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Feb
3
comment Determining Involutary Keys in Substitution Ciphers
For small values of n, that's easiest. For larger, I think you can use the factorization of n.
Feb
3
revised Determining Involutary Keys in Substitution Ciphers
expand on multiple solution case
Feb
2
answered Determining Involutary Keys in Substitution Ciphers
Jan
24
awarded  Quorum
Jan
14
comment infinite one-time-pad based on reference compression. can this be made more practical?
Is this a question?
Jan
11
comment Is finding collisions in a part-hash not often enough a bad problem?
Come to think of it, I should say that this hypothetical "truncate and xor" function would exhibit collisions as long as you generated proper random inputs of say 64 bits. The collision condition is that they match in the first 32 bits. A test like for (int x=0; x<=MAX_INT; ++x) {ComputeHash(x);} is not good enough to trigger it.
Jan
11
comment Is finding collisions in a part-hash not often enough a bad problem?
@IamNick It would not be appropriate to model that hash as a pseudo-random function.
Jan
11
comment Is finding collisions in a part-hash not often enough a bad problem?
@Thomas That's what I was thinking as well. Any deviations from uniform distribution should result in more collisions. It would require some unusual interactions between the "random" test data and the hash function to make collisions less likely than the PRF model predicts. It seems more likely that there's a bug in the collision counting code.
Nov
11
comment Why can't I reverse a hash to a possible input?
Finding inputs that satisfy a boolean equation is not easy, and is generally known as en.wikipedia.org/wiki/Boolean_satisfiability_problem
Oct
30
answered How to convert RSA public keys to one key to use for text hashing?
Oct
9
comment How does perfect hash function works?
It depends what you mean by "key". But as the Wikipedia article notes, if you use a perfect hash function in your hash table you don't have to worry about collisions. So a key into another data structure is a common use case.
Oct
9
comment How does perfect hash function works?
"Perfect" means the hash can't assign two pigeons to the same hole, so you need at least as many holes as pigeons. And we knew how many pigeons we had when we designed the hash, so we don't have more holes than pigeons. That is, you can't give me a pigeon that wasn't in the original set and ask me where to put him. As @otus says, the hash is an algorithm, so you can run it on your parrot; but whatever hole it tells you will already have a pigeon in it.
Oct
8
comment Hypothetical encryption technique, is it secure?
What are the advantages of this over using any existing encryption algorithm? Certainly not efficiency.
Sep
4
answered Possibility of the encrypted text being the same as the supplied plain text!
Aug
12
comment Can one construct OTPs without using XOR?
Ah, you're right. I missed that it was also excluded from the message.
Aug
12
comment Can one construct OTPs without using XOR?
You're off by 1 in the prime case of construction 1; 0 has no multiplicative inverse. I think you noted that but then miscounted.
Aug
6
comment SSL pinning - how to safely hide the certificate?
You only need to validate that the client received the correct cert. The server won't send the private key so that can't be part of what the client validates. Consider just using a hash or thumbprint.
Jul
28
comment Why calculate pi to estimate randomness?
@FlorianBourse the binary representability of the value being approximated is not relevant. Simpler tests like checking lsb or msb can be seen as a random estimation of 1/2. And of course the test must be able to evaluate how close the estimate is to pi, so it needs a sufficiently precise representation of the actual value.
Jul
24
comment Can a 1 byte difference in AES 128 bit keys make huge difference in output?
A single bit difference in the key (or the plaintext) should result in a totally unrelated output. Any correlation would be considered a weakness.
Jul
10
comment Salting in asp.net?
A different random salt is generated when the user account is created (or possibly when a password is changed). You typically store it in the database with the password hash. crypto.stackexchange.com/questions/1776/…