Tag Info

New answers tagged

0

Your design seems to be a byte-wise generalization of Jennings' multiplexed generator rather than the alternating step generator. S. M. Jennings, “Multiplexed Sequences: Some Properties of the Minimum Polynomial,” Lecture Notes in Computer Science, vol. 149, 1983. I believe designs like hers [may even be byte based for efficiency] have been used in ...


1

The goal of an ideal cryptographically secure pseudo-random number generator (CSPRNG) is to produce a stream of numbers that no machine can distinguish from a truly random stream of numbers. Formally, it's impossible to give a proof that a CSPRNG is truly random. That being said, there exists a family of statistical tests that can measure whether a sequence ...


10

Expanding then shrinking in SHA-1 refers to the process, performed for each round (each 512-bit block of padded message), of message expansion from 512 bits to 2560 bits; keeping only 160 bits of state for the next round. The later directly follows from the construction of SHA-1 as a Merkle-Damgård hash of 160 bit. The former occurs because SHA-1's ...


2

For a fixed key, a (block) cipher is a reversible transformation of a plaintext set to ciphertext set. Usually (and in the slide) these sets are identical, and consist of all the exactly $n$-bit strings. This set has $2^n$ elements, and is often noted $\{0,1\}^n$. Note: in this notation $\{0,1\}$ designates the set with the two elements $0$ and $1$, and as ...


1

I just found a quote from our big friend Bruce Schneier in [A self-study course in block-cipher cryptanalysis][2] Chapter 2 "What does it mean to "break" a cipher". Breaking a cipher simply means finding a weakness in the cipher that can be exploited with a complexity less than brute-force. I also found this a [comment][3] in an article [AES crypto ...


2

Block ciphers map bit strings of fixed length to other bit strings of the same length. Hence, using only the block cipher primitive, you can't encrypt more than one block (typically 16 bytes), which is of course undesirable. The straight-forward (but bad!) way around this limitation would be to split up the message into chunks of block length and ...


4

Your explanation is "broken in the academically sense" - there is a theoretical way to break the algorithm better than brute force. AES is broken in this way. There's also "broken in the practical sense", which means you can break an cipher in real applications or protocols. AES is still save in this sense, because you still need too much compution power and ...


2

In general, a cipher is broken if it is possible to win the following game. The game has two players, the challenger and the defender. The challenger selects a pair of messages, $m_0$ and $m_1$. The defender selects an encryption key, $k$, and encrypts either $m_0$ or $m_1$. He then sends the resultant cipher text for his chosen message to the challenger. ...


2

In 2013, I visited the National Cryptologic Museum and researched/photographed the donated materials on the Chaocipher from the Byrne family. As it pertains to your question regarding the security of the cipher, it is true that while the original algorithm has been now been known for several years, to date no known cipher-text only decryption has yet been ...


2

Work factor is a more appropriate description because time factor is relative to processing power. Time factor, time complexity, computational complexity, and work factor, are used to describe the same thing. When someone says time complexity, they are probably not talking about actual time, but rather computation. Work factor would be something like "200 ...



Top 50 recent answers are included