Processing apparatus, processing method, storage medium, and encryption processing system

A processing method by a processing apparatus for executing a predetermined process by using encrypted data based on homomorphic encryption as an input while maintaining a secret state by encryption, the processing method comprising:

• in executing a calculation corresponding to a processing of multiplying plaintext data by a predetermined multiplier,
• generating a first calculation result based on a first multiplier component of the predetermined multiplier, the first multiplier component being a component that is not used in a calculation of encrypted data,
• generating a second calculation result by executing a calculation to encrypted data input in a ciphertext space corresponding to multiplication of the plaintext data by a second multiplier component of the predetermined multiplier, the second multiplier component being a component other than the first multiplier component, and
• outputting the first calculation result and the second calculation result in association with each other.

A non-transitory computer readable storage medium storing a processing program causing a computer to execute a process, for executing a predetermined process by using encrypted data based on homomorphic encryption as an input while maintaining a secret state by encryption to execute the process, the process including:

• in executing a calculation corresponding to a processing of multiplying plaintext data by a predetermined multiplier,
• generating a first calculation result based on a first multiplier component of the predetermined multiplier, the first multiplier component being a component that is not used in a calculation of encrypted data,
• generating a second calculation result by executing a calculation to encrypted data input in a ciphertext space corresponding to multiplication of the plaintext data by a second multiplier component of the predetermined multiplier, the second multiplier component being a component other than the first multiplier component, and
• outputting the first calculation result and the second calculation result in association with each other.

An encryption processing system comprising:

• a processing apparatus for executing a predetermined process by using encrypted data based on homomorphic encryption as an input while maintaining a secret state by encryption;
• and
• a result generation apparatus for executing a process for generating a result corresponding to plaintext data by using a processing result by the processing apparatus as an input, wherein
• the processing apparatus includes at least one processor configured to function as
• an input unit that receives the encrypted data, and
• a process execution unit that executes the predetermined process by using the encrypted data and to include one or more processing units at least one of which is a multiplication corresponding processing unit for executing a calculation corresponding to a process of multiplying the plaintext data by a predetermined multiplier, the multiplication corresponding processing unit generating a first calculation result based on a first multiplier component of the predetermined multiplier, the first multiplier component being a component that is not used in a calculation of encrypted data, generating a second calculation result by executing a calculation to encrypted data input in a ciphertext space corresponding to multiplication of the plaintext data by a second multiplier component of the predetermined multiplier, the second multiplier component being a component other than the first multiplier component, and outputting the first calculation result and the second calculation result in association with each other, and
• the result generation apparatus includes at least one processor configured to function as
• a processing result reception unit that receives the processing result including a first processing result and a second processing result from the processing apparatus,
• a decryption unit that decrypts the second processing result, and
• a reflection processing unit that executes a reflection process for reflecting the first processing result on the plaintext data decrypted by the decryption unit.