An information processing method enables verification of validity of signed data using received partial signed data parts, even when all the signed data is not received. According to the information processing method, signature data including a signature value and digests of a plurality of partial signed data parts is received. Then, the signature data is verified by using the signature value and the digests of a plurality of partial signed data parts. Subsequently, the partial signed data is received according to a result of verifying the signature data. Then, the partial signed data is verified using the partial signed data and the digest of the partial signed data.