Data authentication device and data authentication method

A data authentication device, comprising:

• a hash value calculator to calculate a hash value of distribution information,
• a memory to store, as an authentication information history, a history of second authentication information of communication data which was received in the past from another communication device and which includes first authentication information, the distribution information, and the second authentication information, the memory storing the hash value of the distribution information calculated by the hash value calculator so as to relate the hash value to the second authentication information of the authentication information history;
• and
• an authenticator to verify, on the basis of first authentication information of new communication data being newly received communication data, authenticity of second authentication information of the new communication data and to compare a hash value of distribution information included in the new communication data and the second authentication information included therein with the authentication information history stored in the memory to verify freshness of the new communication data.

A data authentication method comprising:

• calculating a hash value of distribution information;
• storing, as an authentication information history, a history of second authentication information of communication data which was received in the past from another communication device and which includes first authentication information, the distribution information, and the second authentication information, and storing the calculated hash value of the distribution information so as to relate the hash value to the second authentication information of the authentication information history;
• and
• verifying, on the basis of first authentication information of new communication data being newly received communication data, authenticity of second authentication information of the new communication data and comparing a hash value of distribution information included in the new communication data and the second authentication information included therein with the stored authentication information history, for verifying freshness of the new communication data.