Cryptography is a very old subject in History and while many people concentrate on the Computer Age cryptosystems, quite a few people can be interested in older cryptosystems like oldish ciphermachines (Enigma and Purple come to mind) or even ancien paper-and-pencil based ones (ADFGVX and others). Do we want discussion about these as well?
$\begingroup$ Thanks all, I just re-tagged the Playfair question with "Historic". Main reason I asked this question: stackoverflow.com/questions/495172/… and dev.keltia.net/projects/old-crypto $\endgroup$– KeltiaJul 19, 2011 at 21:27
I would say, yes, they should be allowed.
For now, the only such question I found is the one about the Playfair cipher, and it seems fitting here.
Maybe we could use a tag like historic for all such ciphers invented before the computer age?
I think it would be tragic if this site were to focus only on Modern Crypto. There are so many interesting ideas in the older cryptosystems, and this is truly the best arena out there for such questions.
Besides, would it hurt the site? I think not - I think CryptSE will only benefit from encompassing all cryptography.
$\begingroup$ It's also worth noting that classical/historical ciphers play a huge part in learning to understand cryptography. It's a lot easier to get early concepts like frequency analysis across to someone who isn't familiar with them when you use examples they can do in their heads or on paper, rather than hiding it all in a computer before they've wrapped their brains around it. $\endgroup$ Jul 25, 2011 at 18:01
$\begingroup$ Good point. I certainly started with classical ciphers. I wonder if there are many who don't... $\endgroup$ Jul 25, 2011 at 18:43
I think questions about older systems may be acceptable as long as they are "tell me about X" and not "let's talk about X".
To make this a strong site, we will have to ask and answer good questions about cryptography. As tempting as it may be to allow borderline questions, we'll have to remember that future visitors to the site will use existing open questions as justification for new ones. Accepting a weaker question because it expands the base knowledge of the site is an invitation to a stream of similarly weak questions.
I agree with Paŭlo that the Playfair question seems to be a good one, and if we can get more questions about older systems that are also good questions for an SE site, then I would vote them up as well.
2$\begingroup$ Let's talk about questions should be off topic for modern ciphers, too, shouldn't they? $\endgroup$ Jul 19, 2011 at 23:09
1$\begingroup$ Yes, they're simply not the type of question that works well in this format. $\endgroup$ Jul 20, 2011 at 0:03
I find the historic questions interesting and nominally relevant and I definitely would like them to be part of the site.
But I'm sure I'm not the only intermediate-level enthusiast professional who's a little bit annoyed with the undue depth of coverage which is often devoted to pre-digital cryptography, seemingly at the expense of the far more relevant modern topics. No doubt it's much easier to make this material approachable when you can relate it to non-programmers with a pencil and paper, so more of it gets written.
So let's just make sure the stuff of the past doesn't overwhelm the discussion to the point that it obscures the knowledge about current and future cryptography.