https://textbook.cs161.org/crypto/目的:Confidentiality 保密性 严格定义:IND-CPA (Indistinguishability under chosen-plaintext attack) 选择明文攻击下的不可区分性Integrity and Authentication 完整性,无篡改常用加密算法:对称加密算法哈希函数MAC (Message Authentication Codes) 消息验证码公钥加密算法数字签名HashKDFPBKDFRandom Byte Generator