<story><title>P1030680: Unbroken Enigma message (U534, 01 May 1945)</title><url>https://enigma.hoerenberg.com/index.php?cat=Unbroken&amp;page=P1030680</url></story><parent_chain></parent_chain><comment><author>edent</author><text>My favourite Enigma message - as told to me by a tour guide at Bletchley Park - was thought to be a stream of indecipherable gibberish.&lt;p&gt;Until a WREN noticed that the message never contained the letter Z.&lt;p&gt;One weakness of that generation of Enigma was that it could not self-encode a letter. That is, A was never encrypted to A.&lt;p&gt;This had no letter Zs. A statistical improbability. Unless, so she reckoned, the &lt;i&gt;entire&lt;/i&gt; message consisted of &lt;i&gt;only&lt;/i&gt; the letter Z repeated.&lt;p&gt;Apparently, their best guess was that a bored soldier sent a stream of Zzzzzz to a friend. That was enough to crack that day&amp;#x27;s key.&lt;p&gt;Of course, every guide at Bletchley has a range of stories they tell credulous geeks. But it is a delightful tale of how OpSec is everything.</text></comment>
<story><title>P1030680: Unbroken Enigma message (U534, 01 May 1945)</title><url>https://enigma.hoerenberg.com/index.php?cat=Unbroken&amp;page=P1030680</url></story><parent_chain></parent_chain><comment><author>jfengel</author><text>At this point, how long would it take to brute-force an Enigma message on a modern home computer? Is it on the order of hours, or millennia?&lt;p&gt;I found this:&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;crypto.stackexchange.com&amp;#x2F;questions&amp;#x2F;33628&amp;#x2F;how-many-possible-enigma-machine-settings#:~:text=Wikipedia%20is%20your%20friend%3A%20%22Combining,159%20quintillion)%20different%20settings.%22&quot; rel=&quot;nofollow noreferrer&quot;&gt;https:&amp;#x2F;&amp;#x2F;crypto.stackexchange.com&amp;#x2F;questions&amp;#x2F;33628&amp;#x2F;how-many-po...&lt;/a&gt;&lt;p&gt;which says the key space is something like 10^20 or 10^23.&lt;p&gt;A modern supercomputer does something like 10^18 FLOPS. I assume that an enigma decryption is considerably more than a single floating point operation, but presumably just a few orders of magnitude.&lt;p&gt;So... if I&amp;#x27;m reading that right, we&amp;#x27;re talking about months, perhaps?</text></comment>