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I'm an engineer with experience in applied cryptography, in particular in Smart Card systems.


Nov
16
answered Checking both Quadratic residuosity and Jacobi symbol simultaneously and efficiently
Nov
16
comment Block cipher to encrypt 8 bytes/64 bits - Use 64 or 128 bit cipher?
If you use a block cipher in ECB mode, the same plaintext will always lead to the same ciphertext, allowing to detect if the same plaintext is sent twice, which is against the security goals assigned to a cipher, and why good block ciphers operating modes use IVs. $\;$ Also: it would not be the first time when "requested to encrypt" should be understood as also requested to protect against malicious alteration. $\;$ Before choosing the block size of the cipher, find your goals, and what cipher or/and MAC or/and authenticated encryption you want to use.
Nov
16
comment What is the most computationally efficient way of generating pseudo-random permutations?
@user44353: You have found my intend! I fixed the typos that you kindly pointed. I'll provide a reference implementation in C and test values when time allows.
Nov
16
revised What is the most computationally efficient way of generating pseudo-random permutations?
Fix awful typos in the round function. Back to fastperm2.
Nov
16
revised How to perform frequency analysis of a substitution cipher using a Base64 alphabet
Add picture, some fixes
Nov
15
revised Why we can't implement AES 512 key size?
Even more critic
Nov
15
revised How to perform frequency analysis of a substitution cipher using a Base64 alphabet
Add the third method
Nov
15
revised Why we can't implement AES 512 key size?
Tone down AES-128 apreciation
Nov
15
comment Why we can't implement AES 512 key size?
I have edited the answer to tone down the appreciation of AES-128 security. Still, if we re-key AES-128 every millisecond for thirty years, that's less than $2^{40}$ keys, and odds of hitting the same key twice are less than $2^{-49}$, an acceptable risk. However, if the same known plaintext gets enciphered with every key (as in CTR mode with zero rather than random IV), odds of finding one of the key with $2^{80}$ encryptions and searches in 16TB of data are $2^{-7}$, slightly worrying.
Nov
15
revised Why we can't implement AES 512 key size?
Criticize the "paper"
Nov
14
comment Why we can't implement AES 512 key size?
The paper that you found is vacuous to the point of being funny. The reference to an "ISO 3297:2007 Certified Organization" should act as a snake-oil warning, for this standard only defines the numbering of publications.
Nov
14
revised How to perform frequency analysis of a substitution cipher using a Base64 alphabet
Clarify the plan; automation
Nov
14
answered Why we can't implement AES 512 key size?
Nov
14
answered Key derivation for AES-Encryption key and HMAC
Nov
14
revised How to perform frequency analysis of a substitution cipher using a Base64 alphabet
There are more guesses possible for R?NF?R
Nov
14
revised How to perform frequency analysis of a substitution cipher using a Base64 alphabet
Remove pedantic and wrong use of surjective
Nov
14
revised How to perform frequency analysis of a substitution cipher using a Base64 alphabet
added 5 characters in body
Nov
14
answered How to perform frequency analysis of a substitution cipher using a Base64 alphabet
Nov
14
revised Small Prime Difference in RSA
Explain against which variant of trial division we compare Fermat
Nov
14
comment How can CBC-MAC be secure when message length is fixed?
The title of the question looks wrong to me; nearest logical substitute: How can CBC-MAC be secure only when message length is fixed?