Encryption communication system, encryption communication method, security chip, communication apparatus, and control method and control program of communication apparatus

Abstract

This invention is directed to an encryption communication system for preventing leakage of a common key and improving the confidentiality of communication information. The encryption communication system uses a pair of a first private portion and a first public portion and a pair of a second private portion and a second public portion in a key predistribution system (KPS) The encryption communication system comprises a ciphertext generator that generates a ciphertext by generating, in a first security chip (TPM) of a first communication apparatus, a first common key by the first private portion held in the first security chip using the second public portion transmitted from a second communication apparatus as a communication partner, and encrypting a plaintext using the first common key in the first security chip, and a decryptor that generates a plaintext by generating, in a second security chip of the second communication apparatus, a second common key by the second private portion held in the second security chip using the first public portion transmitted from the first communication apparatus as a communication partner, and decrypting the ciphertext received from the first communication apparatus using the second common key in the second security chip.