Sony Corporation

Izuru Kitamura

Tsuyoshi Takagi

Masanobu Katagi

Toru Akishita

Yoshihito Ishibashi

Tomoyuki Asano

Jun Kitahara

A system and method for achieving secure and fast computation in hyperelliptic cryptography is realized. Fast scalar multiplication is achieve by executing computing operations including halving as computing processing in scalar multiplication with respect to a divisor D in hyperelliptic curve cryptography. For example, computing operations including halving are executed in scalar multiplication with respect to a divisor D on a hyperelliptic curve of genus 2 in characteristic 2 having h(x)=x+x+h, f=0 as parameters, a hyperelliptic curve of genus 2 in characteristic 2 having h(x)=x+hx+h, f=0 as parameters, or a hyperelliptic curve of genus 2 in characteristic 2 having h(x)=x as a parameter. Further, reduced complexity and faster computation are realized through the application of a table that records which of k, k', (k, k&#x2032;) is correct on the basis of a computed value of [&#xbd;D] with respect to a fixed divisor D, and through a reduction in the number of inversion operations.

Cryptographic computation method, cryptographic system, and computer program

An apparatus and a method for performing a hyperelliptic curve cryptography process at a high speed in a highly secure manner are provided. A base point D is produced such that the base point D and one or more of precalculated data in addition to the base point used in a scalar multiplication operation based on a window algorithm are degenerate divisors with a weight smaller than genus g of a hyperelliptic curve. An addition operation included in the scalar multiplication operation based on the window algorithm is accomplished by performing an addition operation of adding a degenerate divisor and a non-degenerate divisor, whereby a high-speed operation is achieved without causing degradation in security against key analysis attacks such as SPA.

Cryptographic processing apparatus

A cryptography-processing method for carrying out computation processing of hyperelliptic curve cryptography at a high speed and a cryptography-processing apparatus for implementing the method. In execution of scalar multiplication processing, a divisor is selected among divisors each having a weight g.sub.0 smaller than the genus g of a hyperelliptic curve where 1&#x2266;.g.&#x3c;g to serve as a base point. In hyperelliptic curve cryptography carried out in this configuration for a genus g of 2, computation processing of the scalar multiplication can be changed from HarleyADD to execution steps of ExHarADDwith a small number of computation-processing steps. For a genus g of 3, on the other hand, computation processing of the scalar multiplication can be changed from HarleyADD to execution steps of ExHarADD. or EXHarADD. with a small number of computation-processing steps. By changing the computation processing as described above, the processing speed can be increased.

Cryptography-processing method, cryptography-processing apparatus and computer program

Coded information can be utilized by devices other than a device supplied with information while preventing a dishonest use of the information, mutual recognizing part mutually recognizes the IC card . The coding part codes a key for contents with a key for movement. The recording part records coded contents and the key for contents coded by the coding part on the optical disc .

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Kanagawa, Japan

Izuru Kitamura