A method for providing cryptographic functions to data packets at the PPP layer of a network stack is presented. The method includes the steps of intercepting PPP datagrams having at least one encapsulated IP packet en route along the protocol stack; decapsulating the PPP datagrams to retrieve the encapsulated IP packet, determining whether to process the IP packet by modifying the IP packet to provide the cryptographic functions, and encapsulating the IP packet for transmission to a next layer of the network stack.