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Nov
26
comment Is the AES encryption scheme CPA secure?
AES is just a primitive. You should describe how you use it to build an actual encryption scheme. And how do you use the IV?
Nov
26
comment Is there an advantage to storing keys split between several hashes?
"but split the key into several parts and hash each of these parts" that'd be much easier to crack. Read a bit about LANMAN hashes.
Nov
23
comment Should we sign-then-encrypt, or encrypt-then-sign?
If the encryption is CBC, then you can probably use a padding oracle to decrypt the message, breaking confidentiality.
Nov
23
comment Should we sign-then-encrypt, or encrypt-then-sign?
@PavelOgnev For example if you sign first and then encrypt with AES-CBC, you're still open to padding oracles. And a malleable ciphertext with fixed plaintext can be a problem in some contexts.
Nov
22
comment Encrypting with private key in Public Key InfraStructure
How about reading PKCS#1 ?
Nov
22
comment Encrypting with private key in Public Key InfraStructure
1) MD5 isn't good enough for this 2) You forgot the signature padding. No padding, no security.
Nov
22
comment Should we sign-then-encrypt, or encrypt-then-sign?
I'm for signing first, and then encrypting with symmetric authenticated encryption.
Nov
22
awarded  Self-Learner
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?