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bio website github.com/CodesInChaos
location Frankfurt, Germany
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visits member for 2 years, 9 months
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Nov
29
revised Message authentication codes construction
deleted 153 characters in body
Nov
29
comment Can someone tell if my Hand Cipher is secure?
Your real problem is "By my other cipher", because I'm 99% sure that the other cipher sucks, and obviously you need to generate a new pad for each message. Like with most stream ciphers, pad reuse is absolutely fatal.
Nov
29
comment Can someone tell if my Hand Cipher is secure?
Are your random numbers uniformly distributed between 00 and 99? In that case this part of the system should be secure but inefficient (ciphertext is twice the size of the plaintext). Simple modular addition is better. Essentially an inferior method for combining a keypad with a message, similar to stream ciphers/one-time-pads.
Nov
29
comment What cipher mode is suitable for independantly decryptable short messages?
Side-node: Compressing audio easily leads to side channel attacks.
Nov
27
comment Safety of DSA key parameters sharing
"it will likely be able to find a collision between the pairs you and she generated" [citation needed] For a reasonable security level that seems exceedingly rare (never happens in practice)
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 Why shouldn't one build a MAC by XORing multiple message blocks?
Order would be the least of my worries. The attacker can completely choose all but 1 message.
Nov
19
comment Is this a valid real-time authentication scheme?
MAC=Message authentication code, not MAC address. So no spoof for you.