中文摘要：

提出了一个基于身份的无密钥托管的变色龙hash函数．它在保持基于身份的变色龙hash函数的原有性质的同时，解决了基于身份体制中固有的密钥托管问题：即在该方案中，私钥产生中心（PKG）无法计算变色龙hash函数的碰撞．在此基础上，进一步使用基于身份的无密钥托管的加密方案和签名方案，实现了基于身份的无密钥托管的变色龙签名，保证了PKG无法伪造对应的变色龙签名．最后，证明了该方案满足抗碰撞性、语义安全性、消息隐藏特性和无密钥托管性．

英文摘要：

An identity-based chameleon hash function without the key escrow problem is proposed. It not only achieves all the desired security properties of the traditional identity-based chameleon hashing but also removes the inherent escrow problem of identity-based systems. That is, the private key generator （PKG） can not find a collision of our proposed identity-based chameleon hash function. Moreover, an identity-based chameleon signature without the key escrow problem is given by adoption of the identity-based encryption and the identitybased signature without the key escrow. Besides, a security proof of the proposed chameleon hashing and signature scheme is given, showing that these schemes without the key escrow are collision resistance, semantically securand message hiding.