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

Mar
2
revised Is solving a modular linear equation a hard problem when the coefficient is not an invertible element?
deleted 19 characters in body
Mar
2
answered Is solving a modular linear equation a hard problem when the coefficient is not an invertible element?
Mar
2
revised Can SRP be used with Elliptic Curves?
deleted 35 characters in body; edited tags
Mar
2
comment Why is CAMELLIA suddenly so widely used?
"reason for NSS's ordering" makes little sense. A server preferring unusual ciphers can simply choose a cipher that's lower on the client's list.
Mar
2
comment Is it safe for the ChaCha8 nonce to be deterministic?
While ChaCha doesn't have much documentation, you can look at Salsa20's documentation. They're almost identical.
Mar
1
comment Is it safe for the ChaCha8 nonce to be deterministic?
And chacha operates on 16 words with 4 bytes each. Iv setup sets the offset to 0, and sets the 8 byte nonce.
Mar
1
comment Is it safe for the ChaCha8 nonce to be deterministic?
Use a larger nonce. See XSalsa20. Will post more tomorrow.
Mar
1
comment Is it safe for the ChaCha8 nonce to be deterministic?
You're misunderstanding something. Input to the permutation is 64 bytes, but that includes key, stream-id(nonce), offset and a constant.
Mar
1
comment Timing attack on modular exponentiation
Depends on your implementation. A good implementation uses some technique to defend against side-channel attacks. Either by using the same operations no matter what the data is, or by using blinding.
Mar
1
revised While generating a random Elliptic curve what are the conditions i have to considerd?
added 17 characters in body
Mar
1
reviewed Approve suggested edit on Simple example for CP-ABE (Ciphertext policy attribute-based encryption)
Mar
1
reviewed Approve suggested edit on Are RSA signatures deterministic?
Mar
1
comment Can I combine two PRNGs to make use of more seed data?
There are some tricky points here, but they're not related to entropy or the PRNG. It might be possible that the side that needs to commit later, can generate many public keys, until the random wordlist has some desired properties(such as being similar to the original wordlist). Check out how ZRTP attacked this problem.
Mar
1
comment Can I combine two PRNGs to make use of more seed data?
In that case you have a ~128 bit security level, so a 160 bit PRNG is fine. Or you can hash your seed data, and use it as key for Salsa20.
Mar
1
comment Can I combine two PRNGs to make use of more seed data?
How large is the finite field/elliptic curve you ran you DH on?
Mar
1
comment Counter mode secure hash algorithm
Btw. constructing a MAC with such a property is much easier. We know several such MACs.
Feb
28
comment Efficient Symmetric Mutual Entity Authentication Protocol
Asymmetric crypto isn't that expensive, especially if you use ECDH instead of RSA. It's only an issue if you create really many connections in a short time (several thousand per second) or you're using a really weak device(embedded system).
Feb
28
comment Is SHA-1 collision free on data up to 20 bytes long?
@mikeazo 1) I used exist in the mathematical sense, where you can show that something exists, without being able to actually construct it. (If the claim that there are collisions is actually true, then there exists a short proof for their existance) 2) Not with probability 1. You need $2^{160}+1$ in the worst case. But it's quite unlikely it will need more than $2^{90}$ operations.
Feb
28
comment Is SHA-1 collision free on data up to 20 bytes long?
@mikeazo Technically the proof exists, but it's very expensive ($2^{80}$ invocations) to find it.
Feb
28
comment “Free” key exchange in a Ed25519 PKI?
Yes, we can do that.