Abstract: A server sends a key update request for requesting updating of the key, to a client terminal. The client terminal sends, to a key delivery server, a key delivery request for requesting the delivery of a key to the client terminal. The key delivery server delivers a key to the client terminal. The client terminal sends, to the server, a key reception notice indicating that the delivered key was received. The server sends, to the client terminal, a key-use start notice indicating that the client terminal starts data transmission and reception by using the delivered key with a different client terminal from the aforementioned client terminal. The client terminal performs data transmission and reception with the different client terminal by using the delivered key.

Abstract: The risk of leakage of secret information caused by leakage of a secret key is reduced. A segmented secret-key storage system segments a secret key SK into segments that can be combined at the time of decryption or at the time of generation of a signature and records the secret-key segments sk1, . . . , skN in segment storage apparatuses. The secret-key segments are changed, periodically or under a predetermined condition, to another set of secret-key segments that satisfies a condition for combination. In the segmented secret-key storage system, the secret key SK is not revealed unless the secret-key segments are stolen from all the segment storage apparatuses in an interval between changes made to the secret-key segments. Accordingly, the risk of leakage can be greatly reduced in comparison with the risk of leakage of the secret key from a single apparatus.

Abstract: An assumed use permission range storage stores a predetermined assumed use permission range. An unavailable state storage stores an information asset in an unavailable state by encryption. An available state storage stores an information asset in an available state by decryption. A leakage-concerned state storage stores an information asset in a leakage-concerned state. When use of an information asset in the unavailable state is requested by an application corresponding to the assumed use permission range, a state changing part decrypts the information asset into the available state. When use of the information asset in the available state by the application ends, the state changing part encrypts the information asset into the unavailable state. When use of an information asset in the unavailable state is requested by an application not corresponding to the assumed use permission range, a state monitoring part puts the information asset in the leakage-concerned state.

Abstract: Plurality of users share a common key while permitting dynamic member change and computational complexity required for key exchange is reduced. The first key generation unit 212 of the communication devices Ui computes Ri and ci, or ci based on a twisted pseudo-random function. A session ID generation unit 113 of a key distribution device S generates sid based on a target-collision resistant hash function and transmits sid to the communication devices Ui. A second key generation unit 214 of the communication devices Ui computes Ti based on a pseudo-random function. A third key generation unit 115 of the key distribution device S computes k? and T?i based on the twisted pseudo-random function. A session key generation unit 217 of the communication devices Ui generates the common key K2 based on a pseudo-random function.

Abstract: A private key is held which conforms to an ElGamal encryption system on a semigroup, calculation of an order of an element of the semigroup being computationally difficult, information corresponding to ciphertext conforming to the ElGamal encryption system is input, a private key s is used to decrypt the information corresponding to the ciphertext in conformance to the ElGamal encryption system, and information corresponding to a result of decrypting the ciphertext is obtained and output. Alternatively, whether it is computationally difficult or easy to calculate the order of the element of the semigroup is determined, and the safety of a decryption service providing device is evaluated based on the determination result.

Abstract: At the time of setting authority, a management apparatus stores a database in which authority information corresponding to authority to physically drive a drive apparatus, which is a tangible object, using a terminal apparatus, and registration identification information corresponding to a subject that is given the authority are associated, and outputs information representing any of the registration identification information; and a permission apparatus receives and stores the information. At the time of exercising the authority, the terminal apparatus outputs information representing identification information, and the permission apparatus receives the information and, when the identification information corresponds to registration identification information comprised in setting information, outputs information representing authority exercise information required to exercise the authority.

Abstract: A key storage apparatus which prevents a service from being resumed with the same configuration as a configuration during an arithmetic processing provision period, a key storage method, and a program therefor. The key storage apparatus is such that it is assumed that, before expiration of a period for providing arithmetic processing using a key, the key is secretly managed, and that the key is outputted when the period expires, and the key storage apparatus comprises: a one-way function section causing a one-way function to act on first information to generate the key; a storage section secretly storing the first information during the period; and an expiration judging section eliminating the first information from the storage section and outputting the key when the period expires.

Abstract: The risk of leakage of secret information caused by leakage of a secret key is reduced. A segmented secret-key storage system segments a secret key SK into segments that can be combined at the time of decryption or at the time of generation of a signature and records the secret-key segments sk1, . . . , skN in segment storage apparatuses. The secret-key segments are changed, periodically or under a predetermined condition, to another set of secret-key segments that satisfies a condition for combination. In the segmented secret-key storage system, the secret key SK is not revealed unless the secret-key segments are stolen from all the segment storage apparatuses in an interval between changes made to the secret-key segments. Accordingly, the risk of leakage can be greatly reduced in comparison with the risk of leakage of the secret key from a single apparatus.

Abstract: A private key is held which conforms to an ElGamal encryption system on a semigroup, calculation of an order of an element of the semigroup being computationally difficult, information corresponding to ciphertext conforming to the ElGamal encryption system is input, a private key s is used to decrypt the information corresponding to the ciphertext in conformance to the ElGamal encryption system, and information corresponding to a result of decrypting the ciphertext is obtained and output. Alternatively, whether it is computationally difficult or easy to calculate the order of the element of the semigroup is determined, and the safety of a decryption service providing device is evaluated based on the determination result.