Lecture_7

Principles of Public-Key Cryptosystems
Symmetric algorithms used same secret key for encryption and decryption
Asymmetric algorithms in public-key cryptography use one key for encryption and different but related key for decryption
Characteristics of asymmetric algorithms:
Require: Computationally infeasible to determine decryption key given only algorithm and encryption key
Optional: Either of two related keys can be used for encryption, with other used for decryption

Public and Private Keys
Public-Private Key Pair
User A has pair of related keys, public and private: (PUA, PRA); similar for other users
Public Key
Public, Available to anyone
For secrecy: used in encryption
For authentication: used in decryption
Private Key
Secret, known only by owner
For secrecy: used in decryption
For authentication: used in encryption
Confidentiality with Public Key Crypto
Encrypt using receivers public key
Decrypt using receivers private key
Only the person with private key can successful decrypt