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Jul
10
comment Entropy of system data - use all and hash, or trim least significant bits?
@CodeInChaos That's the part I don't really understand. The Wikipedia article is a little vague.
Jul
10
comment KDF with low-entropy salts
@CodeInChaos If the salt is predictable (e.g. user ID from database auto-increment) an attacker could trivially generate small rainbow tables for each user.
Jul
10
answered KDF with low-entropy salts
Jul
10
comment Entropy of system data - use all and hash, or trim least significant bits?
@CodeInChaos I'd never heard of it. So I use hash(entropy) as the key and compute AES(counter, key) where the hash is the key? Not really sure I understand the rest of the protocol.
Jul
10
revised Entropy of system data - use all and hash, or trim least significant bits?
better explanation
Jul
10
asked Entropy of system data - use all and hash, or trim least significant bits?
Jun
6
comment Is there a simple hash function that one can compute without a computer?
You can improve your chance of picking a prime by using the 6k±1 rule. Note that this rule only applies one way - all primes fit the rule, but not all numbers that fit the rule are primes.
May
30
comment Applying multiple hash functions to improve security?
Multiple iterations of the same hash is often useful. However, Ha(Hb(Hc(Hd(message)))) is only as strong as the weakest in the chain.
May
30
comment Cryptographic Algorithm/Protocol needed
@esskar Don't bother spending money on draconian DRM that won't actually do anything. Instead, get a lawyer to draft up an NDA for all staff that have access to your valuable assets (e.g. source code, design specs, etc) and implement strong working practices to ensure that data can't be leaked accidently. Keep an air-gap between your development network and your internet-access/email network. That way, you can take disciplinary action if someone violates procedure, or legal action if someone violates their NDA.
May
27
answered Brute force a ciphered message?
May
27
accepted Galois fields in cryptography
May
27
comment Galois fields in cryptography
This is an amazing answer. I get it now! :)
May
26
comment Is it secure to use the hash of key as the IV in AES encryption?
@CodeInChaos Paranoia! :)
May
25
comment Galois fields in cryptography
I'm still lost. I understand vectors as a small set of numbers. So, a vector has a size and a set of values - essentially an array. A vector $[a,b,c,d]$ has a length of 4 and four values - $a$, $b$, $c$, and $d$. If a field is a set of vectors, I envision it as: field = array(array(a1,b1,c1,d1),array(a2,b2,c2,d2),...). Is this correct? If so, how are a1, b1, etc. computed initially, ignoring operators? Or do we just populate them with something (e.g. a key) and then do operations on them?
May
25
accepted Standard symbol / notation for “x knows y”, or the inverse
May
25
comment Standard symbol / notation for “x knows y”, or the inverse
@CodeInChaos I was just using it as an example. If I were really writing that in a document, I'd put something like "where $f(x)$ runs in polynomial time or better".
May
25
comment Standard symbol / notation for “x knows y”, or the inverse
So you're saying there's no such notation?
May
25
asked Standard symbol / notation for “x knows y”, or the inverse
May
25
accepted Is every output of a hash function possible?
May
25
revised Galois fields in cryptography
example