Thomas

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	2,729 reputation	bio	website		visits	member for	1 year, 4 months
1320 badges		location	Wellington, New Zealand		seen	45 mins ago

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11h	comment	What is U2FsdGVkX1? And just for completeness (since the quote only answers half of the question) starting the files with "Salted__" does not give away information beyond the fact that the file was encrypted with (or at least for) OpenSSL, which is assumed to not be secret. So it isn't insecure.
11h	comment	Is a small size block cipher usable? For 32-bit block sizes I think a few hundred megabytes of output should be sufficient to distinguish between a CTR keystream and a random function, actually, assuming the plaintext has sufficient structure.
1d	revised	Is there a hash function which has no collisions? added 6 characters in body
1d	comment	Is there a hash function which has no collisions? @improv32 I understand. No, there isn't, under the standard definition of "hash function". But there are certainly one-way, collision-free functions, as CodesInChaos mentioned in a comment.
1d	revised	Is there a hash function which has no collisions? added 374 characters in body
1d	comment	Is there a hash function which has no collisions? @improv32 Hash functions can do that in what is called a commitment scheme. Why do you require the "no collision" property? Or did you really mean, "with a negligibly low chance of collision, which then is what cryptographic hash functions are for in that while there are infinitely many collisions, it is very hard to find one either accidentally or on purpose"?
1d	revised	Is there a hash function which has no collisions? added 688 characters in body
1d	answered	Is there a hash function which has no collisions?
1d	reviewed	Approve suggested edit on prime-numbers tag wiki
2d	comment	How to build an electro-mechanical public key cipher machine? @Manuel I agree those would be better fits for such computers.
Jun 16	comment	Factorization wanted `msieve` will get the job done in a week or two. I left it overnight with two threads and it had 13000 relations on ~260k, I can't have it running that long (let's just say I'm overdue for thermal paste renewal) but you could give it a shot on a few computers. There's also a GPU implementation but it's for CUDA so I can't tell if it's faster.
Jun 16	revised	How to build an electro-mechanical public key cipher machine? edited tags
Jun 16	comment	How to build an electro-mechanical public key cipher machine? I don't see why not. Even mechanical computers were Turing-complete in that they could be built to accommodate any series of instructions, so even elliptic curve cryptography could theoretically be built from vacuum tubes and rotors. Now, as for efficiency..
Jun 14	comment	Recommended authenticated stream cipher for minimum overhead? If it were possible to have zero authentication overhead, authenticated encryption schemes would already be doing it. You won't find your solution at this low a level, you need to go up a notch and design your system around minimizing overhead.
Jun 14	comment	Recommended authenticated stream cipher for minimum overhead? Yes, of course. But, no, a MAC always requires extra information. Think about it - if you have X bits of plaintext to encrypt and authenticate, and Y bits of output, at the very least X = Y to ensure correct decryption (pigeonhole principle) which leaves nothing for authentication. So Y > X. So, no, any authentication mechanism will always add a few bytes of overhead to store the fingerprint. So your options are in making the fingerprint smaller (not ideal for obvious reasons) or authenticating more data per fingerprint.
Jun 14	comment	Recommended authenticated stream cipher for minimum overhead? You will still have the same overhead with an authenticated stream cipher. They still have a message fingerprint, the strength of authenticated modes of encryption is in safely coupling encryption and authentication. AES-CTR is a stream cipher, by the way. If your packets are so small, are you sure you need to authenticate them all as they are received? Perhaps you could batch the authentication step if the packets are sent at a high rate, to alleviate the space overhead issue?
Jun 13	comment	How can I tell what symmetric algorithm my browser is using? Flagging for migration to Sec.SE too since that's really where this question should be :)
Jun 13	comment	How can I tell what symmetric algorithm my browser is using? In Chromium you click on the green padlock and go to the "Connection" tab, it shows which cipher suite is being used.. I would guess it's more or less the same for every other browser (given that they are basically all clones of one another now)
Jun 13	comment	Why is it impractical to generate a semiprime dictionary? That's okay. I'm sure a few external hard drives will be more than enough... perhaps not.
Jun 12	revised	Given a private RSA key, how do we get the public key? added 232 characters in body