Cryptography

11 Introduction to Cryptanalysis Attacks on Symmetric Ciphers

Cryptanalysis is the science and techniques of analyzing and breaking cryptographic algorithms and protocols. There exist hundreds of cryptanalysis attack variants. Cryptanalysis is a very exciting field; and improvements of existing attacks are proposed every year. Cryptanalysis attacks can be categorized according to various criteria, such as:

• Nongeneric vs generic attacks: in the first category, attackers take advantage of vulnerabilities of internal components of attacked ciphers, while they do not in the second category. In general, nongeneric attacks are more efficient than generic ones, as attackers know the internal vulnerabilities of attacked ciphers.
• Statistical vs deterministic attacks: in the first category, the attackers derive some properties of attacked ciphers that can hold with some probabilities and exploit such statistical knowledge to partially or entirely recover keys. In the second category, attackers design models of ciphers in form of equations. Models are used to reduce the search space of keys. Linear and differential cryptanalyses are examples of statistical attacks, while algebraic attacks are deterministic. Linear cryptanalysis together with differential cryptanalysis are the most widely used attacks against block ciphers.
• Known vs chosen information: there exist four main types (or models) of attacks: ciphertext-only, known-plaintext, chosen-plaintext, and chosen-ciphertext attacks. ...