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bio website github.com/CodesInChaos
location Frankfurt, Germany
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visits member for 3 years, 4 months
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Nov
22
revised Does a trace of SSL packets provide a proof of data authenticity?
deleted 291 characters in body; edited title
Nov
22
comment Does a trace of SSL packets provide a proof of data authenticity?
Don't cross-post. The second half of the question is off-topic here.
Nov
22
answered Does a trace of SSL packets provide a proof of data authenticity?
Nov
21
comment Can ElGamal encryption and ElGamal signatures be used together sharing the same key-pairs?
A Robust and Plaintext-Aware Variant of Signed ElGamal Encryption might be interesting, combining ElGamal encryption with Schnorr signatures.
Nov
20
comment NIST Standard for Advanced Encryption Standard Algorithm
crypto.stackexchange.com/questions/5287/…
Nov
19
comment Is this a valid real-time authentication scheme?
MAC=Message authentication code, not MAC address. So no spoof for you.
Nov
19
comment Is this a valid real-time authentication scheme?
Why so weird? Can't you simply have Cindy authenticate a statement "Alice has the following public key"? That authentication can either be a signature or a key-exchange+MAC.
Nov
19
answered Does a break in a collision resistance property of a hash function by definition implies an attack at the first pre-image attack?
Nov
19
comment Does a break in a collision resistance property of a hash function by definition implies an attack at the first pre-image attack?
I was asking about your definition of "break", if it means faster-than-bruteforce or fast enough for an attacker with a certain computational bound? In the second case, an ideal hashfunction obviously doesn't have your property, since finding a collision takes $2^{n/2}$ operations, finding a first pre-image takes $2^n$.
Nov
19
comment Does a break in a collision resistance property of a hash function by definition implies an attack at the first pre-image attack?
Did you mix up the two sides of your comparison? And what definition of "break" do you use?
Nov
19
revised Will varying plaintext compensate for a fixed initialisation vector?
added 67 characters in body
Nov
19
answered Will varying plaintext compensate for a fixed initialisation vector?
Nov
19
comment Using CBC with a fixed IV and a random first plaintext block
I'd postulate that the scheme is secure with predictable IVs such as counters as long as the number of encrypted blocks is below the birthday bound. The idea is that the AES primitive will never encrypt the same block twice. The failure when a collision happens might be more severe though.
Nov
19
answered Using CBC with a fixed IV and a random first plaintext block
Nov
18
comment Decrypt digital signature using RSA public key with openssl
"It is then signed using an RSA private key" With which signature scheme? PSS?
Nov
16
comment Why does OAEP have 2 rounds with 2 random oracles?
This is essentially an all-or-nothing transform.
Nov
16
comment Is it safer to encrypt twice with RSA?
Not sure if you can call $(m^{e_1})^{e_2}$ encrypting twice since that only works with textbook RSA. With real RSA, you'd add padding before each encryption, making the intermediate ciphertext too large for a single exponentiation of the second encryption.
Nov
16
comment Is it safer to encrypt twice with RSA?
If you know $e$, $d$ and $n$ you can efficiently factor $n$ to obtain $p$ and $q$. Once you know $p$ and $q$ obtaining $d_2$ from $e_2$ is trivial. See Can two different pairs of RSA key have the same modulus?
Nov
16
comment AES key padding
@mikeazo I avoid constructions with a non uniform key in most situations. I prefer some kind of hashing or KDF step in between.
Nov
15
answered AES key padding