Cryptology ePrint Archive: Report 2007/388

On Ciphertext Undetectability

Peter Gazi and Martin Stanek

Abstract: We propose a novel security notion for public-key encryption schemes -- ciphertext undetectability. Informally, an encryption scheme has the property of ciphertext undetectability, if the attacker is unable to distinguish between valid and invalid ciphertexts. We compare this notion with the established ones, such as indistinguishability of ciphertexts and plaintext awareness. We analyze the possibilities of constructing schemes with the property of ciphertext undetectability. Moreover, we prove that the Damgard ElGamal, the Cramer-Shoup scheme and its lite variant achieve ciphertext undetectability under standard assumptions.

Category / Keywords: public-key cryptography / ciphertext undetectability

Date: received 2 Oct 2007, last revised 19 Nov 2007

Contact author: gazi at dcs fmph uniba sk

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Version: 20071119:165351 (All versions of this report)

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