Tightly Secure Public Key Encryption With Equality Test in Setting With Adaptive Corruptions

Abstract

Public Key Encryption with Equality Test (PKEET) is a cryptographic primitive that allows an authorized entity to test whether two given ciphertexts are the encryption of the same message without decrypting them. The security of cryptographic schemes is analyzed using security model, and thus in order to derive reasonable security against the real attackers, the security model should reflect the real attack as closely as possible. However, security model widely used by PKEET fails to capture corruption attack, since it does not cover the real attacker who can adaptively corrupt users. On the other hand, many PKEET schemes suffer from a security loss that is linear in the number of users when using security model with adaptive corruption attack, which causes that the actual security guarantees of the schemes linearly degrade in that. Therefore, the goal of this paper is to resolve these two problems. We present a PKEET scheme in setting with adaptive corruptions in which the security loss is a constant, and in particular, the comparison shows that our scheme is efficient.

Keywords

• Multi-user setting
• adaptive corruptions
• tight reduction
• public key encryption
• equality test