In the present invention, a key acquisition part (411) acquires, from among multiple pairs of decryption keys and public keys, a decryption key ski from the conversion-source pair and a public key pkj from the conversion-destination pair. A conversion key generation part (412) encrypts, by using the public key pkj, the decryption key ski acquired by the key acquisition part (411) and generates a conversion key rki→j for converting a ciphertext encrypted using a public key pki from the conversion-source pair into a converted ciphertext which can be decrypted using a decryption key skj from the conversion-destination pair. An output part (413) outputs the conversion key rki→j generated by the conversion key generation part (412).
展开▼
机译：在本发明中，密钥获取部分（411）从多对解密密钥和公共密钥中，获取来自转换源对的解密密钥sk i 和公共密钥pk j 。转换密钥生成部分（412）通过使用公共密钥pk j 对由密钥获取部分（411）获取的解密密钥sk i 进行加密，并生成转换密钥rk i →j 用于将使用公钥pk i 加密的密文从转换源对转换为可转换的密文使用来自转换目标对的解密密钥sk j 解密。输出部分（413）输出由转换密钥生成部分（412）生成的转换密钥rk i →j 。
展开▼
