4 Cryptographic Protocols
4.1 Cryptographic Protocols
Up to this point, we have primarily considered encryption systems, that is, methods to encrypt and decrypt secret messages. Recall that cryptosystems can be classified as symmetric key or public (asymmetric) key. In the former, both the encoding and decoding algorithms are supposedly known only to the sender and receiver, while in the latter, the encryption method is public knowledge, but only the receiver knows how to decode.
Secure confidential message transmission is only one type of task that must be done with secrecy and there are many other tasks and procedures that are important in cryptography. What is meant by a cryptographic task will be made a bit more precise via specific examples ...