o Symmetric Cipher Model Secret key shared by Secret key shared by sender and recipient sender and recipient Transmitted ciphertext Plaintext Plaintext Encrvption algorithm Decryption algorithm Input output (e.g, DES) (reverse of encryption algorithm) 復大辱软件学院 LiST
LiJT 11 Symmetric Cipher Model
Definition A cryptosystem is a 5-tuple(E, D,p, K, c) where p is the set of plaintexts, K the set of keys, C is the set of cipher texts E:M×K→ C is the set of Encryption algorithms, D:C×K→ M is the set of Decryption algorithms 12 復大辱软件学院 LiST
LiJT 12 Definition • A cryptosystem is a 5-tuple (E, D, p, K, C), where – p is the set of plaintexts, – K the set of keys, – C is the set of cipher texts, – E: M×K®C is the set of Encryption algorithms, – D: C×K®M is the set of Decryption algorithms