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May
25
revised Galois fields in cryptography
update
May
25
comment Galois fields in cryptography
<<*snip*>> - I've put this comment as an update to the question.
May
24
asked Galois fields in cryptography
May
24
comment Memory-hard operations in work-factor hash functions
@CodeInChaos I am using scrypt, in my production code. This is just something I'm playing with out of interest, to see how I might go about creating a memory-hard hash function.
May
24
comment After implementing a novel encryption algorithm, how would one go about analyzing its security or get help from others in doing so?
Can't +1 poncho's comment enough. Learn to break ciphers! I aso recomment Stanford's free crypto course.
May
24
comment After implementing a novel encryption algorithm, how would one go about analyzing its security or get help from others in doing so?
I think you misunderstood. I'm saying that you shouldn't use your own schemes in practice, for any form of security mechanism in a production environment. You can devise your own schemes and get critique to learn about crypto, but please don't ever use your own cipher to secure sensitive information. Real ciphers have been developed by serious crypto gurus and vetted by hundreds of other serious crypto gurus, over a period of many years. Not a single one of them would use their own cipher without years of peer review and revision.
May
24
asked Memory-hard operations in work-factor hash functions
May
24
comment After implementing a novel encryption algorithm, how would one go about analyzing its security or get help from others in doing so?
If you're considering them as an actual security measure, forget it. Crypto is a field where "rolling your own" is a very bad idea.
May
23
asked Is every output of a hash function possible?
May
23
comment Is it secure to use the hash of key as the IV in AES encryption?
@CodeInChaos It's not intended to be some hair-brained "increase the entropies!" scheme, if that's what you're concerned about. The idea is to xor the IV with the hash when storing it in the file, so it can't be known by an attacker without knowing the password.
May
23
comment Is it secure to use the hash of key as the IV in AES encryption?
A solution to this is to store a random IV in the file header, xor'ed with the hash of the password. When you decrypt, compute the password hash and xor against the stored value, then use the result as the IV. This gives you a safe way to store the IV, and a unique IV per file.
May
23
comment Order of cascaded ciphers
Just for reference, if someone sees this answer in future and wonders what custom hardware could crack DES, it's COPACOBANA: copacobana.org
May
23
comment What is the time complexity of the RC4 encryption & decryption algorithms?
Keep in mind, though, that time complexity is practically meaningless as a measure of speed in this sense, because it tells you nothing about how fast the cipher is. If it always takes 10 milliseconds to encrypt a block in a cipher, it's O(n). If it always takes 10 minutes to encrypt a block in a cipher, it's still O(n).
May
23
comment What is the time complexity of the RC4 encryption & decryption algorithms?
Most block ciphers will be O(n) against the number of blocks, yes.
May
23
asked Hash decrypts key, key decrypts cipher… why?
May
23
answered What is the time complexity of the RC4 encryption & decryption algorithms?
May
23
comment Order of cascaded ciphers
@PaŭloEbermann This is purely theoretical, so I'd be interested in the security implications of both.
May
23
comment Order of cascaded ciphers
Interesting. So the optimal solution is to place the two strongest ciphers on the outside? i.e. first and last.
May
22
revised Order of cascaded ciphers
added 69 characters in body
May
21
accepted Security of simple xor and s-box cipher?