8,799 reputation
12041
bio website github.com/CodesInChaos
location Frankfurt, Germany
age
visits member for 2 years, 9 months
seen 2 hours ago

Mar
20
comment Even passwords are vulnerable to hash collision attacks?
The adversary can inject material (though the salt might block any collision attack). But such a collision attack at best(from his point of view) allows the attacker to create an account for which he knows two different passwords. Not very useful...
Mar
20
comment How does the rand() function in C work?
Even when eyeballing the plot of rand() it often exhibits total failure
Mar
20
comment How does the rand() function in C work?
Given the typical implementation of rand(), you're using a quite generous definition of "works". IMO it does not work, even for non security related stuff.
Mar
19
comment Brute forcing an HMAC
If it's a proper key (128 random bits) then it's completely infeasible. If the key is derived from a password, it depends on the password and the derivation function. But in that case you don't attack HMAC, you attack the password.
Mar
19
comment Encryption with Deduplication
This is known as convergent encryption. Unless your question has any aspects not covered by that question, we could close it as a duplicate ;)
Mar
18
reviewed Approve suggested edit on computing inverses in truncated polynomial rings manually for NTRU encryption
Mar
18
reviewed Approve suggested edit on When confusion is applied during encryption?
Mar
18
reviewed Approve suggested edit on Where to store the private key and the public key in a communication protocol
Mar
18
comment Efficient algorithm for remainder calculation over prime field for ECC implementation?
@venkat Primes in ECC are often specifically chosen so they allow more efficient reductions.
Mar
18
revised Efficient algorithm for remainder calculation over prime field for ECC implementation?
added 6 characters in body
Mar
18
comment Export from US of crypto software with key-size > 56 bits still needs permission?
You often need to register your software, but as long as you don't export to a couple of blacklisted states, that's mostly a formality. For open source software the rules are even more relaxed. So effectively it's just a bit of bureaucracy thrown at you.
Mar
18
awarded  Fanatic
Mar
18
comment How large should a Diffie-Hellman p be if the messages are encrypted?
You should also ask yourself what you're using DH for, if you already have a shared key? Forward secrecy?
Mar
18
comment How large should a Diffie-Hellman p be if the messages are encrypted?
Messages being encrypted doesn't make a difference. Just use a standard group designed for diffie-hellman.
Mar
17
comment How comparable is OFB to a one-time pad?
OFB is a synchronous stream cipher, and OTP is one as well.
Mar
17
revised Low Public Exponent Attack for RSA
added 45 characters in body; edited tags
Mar
16
comment Is AES-256 a post-quantum secure cipher or not?
The attack you link does not work when you use AES with a random key in a normal way. If you only need AES to be a pseudo-random-permutation (PRP), then it's no attack at all. AES was primarily designed as a PRP, resistance to related key attacks was only a secondary goal(if it was a goal at all). It is only an attack if you use AES in an unusual way where the attacker has control over the key. For example if you try building a hash function from AES, this attack might become an issue.
Mar
16
comment Is AES-256 a post-quantum secure cipher or not?
Calling a related key attack on AES "practical" isn't really true. The way AES is supposed to be used is with a random key. So this attack can't be used against any "normal" AES use.
Mar
11
comment Is there an efficient way to hide the encrypted plaintext length with a block cipher?
I don't get your question, but you can use AES-CTR as PRNG. Stream ciphers and the expansion part of a PRNG are essentially the same thing. But that way the only input will be the key.
Mar
11
comment Would a “Triple AES” (in the sense of how Triple Des works) serve for a dramatic increase in safety?
If were were to use double encryption, I'd go with AES xor ChaCha (or Salsa20). Tahoe-LAFS will use some variant of this for its 100 year crypto.