Since all new crypto questions are manually being migrated to the crypto stackexchange, why can't all the 400 existing crypto questions be migrated there? Currently its quite confusing to have some solved questions here and some over there.

  • There are many questions in that link that have already been migrated or deleted. They have the tag [Migratd] or [Deleted] respectively bringing the total number down. Mar 19, 2012 at 13:57
  • There are many questions that should be here, and should be tagged "crypto", for the reasons given in several of the answers here. And as your list demonstrates, many new crypto questions are staying here and not being migrated. As discussed when Crypto.se was set up, it is for cryptographers, but many security questions related to crypto are best answered here by security folks who are focused on risk management or the practicalities of security.
    – nealmcb
    Mar 19, 2012 at 23:59

4 Answers 4


Well, I'm a crypto mod and here's my take, bearing in mind I have an interest in promoting crypto:

Don't migrate old questions.

Really. There's no point in moving questions around just because right now they fit the scope of one site or another better. They were on topic here at the time, the OP has either had a resolution to their question or not checked back to see the outcome; either way, we're all done with those questions and unless there is a major reason to dig them up and improve them, we can leave them around for others to read at their leisure.

On a purely practical note, retagging 400 questions is not my idea of a fun weekend. Whilst I think the influx of questions would make crypto look good, it'd be a huge cleanup operation.

One of the things I took out of the recent firestorm on Stack Overflow r.e. closing and moving old questions was that actually we should judge a question on the answers it has - not purely on the question. The podcast for SE discusses this idea in unlimited amounts of detail.

The same applies to crypto vs security for a crypto question. It isn't about defining an ontology and moving crypto questions to crypto.se - it's about the answers you'll get:

  • On Security.SE you're expecting a best-practices security-focused what-should-I-do-to-be-safe answer. If you ask about inventing your own crypto, you'll politely be told not to do that and instead directed to one of the many freely available crypto libraries, recommended reading, previous questions etc.
  • If you ask on crypto, you'll get a detailed explanation of the various pitfalls of your scheme, with reference to relevant results.

Another practical problem of migrating all these questions is that many of them have answers in the former category, not the latter.

Finally, if there's a crypto question here on security that is harmful to the internet in its content, that can easily be fixed by existing mechanisms we have for that kind of thing - in increasing order of severity comments, downvotes, closing, deletion, whichever applies (the idea being we'd hopefully educate the poster along the way so that they fix the issue, whatever it is :)).

  • Can you please migrate the ~20 questions that are probably better of there? Mar 19, 2012 at 18:17
  • 1
    @Jenko I'm just a normal user here - I can only move things out of crypto. It's up to the sec.se mods; I'd also suggest we should probably ask on meta.crypto to make sure they'll be well received as my voice alone isn't the deciding factor. I'd also suggest we go through them slowly - batch moving 20 or so questions will flood our home page, pushing just-asked questions out of the way. In principle, if they're really and truly needing a better answer on crypto, I've no problem with moving them - but I think we need to not cause too much upheaval.
    – user2213
    Mar 19, 2012 at 19:37
  • I've also pinged all the relevant mods in chat, who may have differing opinions to me, so they are all now aware.
    – user2213
    Mar 19, 2012 at 19:45
  • 5
    When Crypto first got into Beta, we had lengthy discussions on exactly this - as a large number of the crypto guys were in here as well (still are :-) - and @Ninefingers' take on it as described above was the supported consensus view throughout. If there are specific new or unanswered questions that make sense to migrate, let's do that, but I think we have managed a pretty good balance between us on the older ones.
    – Rory Alsop Mod
    Mar 19, 2012 at 20:39

I dont think that any question tagged with crypto should automatically be migrated to the crypto site. Certainly not all the new crypto questions are being migrated, and there are definitely some existing ones that shouldnt be.

I see the difference as questions about crypto, how to use it, what to use, key management, what security trade-offs there are, etc - are more ontopic here than on crypto.se.
On the other hand, questions that are inside the cryptographic algorithms, internals, etc are the ones that should be migrated.

In other words, the theoretical, "math-y" parts of crypto should be there, the engineering parts here. (No, I'm not saying that all of crypto is "just" theoretical.)

While there is definitely some gray area, it seems that most questions are clearly either here or there.
I think the simple guideline is: If it's a question for a cryptographer / cryptologist / academician, it's a crypto.se question. If it's a question for a security engineer / architect / auditor / consultant, its a sec.se question.


I am a fan of "compendium of knowledge" and see value in moving high value/point questions to the appropriate site. I also see your point on how it can be confusing. There is overlap, and there isn't a hard and fast rule.

On the other hand, questions with false, misleading information should be closed on the appropriate site with a link to the most relevant answer on the correct site. This will prevent a site like Stackoverflow from overwhelming a smaller niche site such as cryptography. An uninformed reader may follow the advice of the highest voted question, and do things the wrong way. That is a loss for them and a loss for the SE community.

Finally, I think that questions with low votes, low views should be migrated according to user demand. Any time a question is touched (edits, rewrites, or especially mod flag) then they should be re-tagged accordingly. The retagging process is a pain, so perhaps the flagger should include new proposed tags as well.

This is my perspective so far:

  • SO - for programming, language specific implementations
  • Sec.SE - for all engineering, network, security admin and corporate policy questions
  • Crypto - for issues dealing with crypto mechanics or implementation variances in various libraries/etc. Some Math questions here
  • Math.SE - for deeper math questions that are more theoretical than Crypto's scope

In response to Avid's note, I'm compiling a list of questions that are probably better off in crypto.se. Please feel free to add/remove from this list.

  • 1
    For most/all of these, it would probably have been better if they had originally been asked on Crypto.SE. But now that they are here and have received answers from this audience, I would not suggest migrating them at this point. I think we'd be better off focusing on new questions as they come in. Just my personal preference; others may feel differently.
    – D.W.
    Mar 19, 2012 at 22:29
  • 2
    Some of these have answers that are good for security.se but not crypto.se. And in some cases even the questions seems to be better of here (for example "Using Secure Remote Password without sending the username in the clear"). Mar 19, 2012 at 23:09

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