Abstract

In cryptography, correlation attacks are a class of known plaintext attacks for breaking stream ciphers whose keystream is generated by combining the output of several linear feedback shift registers (called LFSRs for the rest of this article) using a Boolean function. Correlation attacks exploit a statistical weakness that arises from a poor choice of the Boolean function – it is possible to select a function which avoids correlation attacks, so this type of cipher is not inherently insecure. It is simply essential to consider susceptibility to correlation attacks when designing stream ciphers of this type.