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13h
comment Why do crypto libs use table lookups when they're vulnerable to timing attacks?
@user54609 bitslicing is only efficient for parallelizable modes.
2d
comment Is modular Barrett reduction usable for Ed25519?
The order is still pretty close to a power-of-two, so you can use a variant of the approach described at: What are the computational benefits of primes close to the power of 2?
2d
comment I need answer to this problem
Start with factoring n and then computing the private exponent d.
Jul
31
comment Point addition in NaCl/libsodium (Curve25519)
It's public domain if you copy it out of NaCl or SUPERCOP.
Jul
30
comment getting different wrong decryption points on elliptic curve
The question is lacking the details necessary to answer it. You didn't even specify how you use ECC to encrypt messages. ECIES, EC-ElGamal, etc.
Jul
28
comment Factorize RSA knowing several N and E
@Antimony While RSA moduli usually have two prime factors, that's not always the case. Using more factors improves the CRT speedup, but you need to be careful that the factors remain big enough so that elliptic curve factorization (whose cost depends on the size of the factors) is more expensive than GNFS (whose cost depends on the size of the modulus).
Jul
27
comment Point addition in NaCl/libsodium (Curve25519)
NaCl isn't an ECC library, it only offers higher level operations like key-exchange and signatures and doesn't have point addition in its public API. You should be able to find an edwards form point addition function in its Ed25519 implementation.
Jul
26
comment Show How to Efficiently Solve the Computational Diffie-Hellman Assumption given an Algorithm that Solves the Square-DH Problem
Related problem: Can we reduce Diffie-Hellman problem to “Discrete-log inversion” problem?
Jul
22
comment Question about the key in RC4
@lena What's your target hardware? The relative performance of ciphers varies a lot between different CPUs.
Jul
19
comment Why don't use random padding in RSA?
AFAIK what Yehuda described is called RSA KEM. I believe it comes with a pretty strong security proof.
Jul
18
comment How is an epsilon of 1/1000 non-negligible?
1) This question is about what it means for an attacker's advantage to be negligible. Your answer doesn't address that at all. 2) Exploiting a weak PRNG to factor an RSA modulus generated by it isn't related to brute-force. 3) If you're referring to the "many moduli have a prime in common" problem, that was caused by very badly seeded PRNGs outputting identical data of several hundred bits for the first request of random data. This is unrelated to small biases.
Jul
18
comment Why does “2xAES-256” provide “99.99%” security strength whereas “1xAES-128” provides “40%”?
@mikeazo Should I trust CipherCloud? has been closed and deleted. While this question isn't as as non constructive, it still has the "I want to criticize that product but must do it disguised as a question" trait.
Jul
18
comment Why does “2xAES-256” provide “99.99%” security strength whereas “1xAES-128” provides “40%”?
I'm closing this because it's not a genuine question about cryptography. It's a post designed to make fun of ridiculous marketing claims, just phrased as a question. If you enjoy debunking bad crypto, you might want to create a blog, similar to Bruce Schneier's doghouse.
Jul
18
comment Deterministic ECDSA signatures?
@DrLecter The OP wants verifiably deterministic signatures and already linked that RFC.
Jul
15
comment Where I can find a list of certified software / hardware RNGs compliant to NIST SP 800-22?
csrc.nist.gov/groups/STM/cmvp/documents/140-1/140val-all.htm might be relevant.
Jul
15
comment What good is a hash accompanying a program?
Related question on security.se: Does hashing a file from an unsigned website give a false sense of security?
Jul
15
comment Ephemeral Diffie-Hellman in a symmetric crypto context
Does the shared secret have high entropy?
Jul
15
comment AES-CBC pre-determined IV vs. null IV
Note that symmetric crypto means that key generators are possible. Using asymmetric keys only cracks but not key generators are possible, but they produce longer product keys.
Jul
14
comment how to implement order preserving encryption except cryptdb
Cryptdb is an implementation, not an algorithm. Are you really looking for an algorithm, or do you want an implementation? AFAIK cryptdb has an accompanying paper describing the algorithms it uses.
Jul
14
comment where to store the salt for “crypto_pwhash” in a web application with no local storage
@mikeazo I think this question would have been fine on crypto.se as well.