完善保密密码体制的条件与设计

On the condition and design of perfect secrecy cryptosystem

讨论了密码体制的完善保密性,在深入分析明文、密文及密钥的概率之间的关系的基础上,给出了一般密码体制具有完善保密性的充要条件和一个性质;利用组合论的知识讨论了完善保密密码体制的设计,得到了完善保密密码体制的一个递归设计法,并给出了一类特殊完善保密密码体制的计数方面的一个结果;最后就一类特殊完善保密密码体制的存在性提出了一个问题,并做了初步分析。

Perfect secrecy of cryptosystem was discussed. Based on careful analysis of the relationship between probability of place text, cipher text and secret key, a property and a necessary and sufficient condition for perfect secrecy of general cryptosystem were presented; by using the knowledge of combination theory, we obtained the down boundary of a sort of perfect secrecy cryptosystem, got a method of the design of perfect secrecy cryptosystem. Last, we present a question about the existence of sort of perfect secrecy cryptosystem, and do preliminary analysis.