Improved convertible authenticated encryption scheme with provable security |
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Authors: | Han-Yu Lin Shih-Kun Huang |
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Affiliation: | a Department of Information Management, Chang Gung University, Tao-Yuan, 333, Taiwan b Taiwan Information Security Center at NTUST (TWISC@NTUST), Taipei, 106, Taiwan c Department of Computer Science, National Chiao Tung University, Hsinchu, 300, Taiwan |
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Abstract: | Convertible authenticated encryption (CAE) schemes allow a signer to produce an authenticated ciphertext such that only a designated recipient can decrypt it and verify the recovered signature. The conversion property further enables the designated recipient to reveal an ordinary signature for dealing with a later dispute over repudiation. Based on the ElGamal cryptosystem, in 2009, Lee et al. proposed a CAE scheme with only heuristic security analyses. In this paper, we will demonstrate that their scheme is vulnerable to the chosen-plaintext attack and then further propose an improved variant. Additionally, in the random oracle model, we prove that the improved scheme achieves confidentiality against indistinguishability under adaptive chosen-ciphertext attacks (IND-CCA2) and unforgeability against existential forgery under adaptive chosen-message attacks (EF-CMA). |
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Keywords: | Cryptography Convertible Authenticated encryption ElGamal system Provable security Random oracle model |
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