In order to resist such attack, we introduce the gray code and obtain a new mode CBC~+ which is security against adaptive adversary.

• 为了提高其安全性，在其输入中引入了随机的成分，削弱了分组密码输入输出的内在联系，构造了CBC~+模式，新模式在适应性攻击模型下，是可证明安全的。