As a basic mode of operation, CBC was proved that it is secure under the standard attack model, but it is not secure under the adaptive attack model.

• 密码分组链接模式(CBC)在非适应性攻击模型下是可证明安全的，但在适应性攻击模型下却是不安全的，攻击者只需要很少的几次询问即可破坏其安全性。