Score:1

Does CCA security imply perfect secrecy?

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Can any encryption scheme that is CCA (Chosen Ciphertext Attack) secure be considered to achieve perfect secrecy?

Score:7
us flag

Perfect secrecy & [the traditional/standard definition of] CCA security are incompatible.

Shannon's theorem says that if you want perfect secrecy, then the key needs to be longer than the total length of all plaintexts encrypted under that key. But in the CCA game there is a single key, and no a-priori limit to the total number of encryptions (and hence total plaintext length) that an attacker can request under that key.

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