10,784 reputation
11046
bio website vyznev.net
location Helsinki, Finland
age
visits member for 2 years, 8 months
seen 3 hours ago

I'm not really a cryptographer, I just play one on the internet.

Seriously, I'm just a programmer and mathematician interested in puzzles and information security. I don't have any kind of formal crypto training, but I've picked up a few things here and there over the years. Topics I'm particularly interested in include protocol design and analysis, classical ciphers and information-theoretically secure crypto techniques such as one time pads and secret sharing schemes.

Please consider any (original) code I post to Stack Overflow (and other Stack Exchange sites) to be released under CC-Zero unless stated otherwise. You may do whatever you want with it and don't have to credit me in any way, although of course that would be nice.


Aug
30
answered Why is the complexity of RSA-1024 80 bit and not 86 bit?
Aug
29
reviewed Close Am I insecurely implementing AES in Python?
Aug
29
reviewed Leave Open The security of an encrypt and MAC
Aug
29
comment The security of an encrypt and MAC
This seems very similar to this recent question. The only real difference I can see is that the other question explicitly specifies that k1 = RC4(k2).
Aug
29
accepted Does impersonating an SRP server give you enough information for an off-line dictionary attack?
Aug
29
revised How to hash a list of multiple items?
better title; rm sha-1 tag, not really relevant
Aug
29
answered How to hash a list of multiple items?
Aug
29
comment The security of an encrypt and MAC
It's not necessarily that impractical: you can derive the unique encryption and MAC keys from a master key and some nonce (e.g. a message number) using a KDF. Sure, changing the key for each message is probably slightly slower than using the same key for all of them, but then, if you're using HMAC you're presumably not aiming to squeeze every last bit of performance from your hardware anyway. (If you are, consider using a universal hashing based MAC instead.)
Aug
27
awarded  Nice Answer
Aug
27
comment RC4 system pitfalls
Your description seems to be missing some possibly relevant details. For instance, what key is used for the HMAC? Is the HMAC output also encrypted, and if so, how? And how are the segment lengths transmitted?
Aug
27
revised Should I delete cryptographic data from memory?
edited tags
Aug
27
reviewed Leave Open hardware and software optimizations for Salsa20
Aug
27
reviewed Leave Open Three-way key exchange with elliptic curves without pairing
Aug
26
comment The specification of modern, non-communicating cipher machinery
I agree with @owlstead, and have voted to close this question as essentially unanswerable. There might be a meaningful and practical question hidden behind it, but if you want it answered, you'll have to be more explicit about what it is. As currently written, I'm fairly sure the only kind of literature such questions have been considered in is science fiction and fantasy. (And for that, we have another Stack Exchange site.)
Aug
26
comment Lagrange Interpolation for finite field GF(2^8), for Secret Reconstruction
Is the result you're getting actually 104, not 14? Because that's what you should be getting if you calculate 17 × 3 + 34 × 3 + 61 in GF(2^8). The reason you're not getting 10 is that the points (1,17), (2,34) and (3,61) do not satisfy y = 5x² + 2x + 10 in GF(2^8). To make the reconstruction work in GF(2^8), you need to calculate the shares in that field too; see poncho's second answer for details.
Aug
26
comment Lagrange Interpolation for finite field GF(2^8), for Secret Reconstruction
If you're using operator overloading to implement Galois field arithmetic, remember that you need to overload addition and subtraction too. And don't forget to overload the non-assignment versions of the operators, either.
Aug
26
awarded  Revival
Aug
25
revised Multiplication/Division in Galois Field (2^8)
added 4 characters in body
Aug
25
revised Multiplication/Division in Galois Field (2^8)
added 1034 characters in body
Aug
25
answered Multiplication/Division in Galois Field (2^8)