Many key-agreement and -transport protocols, usually based on the Diffie-Hellman and ElGamel public key principles, allow for an active adversary to modify the messages exchanged between a sender and receiver.

• 很多密钥协商和传输协议通常都以Diffie-Hellman和ElGamel公钥原则为基础,它们会听任活跃的入侵方修改发件人与收件人之间交换的消息。