标准模型下的灵活细粒度授权密文一致性检测方案

密文一致性检测公钥加密方案是一种检测者能够在无需解密密文的情况下检测一对密文的一致性，即该对密文解密所得明文是否一致的公钥加密方案.已有工作中提及的细粒度授权方案和灵活授权方案在授权粒度方面对密文一致性检测公钥加密方案的功能性进行了改进：细粒度授权方案允许2名用户生成专用于检测这2名用户的所有密文的一致性的令牌.灵活授权方案则将令牌的授权客体从用户级别拓展至指定密文级别.2种方案拥有各自的应用场景且在功能性方面互不包含.因此提出灵活细粒度授权密文一致性检测公钥加密方案.与已有方案相比，该方案在计算效率和参数大小方面相当,并具备适应性选择密文攻击安全性、细粒度授权安全性.该方案兼具细粒度授权特性与灵活细粒度特性.同时，对比依赖预言机模型的已有相关方案，其安全性证明基于标准模型之上.

Flexible Fine-Grained Authorization Public Key Encryption with Equality Test Under Standard Model

Public key encryption with equality test(PKEET) is a public key encryption scheme which allows testers to perform equality tests on ciphertexts without holding corresponding private keys, that is, detecting whether the plaintexts decrypted from given cyphertext are equal. The fine-grained authorization PKEET (FG-PKEET) and PKEET with flexible authorization (PKEET-FA) schemes mentioned in previous works improve the functionality of PKEET in aspect of authorization granularity: FG-PKEET scheme allows one user to interact with another user to generate a token specifically for detecting the equality of all these two users’ ciphertexts, while PKEET-FA scheme extends the type of authorization object of the token from user level to ciphertext level, permitting one user to authorize on a specific ciphertext. Both solutions have their own application scenarios and do not include each other in terms of functionality. Thus we propose flexible fine-grained authorization PKEET scheme. Our scheme obtains security properties related to adaptive ciphertext attack and fine-grained authorization. Our solution combines both fine-grained authorization and flexible fine-grained features, allowing two users to authorize respectively on one specified ciphertext or all his ciphertexts. Meanwhile, comparing to existing PKEET schemes with fine-grained authorization or flexible authorization features which rely on random oracle model, our scheme’s security properties are proved under standard model.