First, some definitions,

• "encoding" uses a code-book
• "encryption" uses a procedure
• "exposure" is the basis for enforcing many protocols
  this removes the need for a trusted enforcement agent

then, some conventions and basic understandings,

• secrecy vs security
• special functions
• the cast of characters

then a survey of cryptographic technology.

• private key encryption
• public key encryption
• practical public key encryption
• digital signature
• certification of keys and other documents
• re-encryptable message
• zero-knowledge proofs
• partial keys / partial decryption