Structural Cryptanalysis

Definition

Structural Cryptanalysis is a branch of Cryptanalysis which studies the security of cryptosystems described by generic block diagrams. It analyzes the syntactic interaction between the various blocks, but ignores their semantic definition as particular functions. Typical examples include meet-in-the-middle attacks on multiple encryptions, the study of various chaining structures used in modes of operation, and the properties of Feistel structures or substitution–permutation networks with a small number of rounds.

Theory and Application

Structural attacks are often weaker than actual attacks on given cryptosystems, since they cannot exploit particular weaknesses (such as bad differential properties or weak avalanche effect) of concrete functions. The positive side of this is that they are applicable to large classes of cryptosystems, including those in which some of the internal functions are unknown or key dependent. Structural attacks often lead to deeper theoretical...