Digital data content certification system, data certification device, user terminal, computer program and method therefor

A non-transitory computer-readable medium storing instructions that, when executed by a processor, cause the processor to perform a process comprising:

• creating a certificate file containing date and time of receipt of the digital data and attaching the digital data to the certificate file to create an intermediate file;
• transmitting the intermediate file to a time stamping device
• feeding the intermediate file into a predetermined hash function to calculate a hash value and transmitting the calculated hash value instead of the intermediate file to the time stamping device;
• receiving, by the computer, date and time certification information containing the hash value and date and time at which the time stamping device receives the intermediate file from the time stamping device;
• embedding, by the computer, the date and time certification information received from the time stamping device into the intermediate file to create a certified file;
• creating, by the computer, verification software configured to verify the certified file by calculating a second hash value of a file obtained by deleting the date and time certification information from the certified file, comparing the first hash value with the second hash value, and outputting the result of comparison between hash values, wherein the original data is verified when the result of comparison indicates that the first hash value and the second hash value are the same;
• and
• transmitting, by the computer, the certified file and the verification software to the user terminal.

A method for certifying existence of digital data at a time point, comprising:

• receiving, by a computer configured to be connected to a user terminal and a time stamping device via the Internet, digital data to be certified from the user terminal;
• creating, by the computer, a certificate file containing date and time of receipt of the received original data and attaching the original data to the certificate file to create an intermediate file;
• transmitting, by the computer, the intermediate file to the time stamping device
• feeding the intermediate file into a predetermined hash function to calculate a hash value and transmitting the calculated hash value instead of the intermediate file to the time stamping device;
• receiving, by the computer, date and time certification information containing the hash value and date and time at which the time stamping device receives the intermediate file from the time stamping device;
• embedding, by the computer, the date and time certification information received from the time stamping device into the intermediate file to create a certified file;
• creating, by the computer, verification software configured to verify the certified file by calculating a second hash value of a file obtained by deleting the date and time certification information from the certified file, comparing the first hash value with the second hash value, and outputting the result of comparison between hash values, wherein the original data is verified when the result of comparison indicates that the first hash value and the second hash value are the same;
• and
• transmitting, by the computer, the certified file and the verification software to the user terminal.