Chosen Ciphertext Attack

Related Concepts

Block Ciphers; Public Key Cryptography; Symmetric Cryptosystem

Definition

Chosen ciphertext attack is a scenario in which the attacker has the ability to choose ciphertexts C _i and to view their corresponding decryptions – plaintexts P _i . It is essentially the same scenario as a chosen plaintext attack but applied to a decryption function, instead of the encryption function. The attack is considered to be less practical in real-life situations than chosen plaintext attacks. However, there is no direct correspondence between complexities of chosen plaintext and chosen ciphertext attacks. A cipher may be vulnerable to one attack but not to the other attack or the other way around. Chosen ciphertext attack is a very important scenario in public key cryptography, where known plaintext and even chosen plaintext scenarios are always available to the attacker due to publicly known encryption key. For example, the RSA public-key encryption system is not secure against adaptive...