Emura 等提出的基于身份标识的代理重加密（ Emura-IB-PRE ）方案具有源隐藏特性，且在随机喻示模型下具有抗选择密文攻击安全性 . 文中提出了一种攻破 Emura-IB-PRE方案的选择密文安全性方法，证明了 Emura-IB-PRE 不能抵抗选择密文攻击，进而提出了改进的 E-SH-IB-PRE 方案，并进行了相关安全性证明 . 结果表明，文中提出的方案在随机喻示模型下具有抗选择密文攻击安全性和源隐藏特性，一级密文可公开验证的原则对代理重加密方案的设计具有重要的作用 .

As Emura-IB-PRE ， an identity label-based proxy re-encryption scheme proposed by Emura et al. ， is of source hiding property and chosen ciphertext security in random oracle model ， a chosen ciphertext security method to attack Emura-IB-PRE scheme is proposed ， and Emura-IB-PRE is proved invalid in resisting the chosen ciphertext attack. In order to solve this problem ， an improved scheme named E-SH-IB-PRE is presented and the corresponding security proof is given. The results indicate the presented scheme is secure against chosen ciphertext attack with source hiding property in random oracle model ， and that the principle ， i.e. ， the first level ciphertext can be publicly verified by proxy ， is important for proxy re-encryption schemes.