them off with air (wear a face mask if you do this). If you don't want to use air, brush them off the best you can. Then, reinstall as you took it apart.
The only other thing you can do is replace parts. Until the brakes are clean, your brakes will continue to exhibit poor performance. They can clean up over time, but how long that takes would be unknown.
Answer: If the vehicle has power-assisted brakes, the boost unit (vacuum or hydraulic) may not be operating. Sounds like your leg is taking the place of the power-assist. Check vacuum hose to power brake unit. Also, if either the front or rear set of brake calipers has seized up you are functioning with only front or rear brakes. Try low speed panic braking to a stop on loose gravel.  Get out and see if all four wheels have dragged through the gravel.

Brake performance after inactivity


The more you know, the more you don't know

Question: What is wrong with the following argument? The more you
study, the more you learn. The more you learn, the more you know.
The more you know, the more you forget. The more you forget, the
less you know. The less you know, the less you learn. So, why study?
Comment: It is customary to mention the source when quoting, as in this case, or, at least, to put the quote into the quotation marks. One thing wrong is that this quip is meant as a joke and not as an argument.
Comment: the question is so trivial that it should appear in the puzzle stack, imho. @Conifold it's a well known saying, i've seen it on postcards
Comment: "The more you forget" doesn't mean you forget everything you studied, thus you may still have a net gain in knowledge from studying.
Answer:
The more you study, the more you learn

Not completely true but a reasonable first order approximation.

The more you learn, the more you know

I'd agree with this on the basis that learning implies new or reinforced knowledge.

The more you know, the more you forget

Debatable. This assumes a fixed upper limit to knowledge and that it's possible to reach that limit.
Edit (thanks to Cubic). Or that knowledge has a relatively fixed probability of being forgotten. This is highly unlikely given what we know about memory reinforcement.

The more you forget, the less you know

True in the sense that you know less than you would if you didn't forget. It does not follow that you know absolutely less. That would depend on the rate of knowledge accumulation relative to knowledge loss.

The less you know, the less you learn

Not true at all. Young children learn at a prodigious rate for example. You could say the less you know, the less you had learnt or similar but that doesn't help your argument.

So, why study?

To learn more so that you can know more.
Comment: > This assumes a fixed upper limit to knowledge and that it's possible to reach that limit.

No, that's reading something in there that isn't there. The statement could just as well be interpreted as assuming that there's a set probability of forgetting any given fact, leading you to forget more things in absolute terms the more facts you know.
Comment: @cubic Fair point. I've edited to reflect this.
Answer: Student A learns, acquiring 5 units of knowledge.
Student A learns, acquiring 7 more units of knowledge.  He forgets 3 units of knowledge.
Student A learns, acquiring 4 more units of knowledge.  He forgets 2 unit of knowledge.
Student B learns, acquiring 3 units of knowledge.
Student B learns, acquiring 2 more units of knowledge.  He forgets 1 unit of knowledge.
Student A has learned 19 units of knowledge total.  He has forgotten 5 units of knowledge.  He retains 14 units.
Student B has learned 5 units of knowledge.  He has forgotten 1 unit of knowledge.  He retains 4 units.
Student A has forgotten more than Student B currently knows - but still knows more than Student B.
The problem with your reasoned progression is that you don't specify relative rates.  Now, in actual practice, amount of knowledge is difficult to quantify.  So is quality of knowledge!  But in general, if you have a container into which things are flowing in and out, the difference between the two rates has to be specified if you want to determine whether your container is filling up or emptying.