CONVERSION KEY GENERATION DEVICE, CIPHERTEXTCONVERSION DEVICE, DECRYPTION DEVICE, CIPHERTEXTCONVERSION SYSTEM, CONVERSION KEY GENERATION METHOD, CIPHERTEXTCONVERSION METHOD, DECRYPTION METHOD, AND PROGRAM

摘要

A conversion key generation device is characterized by having a key generation means for generating a conversion key utk_s→d to convert a first ciphertext ct_s based on a first public key cryptographic protocol ∑_s to a second ciphertext tct based on a second public key cryptographic protocol ∑_d by using a stochastic circuit or function secret sharing and inputting a decryption key sk_s for the first public key cryptographic protocol ∑_s and a public key pk_d for the second public key cryptographic protocol ∑_d.