This chapter demonstrates how logic programming, particularly using linear logic, can be used to encode and reason about simple security protocols. It discusses specifying communication processes and protocols, including communication on a public network, static key distribution, and dynamic symbol creation. The chapter explores how to represent encrypted data as an abstract data type and model protocols as theories in linear logic. It also covers techniques for abstracting the internal states of agents and representing agents as nested implications. Bibliographic notes cite relevant work on formal methods for security protocol analysis.