Encryption apparatus, decryption apparatus, encryption method, decryption method, and encryption/decryption system

Abstract

In order to protect SSL encrypted communication from MITM attacks, a server certificate is used in the communication. However, operation of the server certificate is not simple, and the certificate is not sufficient to protect the communication from the MITM attacks. In SSL encrypted communication in which a password is shared between a client and a server, the client encrypts random number data and a password by means of a public key, determines a value by processing encrypted data by means of encrypted password data, and transfers the thus-determined value to the server. The server eliminates the password encrypted data from the value and back calculates the random number data, which are then decrypted, to thus acquire the random number data generated by the client. A hash value of the random number data is submitted to the client.