Data comparison device, data comparison system, and data comparison method

A data comparison system comprising:

• a data comparison device;
• a first encrypted data generation device that encrypts a first plaintext;
• and
• a second encrypted data generation device that encrypts a second plaintext, wherein
• the first encrypted data generation device
• divides the first plaintext into a plurality of blocks, and
• generates a first encrypted data by executing processing including encryption of the first plaintext for each of the plurality of blocks and shuffling of the plurality of blocks,
• the second encrypted data generation device
• divides the second plaintext into the plurality of blocks,
• generates a second encrypted data by executing processing including encryption of the second plaintext for each of the plurality of blocks,
• when at least one of processing of embedding a value of the first plaintext as a value indicating a magnitude comparison result in the generation of the first encrypted data by the first encrypted data generation device and processing of embedding a value of the second plaintext as a value indicating a magnitude comparison result in the generation of the second encrypted data by the second encrypted data generation device is executed,
• the first encrypted data generation device transmits the first encrypted data to the data comparison device and
• the second encrypted data generation device transmits the second encrypted data to the data comparison device, and
• the data comparison device compares blocks at the same position before shuffling of the first encrypted data and the second encrypted data based on the embedded value of the at least one plaintext and determines a magnitude relationship between the first plaintext and the second plaintext based on a value indicating the magnitude comparison result.

A data comparison method executed by a data comparison device, wherein

• the data comparison device includes a processor and a memory,
• the memory holds first encrypted data in which a first plaintext is encrypted and second encrypted data in which a second plaintext is encrypted,
• for the first plaintext divided into a plurality of blocks, the first encrypted data is data generated by executing processing including encryption of each of the plurality of blocks and shuffling of the plurality of blocks,
• for the second plaintext divided into the plurality of blocks, the second encrypted data is data generated by executing processing including encryption of each of the plurality of blocks,
• in at least one of the first encrypted data and the second encrypted data, a value of the at least one plaintext is embedded as a value indicating a magnitude comparison result, and
• the processor compares blocks at the same position before shuffling of the first encrypted data and the second encrypted data based on the embedded value of the at least one plaintext and determines a magnitude relationship between the first plaintext and the second plaintext.