A method for verifying content data to be used in a vehicle is provided. The method includes acquiring content data, acquiring, from partial data divided from the content data, a respective plurality of first hash values, acquiring a signature generated by using the first hash values and a key, acquiring state information that indicates a state of a vehicle, determining an integer N that is greater than or equal to one based on the acquired state information, generating, from N pieces of partial data included in the partial data, respective second hash values, verifying the content data by using each of (a) a subset of the plurality of first hash values respectively generated from partial data other than the N pieces of partial data, (b) the second hash values, and (c) the signature, and outputting information that indicates a result of the verifying.