Stream/block ciphers, difference equations and algebraic attacks

Algebraic Attacks on Stream Ciphers (survey)

Most stream ciphers based on linear feedback shift registers (LFSR) are vulnerable to recent algebraic attacks. In this survey paper, we describe generic attacks: existence of algebraic equations and fast algebraic attacks. The generic attacks only states the existence and gives the upper bound of the complexity. Thus we should find good algebraic equations, case by case, in order to apply the ...

Algebraic attacks on certain stream ciphers

To encrypt data streams of arbitrary lengths, keystream generators are used in modern cryptography which transform a secret initial value, called the key, into a long sequence of seemingly random bits. Many designs are based on linear feedback shift registers (LFSRs), which can be constructed in such a way that the output stream has optimal statistical and periodical properties and which can be...

Algebraic Attacks on Clock-Controlled Stream Ciphers

Stream ciphers are encryption algorithms used for ensuring the privacy of digital telecommunications. They have been widely used for encrypting military communications, satellite communications, pay TV encryption and for voice encryption of both fixed lined and wireless networks. The current multi year European project eSTREAM, which aims to select stream ciphers suitable for widespread adoptat...

Algebraic Difference Equations

CTC2 and Fast Algebraic Attacks on Block Ciphers Revisited

The cipher CTC (Courtois Toy Cipher) described in [4] has been designed to demonstrate that it is possible to break on a PC a block cipher with good diffusion and very small number of known (or chosen) plaintexts. It has however never been designed to withstand all known attacks on block ciphers and Dunkelman and Keller have shown [13] that a few bits of the key can be recovered by Linear Crypt...