OFBNLF加密工作模式的分析

Analysis of the OFBNLF encryption mode of operation

OFBNLF(output feedback with a nonlinear function)模式是我国分组密码工作模式的国家标准之一,选择明文攻击不可区分(IND-CPA)模型则是用来评判分组密码工作模式的重要安全指标.迄今为止,还没有文献对OFBNLF模式的安全性进行分析或证明,也没有文献对其软件实现进行评估.本文对OFBNLF模式的安全性分析进行了研究,在给出OFBNLF模式的在线加密描述的基础上,采用做游戏(game-playing)的技术,第一次证明了OFBNLF模式在逐分组选择明文攻击不可区分(BWIND-CPA)模型下的安全性.鉴于之前对BW-IND-CPA模型的形式定义并没有对一般的加密模式进行在线的形式化处理,本文在给出在线加密形式定义的基础上,重新对BW-IND-CPA模型进行了定义.同时还对OFBNLF软件实现效率做了评估,并与国家标准中其他的加密模式在安全性和软件实现效率方面分别进行了对比.

OFBNLF is one of the national standardized block cipher modes of operation. In this mode, indistinguishability under chosen plaintext attack is an important security index. To the best of our knowledge, to date no analysis of the security and software implementation efficiency of OFBNLF mode has been conducted. In this paper, we analyze the security of OFBNLF and show that OFBNLF is blockwise-IND-CPA（indistinguishability under blockwise-based chosen plaintext attack） using game-playing techniques based on the description of online encryption on OFBNLF. The previous definition of BW-IND-CPA mode was not based on online mode; however, in this paper, we redefine BW-IND-CPA mode on the basis of online encryption. In addition, we compare OFBNLF mode with other encryption modes of the national standard in terms of security and software implementation efficiency.