Cryptography: communication in the presence of adversaries.
Goals:
- privacy: adversary learns nothing about message sent
- authentication: recipient of message can convince herself that the message as received originated with alleged sender.
- signatures: recipient of a message can convince a third party that the message as received originated with the alleged signer.
- minimality: nothing is communicated except that which is specifically desired to be communicated.
- simultaneous exchange: something of value not released untile something else of value received.
- multi-party coordination: parties can coordinate activities towards common goal even in presence of adversaries.