21,061 reputation
42675
bio website
location
age
visits member for 3 years, 5 months
seen yesterday

Jan
9
comment Can you help me understand the Common Modulus Attack in a Lucas Group?
I don't see how this answers the question. The question was "Do I need to perform this operation in the Lucas group? As it stands all of my values are scalar."
Jan
9
comment Break double encryption
I encourage you to read the FAQ on homework questions. In particular, the FAQ asks you to show your work: show us what you've tried so far, where you've gotten stuck, etc. See also Paŭlo Ebermann♦'s answer. The problem is your question is too much like "Do my homework for me" and not enough like "Here is my task, I already did this part, and I have now this problem. Here is what I tried, but which didn't work."
Jan
7
revised Properties of Ideal Straight P-Boxes
added 156 characters in body
Jan
7
comment Properties of Ideal Straight P-Boxes
@Thomas, P-boxes cannot (on their own) provide any diffusion, since they just re-order the bits.
Jan
7
comment Properties of Ideal Straight P-Boxes
@ponsfonze, this doesn't answer the question; it just repeats what Wikipedia says the definition of a "straight P-box" is, but it doesn't answer what properties an ideal one should exhibit.
Jan
7
revised Properties of Ideal Straight P-Boxes
added 2 characters in body
Jan
7
comment Properties of Ideal Straight P-Boxes
@PaŭloEbermann, I see that I mis-read the question; I thought it said S-box. A search on "straight P-box" finds that Wikipedia says a straight P-box is a permutation (reordering) of $n$ bits. It's just a transposition (re-ordering) of the bits. Still, "ideal" cannot be defined without reference to the block cipher in which it be used.
Jan
6
answered High Power Computing for Crypto Research
Jan
6
comment A proof-of-work random number generation system for Pokémon
@JoeZeng, that aspect of breeding doesn't seem problematic. You are just saying that some of the stats of a child are determined by the parent (copied from the parent), and some are random. So, use the PRNG only for the random ones; for the ones that are copied, copy them from the parent. When a user wants to participate in a tournament, they prove that all of their characters were generated properly, from the seed previously handed them by the tournament server. [...] To prove outputs were generated with seed $S$, the tournament server can recompute the outputs of the PRNG and compare.
Jan
6
comment A proof-of-work random number generation system for Pokémon
@JoeZeng, I don't understand what you mean by brute-force, in this context. The output of the PRNG is fully determined by the seed, which is in turn fully determined by the central server (and not under the user's control). So I don't see what there is to brute-force.
Jan
6
comment A proof-of-work random number generation system for Pokémon
@JoeZeng, my apologies for being dense, but I did not understand any of your explanation why breeding needs special handling. As far as what is meant by a "seed", you might want to read about cryptographic PRNGs and how they work. The short version is that they generate an infinite stream of outputs $(y_1,y_2,y_3,\dots)=G(S)$ as a deterministic function of a seed $S$. Given any subset of the $y_i$'s, you cannot predict any of the other $y_j$'s or the seed $S$ better than blind guessing.
Jan
6
answered A proof-of-work random number generation system for Pokémon
Jan
6
answered Properties of Ideal Straight P-Boxes
Jan
3
comment A proof-of-work random number generation system for Pokémon
@JoeZeng, You could use a predetermined algorithm, but if the user could modify the game software, the user could modify it to use a different algorithm (not the one you had in mind) or to use different inputs. Therefore, your approach is not going to be effective against that threat model. (See the 5th paragraph of my answer where I already address this.) I'll come back to the question I asked before: "What's your threat model?" I think you need to edit your question to clarify your threat model.
Jan
3
revised Why is asymmetric cryptography bad for huge data?
try to make the question less confusing.
Jan
3
answered A proof-of-work random number generation system for Pokémon
Jan
3
comment Odds of false error detection in a randomness test using the chi-squared test?
As I understand, this question is 100% statistical in nature (there's no cryptography). You have a chi-squared test with 16 bins, with $n=80$ or $n=128$ observations, and you're testing whether the observations appear to follow a uniform distribution on the 16 bins. Your test accepts the observations as uniform if the test variable is $\le 65$ and rejects them otherwise. You want to know the probability of false rejection. That's a purely statistical question; it might be better on Statistics.SE. They should be able to answer your questions about the validity of the approximation.
Jan
3
revised Odds of false error detection in a randomness test using the chi-squared test?
edited title
Jan
3
comment What's the strategy for future directions in cryptography? Bigger numbers/faster searching, or new methods, say, of factoring?
And, by the way, welcome to Crypto.SE!
Jan
3
comment What's the strategy for future directions in cryptography? Bigger numbers/faster searching, or new methods, say, of factoring?
The question body seems much narrower than the question title. Would you care to edit them to make them match? Are you asking "What are the future directions in cryptography?" (very broad) or "What is the likely future of public-key cryptography?" (you got a good answer) or "What are the future directions in breaking RSA?" (closer to what you ask in the body of your question).