The paper discusses the use of encryption for achieving authenticated communication in computer networks, focusing on protocols for establishing authenticated connections, managing authenticated mail, and ensuring signature verification and document integrity. Both conventional and public-key encryption algorithms are considered. The authors present detailed protocols for these purposes, highlighting the differences between conventional and public-key encryption in terms of key usage and the role of authentication servers. They also address the implementation of authentication servers and the handling of one-way communication in mail systems. The paper concludes by comparing the similarities and differences between protocols using conventional and public-key encryption, emphasizing the importance of caching and the need for secure implementation. The authors suggest that the choice of encryption technique should be based on the economic and cryptographic strength of the algorithms rather than their impact on protocol complexity.The paper discusses the use of encryption for achieving authenticated communication in computer networks, focusing on protocols for establishing authenticated connections, managing authenticated mail, and ensuring signature verification and document integrity. Both conventional and public-key encryption algorithms are considered. The authors present detailed protocols for these purposes, highlighting the differences between conventional and public-key encryption in terms of key usage and the role of authentication servers. They also address the implementation of authentication servers and the handling of one-way communication in mail systems. The paper concludes by comparing the similarities and differences between protocols using conventional and public-key encryption, emphasizing the importance of caching and the need for secure implementation. The authors suggest that the choice of encryption technique should be based on the economic and cryptographic strength of the algorithms rather than their impact on protocol complexity.