21,096 reputation
42675
bio website
location
age
visits member for 3 years, 6 months
seen 21 hours ago

Sep
30
answered Friedman Index of Coincidence, pruning multiples of the keylength
Sep
30
comment how to mathematically prove a key exchange algorithm
Welcome to Crypto.SE! Unfortunately, this question is probably too broad and open-ended to be a good fit for this site. What have you studied so far? What's the real problem you have in front of you? What's the context and motivation for your problem? Providing a more detailed and narrowly focused question makes it more likely that it will be possible to provide a useful answer, within the constraints of a StackExchange site.
Sep
30
comment Friedman Index of Coincidence, pruning multiples of the keylength
OK. I suspect, when the IC was invented, it was typically used together with human judgement, so there might not be any standard rules to address this issue. Anyway, it seems like it might be easy to add a special case for this situation: choose the one with the highest IC, except that if it has a divisor whose IC is within 5% of it, choose the divisor. Another plausible solution would be to try running the rest of your attack on both candidates. I would imagine either of these might work fine. Have you tried either of these approaches?
Sep
30
comment Friedman Index of Coincidence, pruning multiples of the keylength
Do you need a solution that is 100% automated (no human involvement), or are you OK with involving human judgement? If the latter, it seems pretty easy for a human to recognize this situation and choose the smaller keylength.
Sep
30
revised Are NIST's changes to Keccak/SHA-3 problematic?
added 57 characters in body
Sep
30
comment Are NIST's changes to Keccak/SHA-3 problematic?
Personally, I am skeptical that there is anything to worry about here, but I'm interested in a better answer about whether we should be concerned.
Sep
30
asked Are NIST's changes to Keccak/SHA-3 problematic?
Sep
28
comment How to attack a fixed LCG with partial output?
@nightcracker, I think it does mean that. A $2^{16}$ attack means the generator is broken. It means absolutely no one should use the generator. At that point, who cares whether there is a $2^8$ attack? How will that affect your decision-making? If news of a $2^8$ attack will cause you to avoid the generator, when news of a $2^{16}$ attack wouldn't, then there is something wrong with your decision-making. P.S. If your question is about other generators like the Windows rand(), but different (say with larger parameters), then that's a different question: post a new question.
Sep
28
comment How to attack a fixed LCG with partial output?
@nightcracker, in that case, it sounds like your question is not about cryptography per se, so I don't think it is on-topic here. The cryptographic aspect of the question has been answered....
Sep
28
revised How to attack a fixed LCG with partial output?
added 1224 characters in body
Sep
28
answered How to attack a fixed LCG with partial output?
Sep
27
awarded  Nice Answer
Sep
27
awarded  Nice Answer
Sep
27
answered What are the possible cryptographic implications of Zhang's proof of the Twin Prime Conjecture?
Sep
27
comment How much does a successful Distinguishing Attack “break” the attacked stream cipher?
It sounds like your real question is: "Does a distinguishing attack count as a complete break, from a practical perspective?" If so, you might want to re-write your question from this much more general perspective (whether it's a linear distinguishing attack or some other distinguishing attack is probably of limited relevance).
Sep
27
comment How does Dissent protect against Sybil Attacks?
Have you read the research paper? That would be the best place to start, for this sort of question. (Often presentations don't include all of the detail; a lot of details are left to the paper, so you really need to read the paper if you want to answer detailed questions like this.)
Sep
25
comment Is this a structural weakness of Feistel networks?
pg1989, Ahh, now I see: you are uncertain about the definition of diffusion. The definition of diffusion is that each bit of the input affects all bits of the output. For instance, if you flip one bit in the input to the block cipher, then about half of the bits of the output of the block cipher should change. Notice that this doesn't impose any restrictions on what happens internally, inside the block cipher; it only has to do with how the inputs ultimately affect the final outputs of the cipher. See the strict avalance criterion.
Sep
25
comment How broken is a xor of two LCGs?
Many thanks, @fgrieu! You're right, that wasn't right. It should have been "top 40 bits of $x_0$", not "bottom 20 bits of $x_0$". Fixed. Thank you for spotting that!
Sep
25
revised How broken is a xor of two LCGs?
fix error. thanks, fgrieu
Sep
25
reviewed Excellent Will our app be FIPS 140-2 compliant if we use our own AES algorithm implementation?