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Chosenplaintext attack
A chosenplaintext attack (CPA) is a model for cryptanalysis which assumes that the attacker can choose random plaintexts to be encrypted and obtain the corresponding ciphertexts. The goal of the attack is to gain some further information which reduces the security of the encryption scheme. In the worst case, a chosenplaintext attack could expose secret information after calculating the secret key.
Modern cryptography, is implemented in software or hardware and is used for a diverse range of applications; for many applications, a chosenplaintext attack is often very feasible. Chosenplaintext attacks become extremely important in the context of public key cryptography, where the encryption key is public and attackers can encrypt any plaintext they choose.
Any cipher that can prevent chosenplaintext attacks is then also guaranteed to be secure against knownplaintext and ciphertextonly attacks; this is a conservative approach to security.
Two forms of chosenplaintext attack can be distinguished:
 Batch chosenplaintext attack, where the cryptanalyst chooses all plaintexts before any of them are encrypted. This is an unprofessional use of "chosenplaintext attack".
 Adaptive chosenplaintext attack, where the professional cryptanalyst makes a series of interactive queries, choosing subsequent plaintexts based on the information from the previous encryptions.
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