Hitachi, Ltd.

Seiji Miyazaki

Kazuo Takaragi

Seiichi Susaki

Katsuyuki Umezawa

Makoto Kitagawa

Hisashi Umeki

Kazuo Matsunaga

In an IC card incorporating residual multiplier hardware for implementing a high-speed algorithm for a residual multiplication arithmetic, a method and a device capable of executing a public key encryption processing such as an elliptic curve encryption processing at a high speed. Residual arithmetic succeeding to generation of a random number and residual arithmetic in a signature generating processing can be executed by using a residual multiplier. Further, in order to use effectively the residual multiplier for arithmetic operation on an elliptic curve, the point on the elliptic curve is transformed from a two-dimensional affine coordinate system to a three-dimensional coordinate system. Additionally, multiplicative inverse arithmetic for realizing reverse transformation from the three-dimensional coordinate system to the two-dimensional affine coordinate system as well as for determining a signature s can be executed only with the residual multiplication arithmetic. By making use of the residual multiplier in this manner, the processing speed can be increased. Computation complexity can be reduced by storing previously those parameters which are used frequently and constant multiplies of a base point of the elliptic curve in the form of tables, which also contributes to increasing of processing speed.

IC card equipped with elliptic curve encryption processing facility

In a data encryption/decryption method including an encryption step and a decryption step. In the encryption step, there are prepared n pairs of secret keys and public keys in a public-key cryptographic scheme, where n is a positive integer. A new key is generated in accordance with at least one of the public keys. Data is encrypted in a common-key cryptographic scheme by use of the new key. There is prepared a (k,n) threshold logic (k is an integer equal to or less than n) having terms associated with the new key and the n public keys. A calculation of the threshold logic is conducted by use of the new key and the n public keys, and encrypted data and a result of the calculation of the threshold logic are stored. In the decryption step, the new key is restored from k secret keys selected from the n secret keys and the stored result of the threshold logic calculation in accordance with a threshold reverse logic corresponding to the threshold logic and stored data is decrypted by the restored key in the common-key cryptographic scheme.

Network system using a threshold secret sharing method

In an IC card incorporating residual multiplier hardware for implementing a high-speed algorithm for a residual multiplication arithmetic, a method and a device capable of executing public key encryption processing such as an elliptic curve encryption processing at a high speed. Residual arithmetic succeeding to generation of a random number and residual arithmetic in a signature generating processing can be executed by using a residual multiplier. Further, in order to use effectively the residual multiplier for arithmetic operation on an elliptic curve, the point on the elliptic curve is transformed from a two-dimensional affine coordinate system to a three-dimensional coordinate system. Additionally, multiplicative inverse arithmetic for realizing reverse transformation from the three-dimensional coordinate system to the two-dimensional affine coordinate system as well as for determining a signature s can be executed only with the residual multiplication arithmetic. By making use of the residual multiplier in this manner, the processing speed can be increased. Computation complexity can be reduced by storing previously those parameters which are used frequently and constant multiplies of a base point of the elliptic curve in the form of tables, which also contributes to increasing of processing speed.

IC card equipped with elliptical curve encryption processing facility

A client-server system is provided in which access to a service by a user can properly be controlled, even if an approval by another user is required for receiving the service. First, the server,executes a log-in processing by using a user identifier and password transmitted from the client terminal,, and a user control file,. Next, the server,executes a service control by using a service supply request transmitted from the client terminal,and a service control file,provided with the server. When the server determines that an approval by another user is required for providing the service, the server executes the approval request to the client terminal,that the concerned user uses. When the reply to the approval request is affirmative, the server executes the processing in accordance with the foregoing service supply request. When the reply is negative, the server informs to the user who made the foregoing service supply request that the approval is rejected.

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Higashimurayama, Japan

Seiji Miyazaki