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 8/342022/10/9 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