Chosen Plaintext Attack

Related Concepts

Block Ciphers; Digital Signature Schemes; MAC algorithms; Public Key Cryptography; Symmetric Cryptosystem

Definition

Chosen plaintext attack is a scenario in which the attacker has the ability to choose plaintexts P _i and to view their corresponding encryptions – ciphertexts C _i . This attack is considered to be less practical than the known plaintext attack, but is still a very dangerous attack. If the cipher is vulnerable to a known plaintext attack, it is automatically vulnerable to a chosen plaintext attack as well, but not necessarily the opposite. In modern cryptography, differential cryptanalysis is a typical example of a chosen plaintext attack. It is also a rare technique for which conversion from chosen plaintext to known plaintext is possible (due to its work with pairs of texts).

Theory

If a chosen plaintext differential attack uses m pairs of texts for an n bit block cipher, then it can be converted to a known-plaintext attack which will require \({2}^{n/2}\sqrt{2m}\)...