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visits member for 3 years, 5 months
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I'm an engineer with experience in applied cryptography, in particular in Smart Card systems.


Jan
19
reviewed Approve How can I implement modulo 2^32?
Jan
16
comment How does bitmessage encryption work?
Relevant but very short on details: Jonathan Warren's Bitmessage: A Peer‐to‐Peer Message Authentication and Delivery System. $\;$ Current "official" protocol specification, but actual spec seems to be the code. $\;$ A (somewhat dated but still relevant) critic.
Jan
14
comment Factors of RSA modulus
Is there a simple proof that at least 3/4 of the possible $m$ values will result in a factorization?
Jan
14
revised Factors of RSA modulus
fix typo
Jan
13
comment The perfect way of using IV in CTR mode
A perfect way to send the IV is in clear before the ciphertext. Why use anything more complex?
Jan
10
awarded  block-cipher
Jan
9
revised Which block cipher mode does the experts use?
Polish
Jan
9
answered Which block cipher mode does the experts use?
Jan
9
comment Are there any known inverse hash lookups for the zero string?
This would be a first-preimage attack; I'm quite positive that we do not know a numerical answer for either MD5 or SHA-1, and I'm not aware of one for MD2 or MD4 (although there are theoretical preimage attacks on these hashes).
Jan
8
revised Sophie Germain primes and safe primes
typo
Jan
7
comment Sophie Germain primes and safe primes
@Tito: I (and most on this website) would rather not give direct answer to what could be homework. $\;$ Beside, you ask for 2048 and 4096-bit Sophie Germain primes in you last comment, versus 2047 and 4095-bit in the question (given that the size stated in the question is for the safe prime); so I'm sure neither of if you ask specific values for a legitimate reason, and exactly what bit size they should have.
Jan
7
revised Sophie Germain primes and safe primes
Give better method
Jan
7
revised Sophie Germain primes and safe primes
typo
Jan
7
answered Sophie Germain primes and safe primes
Jan
5
comment Are there cryptographic hash functions which do not have any collisions?
@Thomas, a nitpick: pers FIPS 186-4, the input domain of SHA-256 (widely acknowledged to be a cryptographic hash function) is bitstrings of less than $2^{64}$ bits, which is a large but not infinite domain.
Jan
5
comment Performance bottlenecks in Paillier encryption
@absinthe: if there is such trick, I don't know it.
Jan
5
revised Performance bottlenecks in Paillier encryption
Give equation for Paillier encryption
Jan
4
answered Performance bottlenecks in Paillier encryption
Jan
4
comment Transforming a key into a seed with the most entropy
To turn a password into a key, you need to perform key stretching using a Password-Based Key Derivation Function. Examples (from passable to good) are PBKDF2, BCrypt, and Scrypt. Anything lesser (like a hash) will be terribly vulnerable to password guessing. $\;$ (update) Turns out Giles just said it!
Jan
2
comment How much extra information is in an RSA public key?
Uh, no. All 2048-bit primes have the same size in ASN.1: '02' for int, '82 01 01' for the 257-byte size, '00' for sign, followed by 256 bytes with the value, starting with a byte in range '80..FF'. Also the question is about public keys, which contain a large composite $n$, and $e$ which often is prime but needs not be.