签密方案的密文滥用性分析

Resistance to Misuse Ciphertext of Signcryption Scheme

对签密密文的滥用是指恶意的接收者利用收到的密文伪造新的密文,使之具有不同的接收者,现有EUF-CMA(Existential UnForgeability against adaptive Chosen Messages Attack)模型不能有效模拟签密方案的密文滥用性,一些签密方案也不能抵抗对密文的滥用攻击。该文通过对EUF-CMA模型中敌手的能力进行增强,实现了模拟签密密文滥用攻击。以新近提出的几种异构签密方案为例,描述方案中存在的针对签密密文滥用的攻击实例,分析形成攻击的原因,并提出相应的改进方法。最后,以其中一种改进方案作为实例,演示采用增强的EUF-CMA模型分析签密方案密文滥用性的过程,表明该文中针对EUF-CMA模型的增强,以及对签密方案的改进方法是合理和有效的。

The misuse of signcryption ciphertext means that the malicious recipient uses the received signcryption ciphertext to forge a new ciphertext that has a different recipient.It is found that the Existential UnForgeability against adaptive Chosen Message Attack(EUF-CMA)model can not simulate misuse attacks on signcryption schemes,and many of the existing signcryption schemes,claimed provable secure,can not resist the misuse attack.By enhancing the capabilities of adversaries in the EUF-CMA model,an extended EUFCMA model is defined which captures the security associated with the resistance to misuse attacks on signcryption schemes.This paper describes the misuse attack instances in several newly proposed heterogeneous signcryption schemes,analyzes the reasons for the attacks and proposes improvement approaches.Finally,using the enhanced EUF-CMA model,the unforgeability of an improved heterogeneous signcryption scheme is analyzed,and the procedure of simulating the misuse attack is demonstrated.The results indicate that the enhanced EUF-CMA model and the improvement approaches for signcryption schemes are reasonable and effective.