Burrows-Abadi-Needham logic

Burrows-Abadi-Needham logic (also known as the BAN logic) is a set of rules for defining and analyzing information exchange protocols. Specifically, BAN logic helps its users determine whether exchanged information is trustworthy, secured against eavesdropping, or both. BAN logic starts with the assumption that all information exchanges happen on mediums vulnerable to tampering and public monitoring. This has evolved into the popular security mantra, "Don't trust the network."
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