CYPHER SYSTEM, KEY GENERATION APPARATUS, ENCRYPTION APPARATUS, DECRYPTION APPARATUS, METHOD AND PROGRAM
An encryption system includes one or more computers each including a memory and a processor configured to generating a public key and a master private key that are used in attribute-based encryption; using, as inputs, at least the public key and one of an attribute and a policy that is denoted by an arbitrary conditional expression related to the attribute, and generating at least cyphertext in which one of the attribute and the policy is embedded; using the public key, the master private key, and the other of the attribute and the policy as inputs, and generating a private key in which the other of the attribute and the policy is embedded; and using the public key, the cyphertext, and the private key as inputs, and decrypting the cyphertext.
1 . An encryption system, comprising:
one or more computers each including a memory and a processor configured to generating a public key and a master private key that are used in attribute-based encryption;
using, as inputs, at least the public key and one of an attribute and a policy that is denoted by an arbitrary conditional expression related to the attribute, and generating at least cyphertext in which one of the attribute and the policy is embedded;
using the public key, the master private key, and the other of the attribute and the policy as inputs, and generating a private key in which the other of the attribute and the policy is embedded; and
using the public key, the cyphertext, and the private key as inputs, and decrypting the cyphertext.
2 . A key generation apparatus, comprising:
a memory and a processor configured to generating a public key and a master private key that are used in attribute-based encryption; and
using, as inputs, the public key, the master private key, and one of an attribute and a policy that is denoted by an arbitrary conditional expression related to the attribute, and generating a private key in which one of the attribute and the policy is embedded.
3 - 4 . (canceled)
5 . A method executed by a computer including a memory and a processor, the method comprising:
generating a public key and a master private key that are used in attribute-based encryption;
an encryption procedure of using, as inputs, at least the public key and one of an attribute and a policy that is denoted by an arbitrary conditional expression related to the attribute, and generating at least cyphertext in which one of the attribute and the policy is embedded;
using the public key, the master private key, and the other of the attribute and the policy as inputs, and generating a private key in which the other of the attribute and the policy is embedded; and
using the public key, the cyphertext, and the private key as inputs, and decrypting the cyphertext.
6 . A non-transitory computer-readable recording medium having computer-readable instructions stored thereon, which when executed, cause a computer including a memory and a processor to execute respective operations in the encryption system according to claim 1 or respective operations in the key generation apparatus according to claim 2 .