4/ Cryptography has three general classes:
-Hash functions—turning data into a unique fixed-length string, akin to a fingerprint
-Symmetric cryptography—encrypted communication w/ a shared secret key
-Asymmetric cryptography—encrypted communication via public/private key pairs https://t.co/8PZ5pHHyvU
4/密码学有三大类：
-散列函数将数据转换为唯一的固定长度字符串，类似于指纹
-使用共享密钥的对称加密通信
-非对称加密通过公钥/私钥对加密通信https://t.co/8PZ5pHHyvU