A non-transitory computer readable medium storing a program causing a computer to execute a process including: accepting an instruction for verifying an electronic signature added to information; verifying the electronic signature on the basis of an electronic certification corresponding to the electronic signature in accordance with the accepted instruction; calculating, when it is determined that the information has not been tampered with, a hash value of a combination of the information, the electronic signature, and validity-period information indicating a validity period of the electronic certification; adding a time stamp to the calculated hash value; outputting the information, the electronic signature, the hash value, and the validity-period information to a storage device; and outputting, when it is determined that the information has not been tampered with, a verification result including information indicating that the information has not been tampered with.