Cryptographic communication apparatus and cryptographic communication system

A cryptographic communication system for conducting a key exchange procedure between a first cryptographic communication apparatus and a second cryptographic communication apparatus that share a password with each other, wherein

• the first cryptographic communication apparatus includes:
• a random number generator that generates a first random number and a second random number;
• a first encryption unit that encrypts information that is based on the first random number by the aid of a public key of the second cryptographic communication apparatus;
• a second encryption unit that encrypts the information that is based on the first random number encrypted by the first encryption unit, by the aid of the password;
• a third encryption unit that encrypts information that is based on the second random number by the aid of the first random number;
• and
• a transmitter that transmits a first signal and a second signal to the second cryptographic communication apparatus, the first signal including the information that is based on the first random number encrypted by the second encryption unit, and the second signal including the information that is based on the second random number encrypted by the third encryption unit, and
• the second cryptographic communication apparatus includes:
• a receiver that receives the first signal and the second signal;
• a first decryption unit that decrypts the information that is based on the first random number encrypted by the second encryption unit by a secret key paired with the public key and the password to acquire the first random number;
• and
• a second decryption unit that calculates the second random number according to the information that is based on the second random number encrypted by the third encryption unit by the aid of the first random number acquired by the first decryption unit.