How to Enhance the Security of Public-Key Encryption at Minimum Cost
This paper presents a simple and efficient conversion from a semantically secure public-key encryption scheme against passive adversaries to a non-malleable (or semantically secure) public-key encryption scheme against adaptive chosenciphertext attacks (active adversaries) in the random oracle model. Since our conversion requires only one random (hash) function operation, the converted scheme is almost as efficient as the original one, when the random function is replaced by a practical hash function such as SHA-1 and MD5. We also give a concrete analysis of the reduction for proving its security, and show that our security reduction is (almost) optimally efficient. Finally this paper gives some practical examples of applying this conversion to some practical and semantically secure encryption schemes such as the ElGamal, Blum-Goldwasser and Okamoto-Uchiyama schemes [4,7,9].
KeywordsEncryption Scheme Random Oracle Random Oracle Model Challenge Ciphertext Decryption Oracle
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