| 摘要 |
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≰.g0.<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 ExHarADD2+1→2 with 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 ExHarADD3+→3. or EXHarADD3+1→3. with a small number of computation-processing steps. By changing the computation processing as described above, the processing speed can be increased.
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