Decryption of ciphertext

Question

On both StackOverflow and at the healthy beta Cryptography we get a lot of questions about decryption of a certain ciphertext. Sometimes they are just base 64 blocks, but often there is a bit more to it than that. On neither site they are on topic.

Do you allow such questions or are they considered off topic? If they are on-topic, what would be the minimal requirements for said questions? Note that there would be quite a few persons that have a ciphertext because of a hack or because they just want to decrypt a random binary.

Strictly optional question: If they are off topic, would you know a place where they could be posted instead?

Anyway, good luck with the beta!

Answer 1

I think this largely depends on the way the question is phrased. I assume a large number of people post a ciphertext from their homegrown algorithm and want you to give them back the plaintext? That wouldn't really be on topic here in my opinion.

What would be on topic would be if they've found some ciphertext and have actually gone to some length to try to understand the algorithm and decipher it. Even better if they also have both a ciphertext and corresponding plaintext as well as an algorithm in either code or hardware description but have a hard time figuring out some specific part of the code or hardware. The question should also be such that the correct answer wouldn't be many thousands of words.

Simply providing a ciphertext without an algorithm would be a waste of everyone's time in my opinion. We wouldn't want to turn into a cryptographic land fill.

There seems to be some sort of issue with meta for me. I can't actually log in which might be why no one else has responded.

Answer 2

I think posting ciphertext is totally fine. If we want to develop techniques to decode/decrypt/deobfuscate, we will need diverse examples.

You have some unknown binary data and you don't know what it is?

If this isn't the forum for it, what is?

I find it more than a little humorous that xoring 4 bytes across a stream makes IDA users lose their chill.