线衣 公开密钥认证过程 1950 Alice's public key ring Joy Mike Bob Bob's private Bob's public key key Transmitted ciphertext Plaintext Plaintext input Encryption algorithm Decryption algorithm output (e.g.,RSA) (reverse of encryption algorithm) (b)Authentication Figure 9.1 Public-Key Cryptography 2022/10/9 现代密码学理论与实践-09 7134
2022/10/9 现代密码学理论与实践-09 7/34 公开密钥认证过程
常规和公开密钥加密的重要特征 Table 9.1 CONVENTIONAL AND PUBLIC-KEY ENCRYPTION Conventional Encryption Public-Key Encryption Needed to Work: Needed to Work: 1.The same algorithm with the same key is used for 1. One algorithm is used for encryption and decryption with a encryption and decryption. pair of keys,one for encryption and one for decryption. 2.The sender and receiver must share the algorithm and the 2.The sender and receiver must each have one of the matched key. pair of keys(not the same one). Needed for Security: Needed for Security: 1.The key must be kept secret. 1.One of the two keys must be kept secret. 2.It must be impossible or at least impractical to decipher a 2.It must be impossible or at least impractical to decipher a message if no other information is available. message if no other information is available. 3. Knowledge of the algorithm plus samples of ciphertext must 3. Knowledge of the algorithm plus one of the keys plus be insufficient to determine the key. samples of ciphertext must be insufficient to determine the other key. 2022/10/9 现代密码学理论与实践-09 8/34
2022/10/9 现代密码学理论与实践-09 8/34 常规和公开密钥加密的重要特征
因海冷K大 公开密钥密码系统：保密性 1950 C=KUp(M) Cryptanalyst M=KRp(C) KRb Source A Destination B Message X Encryption Decryption X Destination Source Algorithm Algorithm KUb KRb Key Pair Source Figure 9.2 Public-Key Cryptosystem:Secrecy 2022/10/9 现代密码学理论与实践-09 9/34
2022/10/9 现代密码学理论与实践-09 9/34 公开密钥密码系统：保密性 C = KUb (M) M = KRb (C)
公开密钥密码系统：认证 车不 105 S=KRa(M) M=KUa(S) Cryptanalyst Source A Destination B Message Encryption Y Decryption Source Destination Algorithm Algorithm KRa KUa Key Pair Source Figure 9.3 Public-Key Cryptosystem:Authentication 甲 2022/10/9 现代密码学理论与实践-09 10/34
2022/10/9 现代密码学理论与实践-09 10/34 公开密钥密码系统：认证 S = KRa (M) M = KUa (S)
公开密钥密码系统：保密和认证 15 C=KR(KUp(M)) M=KRp(KU(C)) Source A Destination B Z Message Encryption Encryption Decryption Decryption Message Source Algorithm Algorithm Algorithm Algorithm Dest. KUb KRb Key Pair Source KRa KUa Key Pair Source Figure 9.4 Public-Key Cryptosystem:Secrecy and Authentication 2022/10/9 现代密码学理论与实践-09 11/34
2022/10/9 现代密码学理论与实践-09 11/34 公开密钥密码系统：保密和认证 C = KRa (KUb (M)) M = KRb (KUa (C))