8,839 reputation
12041
bio website github.com/CodesInChaos
location Frankfurt, Germany
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visits member for 2 years, 9 months
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1d
comment How can compute execution time for generate key AES algorithm?
I suggest using proper indentation.
1d
comment Will hashing over and over eventually give the same hash?
You will end in circles. I believe the average circle length is $\sqrt{N}$ when there are $N$ possible values. There are many such circles, once again approximately $\sqrt{N}$.
1d
revised How to use MSG_MORE and MSG_OOB with AF_ALG while computing hash on a big file?
deleted 10 characters in body
1d
comment How to use MSG_MORE and MSG_OOB with AF_ALG while computing hash on a big file?
This is a programming problem and thus belongs on stackoverflow
1d
comment HMAC definition by using only one key
See “Weaknesses” in SHA-256d? and Dodis, Y., Ristenpart, T., Steinberger, J., & Tessaro, S. (2012). To Hash or Not to Hash Again? (In) differentiability Results for H2 and HMAC
2d
comment Compared to GCM or XTS modes, how secure is H xor R1, E (R2, R1, Message) for confidentiality and integrity?
Authenticating the plaintext is risky. You can easily suffer from padding oracles and similar attacks (via timing side channels, error messages, etc.). We prefer encrypt-then-mac algorithms nowdays to avoid these issues.
2d
comment Compared to GCM or XTS modes, how secure is H xor R1, E (R2, R1, Message) for confidentiality and integrity?
XTS is an unauthenticated mode, so it does not detect modifications of the ciphertext. It only limits how well the attacker can predict the plaintext corresponding to the ciphertext they produced.
2d
comment Use cases for CMAC vs. HMAC?
Hashes usually faster than block ciphers sounds weird. After all most hashes are built from block ciphers and have stronger requirements than PRPness. Could be a historical accident since hashes are commonly ARX based, which is efficiently implementable in software, but that's no inherent property of hashes.
2d
comment Burn after read algorythm. Software verification on compromised environment. Software smart card
Intel seems to be working on something that could enable such functionality in future CPUs. (But Intel itself could still subvert it and it obviously can't prevent the analog attack)
2d
comment Is less security required for a short stream cipher than for the AES enciphering of very long messages?
What exactly is your question?
2d
comment Is less security required for a short stream cipher than for the AES enciphering of very long messages?
Why would you use a system that doesn't fulfill strong security notions when they are easily available and still very fast? Figuring out if certain weaknesses apply to your use case is hard and error prone. Pretty much the only exception are hand ciphers where you need to be able to encrypt/decrypt a message without a computer.
2d
comment Which algorithms are used to factorize large integers?
Your definition of L doesn't match wikipedia. You put the $^{1-a}$ at the end of the expression, wikipedia put it on $\log \log n$.
2d
comment Stateless hash based public key cryptography?
[tahoe-dev] Hash based Signatures for Tahoe LAFS. Seems to contain a working implementation of one of those unlimited tree signature schemes. If you like Merkle Trees you should talk to the TahoeLAFS people.
Apr
21
revised Creating passwords that are both secure and memorable
edited title
Apr
21
comment Creating passwords that are both secure and memorable
There are several similar questions on Information Security: What is your way to create good passwords that can actually be remembered? and What is a good algorithm for memorizing a password in a few minutes?
Apr
21
comment Creating passwords that are both secure and memorable
This question appears to be off-topic because it is about memorization techniques and not cryptography.
Apr
21
comment Security of KDF1 and KDF2 (hash based KDF's)
This should work as long as the message being hashed has constant length (or at least is prefix free). Else length extensions might bite you.
Apr
21
comment Simple digital signature example with number
Which part did you correct? The only difference I see is that you're using mod n as an operator and mike uses congruence mod n.
Apr
21
revised Recommendation for authenticated ephemeral key exchange
deleted 41 characters in body
Apr
20
revised Decrypting a small Message using RSA with a Private Key
deleted 16 characters in body