Protocol Composition Logic is a formal method that can be used for proving security properties of cryptographic protocols that use symmetric-key and public-key cryptography.
PCL is designed around a process calculus with actions for various possible protocol steps (e.g. generating random numbers, performing encryption, decryption and digital signature operations as well as sending and receiving messages).
[1] Some problems with the logic have been found, implying that some currently claimed results cannot be proven within the logic.
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