中文摘要：

三方口令认证密钥交换协议允许两个分别与服务器共享不同口令的用户在服务器的协助下建立共享的会话密钥,从而实现了用户间端到端的安全通信.现阶段,多数的三方口令认证密钥交换协议都是在随机预言模型下可证明安全的.但在实际应用中,利用哈希函数对随机预言函数进行实例化的时候会给随机预言模型下可证明安全的协议带来安全隐患,甚至将导致协议不安全.以基于El Gamal加密的平滑投射哈希函数为工具,在共同参考串模型下设计了一种高效的三方口令认证密钥交换协议,并且在标准模型下基于DDH假设证明了协议的安全性.与已有的同类协议相比,该协议在同等的安全假设下具有更高的计算效率和通信效率,因此更适用于大规模的端到端通信环境.

英文摘要：

Three-party password authenticated key exchange （3PAKE） protocols allow two clients to establish a common session key via the help of an authentication server. Each client only needs to share a password with the server. The derived session key can be later used to achieve end-to-end secure communications. Most of the existing 3PAKE protocols are proven secure in the random oracle model.However, these protocols may turn out to be insecure in real applications when the random oracle function is instantiated with a concrete hash function. In this paper, an efficient 3PAKE protocol is proposed using smooth projective hash function based on ElGamal public key eneryption. The security of the proposed protocol is conducted in the standard model under the DDH assumption. Compared with other related protocols, this protocol is quite efficient in terms of computation and communication costs under the same security assumption, and as a result, it is more suitable for large-scale end-to-end communication environments.