Patent ID: 8458479

Claim:
A verification apparatus comprising a processing device, an integer partitioning unit, a verification value calculation unit, and a verification judging unit, wherein, using the processing device, the integer partitioning unit inputs an order p of a finite group G and an integer e, the order p and the integer e being calculated based on a ciphertext, and calculates an integer e 1 and an integer e 2 that satisfy e 1 ·e≡e 2 (mod p) based on the order p and the integer e which are input, wherein, using the processing device, the verification value calculation unit inputs an element s of the finite group G and an element h of the finite group G, the element s and the element h being calculated based on the ciphertext, and calculates an element a(=e 1 ·h−e 2 ·s) of the finite group G based on the element s and the element h which are input and the integer e 1 and the integer e 2 which are calculated by the integer partitioning unit, and wherein the verification judging unit judges, using the processing device and based on the element a calculated by the verification value calculation unit, that verification of the ciphertext is successful when the element a is an identity element of the finite group G.