2L

callous disregard of his responsibility

[perfect] forward secrecy
a property of secure communication protocols in which compromise of long-term keys does not compromise past session keys.
1、私钥的泄漏【不会导致】以前产生的会话密钥的泄漏
2、如果有这个性质，那么协议存在私钥泄漏的时候，可以【保护过去】的会话内容