To provide an e-mail transmission and reception system which realizes the secure transmission and reception of a telegraphic message and the reliable authentication of an opposite party also on the Internet where the telegraphic message is easy to tap or alter.

This telegraphic message transmission and reception system is provided with a client and common key generation means for hash-converting an inputted authentication password for generating a common key, a client/MD generation means for hash-converting the contents of an inputted request plaintext for generating a message digest, and a client/telegraphic message ciphering means which obtains the generated common key and the message digest, attaches the message digest to the request plaintext and ciphers it by using the common key to generate a request cipher sentence.