Electronic data is input. The electronic data is divided into N (N is an integer satisfying N≧2) segments. Examination data is generated by repeating, up to the Nth segment, the computation processing of using the computation result obtained by performing predetermined computation on the data of the Mth (M is an integer satisfying 1≦M≦N−1) segment as an input for predetermined computation of the data of the (M+1)th segment. Verification data for the electronic data is generated so as to contain, as intermediate data, the examination data and a computation result in the middle of generating the examination data.