针对并行可否认认证问题,在UC(universally composable)安全架中,基于WI(witness indistinguishable)提出了一种新的研究思路和解决方法.根据可否认认证的安全目标,形式化地建立了UC安全的并行可否认认证模型.利用可验证平滑投影哈希函数和非承诺加密体制,构造了一类新的并行可否认认证协议结构,基于确定性复合剩余假设和确定性Diffie-Hellman假设,实现了一个具体的协议方案在公共参考串模型中,利用UC框架解决并行协议仿真问题,与定时假设和公共目录方案相比,不需要限定攻击者能力.新方案具备前向可否认性,是自适应攻击者UC安全的、不同于CCA2加密体制结构或多陷门承诺结构的并行可否认认证,协议效率得到了改善.
A new approach and an idea for exploration are presented to the concurrent deniable authentication based on witness-indistinguishable (WI) within the framework of universally composable (UC) security. A definition of an ideal functionality for deniable authentication is formulated. A new deniable authentication protocol is proposed based on two primitives of the verifiably smooth projective Hashing (VSPH) and non-committing encryptions (NCE). This new approach is practically relevant to VSPH based on the Decisional Diffie-Hellman (DDH) assumption and NCE based on the decisional composite residuosity (DCR) assumption. Compared with a timing constraint and public directory model, simulation of the concurrent protocols is not needed to restrict an adversary capability in a common reference string (CRS) model. The protocols are forward deniable and UC security against adaptive adversaries. Unlike previous proposals with the CCA2 public-key cryptosystem or multi-trapdoor commitments paradigm, the new paradigm leads to more efficient protocols.