Message syntax (cryptography)

Messages

• Names: $A,B$ or Alice, Bob, etc
• Keys: $K$ and inverse keys $K^{-1}$
  • Encryption $\{M{\}}_K$, e.g. encryption with $A$‘s public key: $\{M{\}}_{K_A}$
  • Signing $\{M{\}}_K^{-1}$, e.g. signing with $A$‘s public key: $\{M{\}}_{K_A^{-1}}$
  • Symmetric keys $\{M{\}}_{K_{AB}}$
• Nonces: $NA,N1,\dots$ Fresh data items used for challenge / response.
• Timestamps: $T$ Denote time, e.g. used for key expiration.
• Message concatenation: $M_1,M_2$

Example of a message: $\{A,T_1,K_{AB}{\}}_{K_B}$