Https握手(验证证书->交换密钥): 证书防伪造(签名验证), 防篡改(签名验证), 防替换(域名验证), 防假冒(解不开密钥)
Https通信: 防窃听(对称加密), 防篡改(签名), 防重放(序列号)
Https的双向认证
服务器认证: 验证服务器证书(证书链)+验证私钥(协商密钥)
客户端认证: 验证客户端证书(证书链)+验证私钥(验证客户端签名)


To prevent message replay or modification attacks, the MAC is computed from the MAC secret, the sequence number, the message length, the message contents, and two fixed character strings.