一种逼近完善保密的可证明安全随机分组密码

Provably-Secure Randomized Block Cipher Approaching to Perfect Secrecy

当前广泛使用的迭代型分组密码一般为固定变换,不利于安全性.“一次一密”乱码本方案具有完善保密性,但不具有实用性.为兼顾随机性和实用性,本文提出一种基于短密钥的逼近完善保密的实用化随机分组密码(简称BREA方案),主要思想是:预置一个固定规模的可公开共享的随机数据库,每次分组加密从外部引入真随机数因子用于随机数据库元素随机查取与合成运算,用其输出对消息分组进行掩盖从而实现按分组一次一密随机加密.BREA方案在任意位置观察序列和一致性检验攻击模型下,对任意长度的消息进行加密,具有安全性可度量的高概率逼近“一次一密”完善保密性.

At present,the widely used iterative block ciphers are generally fixed transformations,which are not conducive to security.The scheme of“one-time pad”provides perfect confidentiality,however,it is not practical.In order to compromise between randomness and practicability,this paper proposes a practical random block cipher(BREA scheme for short)based on short keys,which is close to perfect confidentiality.The main idea is as follows:preset a fixed-scale publicly shared random database,then introduce the true random number factor from the outside for random query and synthesis of random database elements every time the block is encrypted,and its output is used to mask the message packet so as to realize random encryption according to the block which is“one-time one encryption”.BREA scheme encrypts messages of arbitrarily length under the observation sequence at any position and the consistency test attack model,which has a high probability of measurable security and is close to the perfect confidentiality of“one-time one encryption”.