A code stream and data indicating a normalization method are inputted to a normalization processing unit 21, and the normalization processing unit applies normalization processing to the code stream to generate a normalized code stream. Next, when signature data is inputted, a verification processing unit 22 performs encryption and decryption processing with respect to the signature data using a public key Kp and calculates a Hash value (first Hash value) and, on the other hand, calculates a Hash value of the normalized code stream (second Hash value). Next, the verification processing unit compares the first Hash value and the second Hash value and, if the first Hash value and the second Hash value are equal, judges that the code stream is not falsified. On the other hand, if the first Hash value and the second Hash value are not equal, the verification processing unit judges that the code stream is falsified.