Cryptology ePrint Archive: Report 2008/330

Chosen ciphertext secure public key encryption under DDH assumption with short ciphertext

Xianhui Lu, Xuejia Lai, Dake He

Abstract: An efficient variant of the ElGamal public key encryption scheme is proposed which is provably secure against adaptive chosen ciphertext attacks(IND-CCA2) under the decisional Diffie-Hellman(DDH) assumption. Compared to the previously most efficient scheme under DDH assumption by Kurosawa and Desmedt [Crypto 2004] it has one group element shorter ciphertexts, 50\% shorter secret keys, 25\% shorter public keys and it is 28.6\% more efficient in terms of encryption speed, 33.3\% more efficient in terms of decryption speed. A new security proof logic is used, which shows directly that the decryption oracle will not help the adversary in the IND-CCA2 game. Compared to the previous security proof, the decryption simulation is not needed in the new logic. This makes the security proof simple and easy to understand.

Category / Keywords: public key encryption, IND-CCA2, DDH

Date: received 31 Jul 2008, last revised 3 Aug 2008, withdrawn 23 Oct 2009

Contact author: luxianhui at gmail com

Available format(s): (-- withdrawn --)

Version: 20091023:135418 (All versions of this report)

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