To deal with active attacks in public key encryptions, the notion of security against an adaptive chosen ciphertext attack has been defined by Researchers. If an adversary can inject messages into a network, these messages may be ciphertexts, and the adversary may be able to extract partial information about the corresponding cleartexts through its interaction with parties in the network. The Security against chosen ciphertext attack is defined using an “decryption oracle.” Given an encryption of a message the “ciphertext” we want to guarantee that the adversary cannot obtain any partial information about the message. A method of securing Public Key Cryptosystems using hash functions is described in this chapter.
Rerandomizable and Replayable Adaptive Chosen Ciphertext Attack Secure Cryptosystems
