First of all, I do not think that having a signature layout is any good for its own sake. In most fields, few people (apart from your workgroup) will attend more than one of your talks and even those who will, will likely not notice the consistency of your layout¹ – unless it’s particularly memorable, which is almost certainly not a good thing². And even if somebody notices, they will likely (and hopefully) value the quality of your design more, let alone the quality of your content.

Considering the required work, there are two aspects: (1) Creating (or choosing) a layout and (2) Using the layout throughout your presentations.

Aspect 1 takes a few hours, if you are sufficiently apt with your presentation program (and it does not suck) and know some basics of graphic design (which I suppose you do, if you are asking such a question).
Mostly it’s selecting a colour scheme, one or two fonts and a default arrangement of your slides and realising them in your presentation program and in the programs you use to generate your figures.
Regarding the constraints of existing templates, remember that (unless your problems are very individual) if no templates are the way you want them, it is very likely that you should be careful what you are wishing for.
Also beware that the fact that you have to rely on (usually unknown) projectors imposes some constraints on your font and colour selections.

Aspect 2 will usually save you some time, whether you are using a prebuilt design or your own: For example, you are very likely to reuse some material – in particular figures. And if you care about your slides being consistent (which I suppose you do), you avoid spending some time in adapting colour schemes, for example. In particular, there is usually no benefit in switching designs.

From personal experience, I have spent some time in working out a design and have not regretted it yet.

¹ Just think about, how few people give horribly designed presentations and thus can be assumed not even to notice the flaws in their own presentations, let alone the qualities of your’s.
² As you should not notice good design that much.

Is there added value in having your own presentation layout and using it consistently?
In case of using SSL the certificate server has a primary key and a public key that is published to all clients - as far as I understood. So in this case when message is encrypted by public key (on client side) only the owner of private key (which is the server in this case) has ability to decrypt it.

But I do not understand how this works the other way, I mean when the message is encrypted by private key then does it mean that whoever has the public key can decrypt it? That would mean that only the messages toward the server are secured and messages which come from the server can be read by anybody with public the key.

Update:
in my case I have web server in DMZ hosts multiple web services (WCF), the clients are non-server application (they are standalone .NET application) reaching these web services via internet using https protocol.

My server has SSL certificate issued by Versign, the point is that my client do not have any type of credential and any machine with that application (or similar app) should be able to consume the services, the point is that the information passing between client machine and server must be encrypted and signed, so this is my question is having the certificate and using the transport security enough to make sure that nobody can read the messages passing between client and server or do I have to somehow come up with some kind of ad hoc client credential and add message security.
This link describes that SSL is good for Intranet and for internet message security is suggested why? what does happen if I only use SSL and no message security for the internet scenario?
