key
- Secret key(密钥）：ues the same key to Encryption and decryption（symmetric-key）对称加密，需要绝对安全的空间来传递key
- Pulic kay(公钥）：ues different key to Encryption and decryption （asymmetric-key)非对称加密
Caeser Cipher(凯撒密码）
- core：replace（替换思想）
Cryptographic Hash（又是可爱的哈希）
- Converting any length of input into a fixed length string or digest of information（任意长度输入转化为固定长度二进制串）
- 哈希碰撞：Different inputs give the same result
- a good hash function:any tiny change --> a big change with digest
Hash for Password(使用哈希的密码系统）
- Do not store the password you entered directly（非直接存密码)
- store digest(存储哈希值）
- 几乎是不可逆
- share secret（共享密码）
在信息后面加上特定字符串，再哈希
Public Key Encryption Confidentiality
- base on two prime(从两个素数开始）
- Public key:Open to the outside world for encryption(公钥）
- Private key: Used for decryption, private ownership（私钥）
- not perfect but it is hard to break
- Public keys can be distributed arbitrarily without protection(公钥分发简单）
- private keys are protected in computers or servers.
SSL(Secure Sockets Layer)安全套接字层
- Security for TCP
- Located between Application Layer and Transport Layer
- Because of the hierarchical structure, the underlying structure only needs to be responsible for the transmission of ciphertext (it is not known whether the transmission is ciphertext or plaintext).
TLS(Transpot Layer Security)
Digital Certificates（数字证书）
- Make sure the person you are talking to（确保谈话对象）
- Amazon发公钥给VerSign,VerSign计算验证后，确实是Amazon,就返回一个带签名的公钥
Summary
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