Extended key preparing apparatus, extended key preparing method, recording medium and computer program
First Claim
1. An extended key preparing apparatus wherein extended keys are prepared in common key cryptosystem from a cryptographic key input, comprising:
- a dividing unit which divides binary digit string of said cryptographic key into a plurality of elements each composed of a predetermined bit length;
an intermediate data preparing unit which prepares a plurality of intermediate data by applying a plurality of times an operation wherein a predetermined constant is used to the respective elements divided by said dividing unit;
a selecting unit which selects a plurality of intermediate data corresponding to the number of stages of extended keys from the plurality of the intermediate data prepared by said intermediate data preparing unit; and
an extended key preparing unit which prepares the extended keys corresponding to said number of stages by converting irreversibly the plurality of the intermediate data selected by said selecting unit.
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Accused Products
Abstract
Intermediate data ai, bi, ci, and di are prepared by an intermediate data preparing equipment 4 from a cryptographic key through a nonlinear type function operation and the like, an extended key preparing equipment 5 selects a [Xr], b [Yr], c [Zr], and d [Wr] corresponding to the number of stages r from the intermediate data, and rearranges the data as well as conducts that of bit operation to prepare extended keys, whereby an extended key preparing apparatus by which an extended key required in the case where common key cryptosystem is applied can be safely prepared at a high speed, a process for preparing such an extended key, and a recording medium used therefor are provided.
31 Citations
22 Claims
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1. An extended key preparing apparatus wherein extended keys are prepared in common key cryptosystem from a cryptographic key input, comprising:
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a dividing unit which divides binary digit string of said cryptographic key into a plurality of elements each composed of a predetermined bit length;
an intermediate data preparing unit which prepares a plurality of intermediate data by applying a plurality of times an operation wherein a predetermined constant is used to the respective elements divided by said dividing unit;
a selecting unit which selects a plurality of intermediate data corresponding to the number of stages of extended keys from the plurality of the intermediate data prepared by said intermediate data preparing unit; and
an extended key preparing unit which prepares the extended keys corresponding to said number of stages by converting irreversibly the plurality of the intermediate data selected by said selecting unit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An extended key preparing method wherein extended keys are prepared in common key cryptosystem from a cryptographic key input, comprising the steps of,
dividing binary digit string of said cryptographic key into a plurality of elements each composed of a predetermined bit length; -
preparing a plurality of intermediate data by applying the plurality of times an operation wherein a predetermined constant is used to the respective elements divided by said dividing step;
selecting a plurality of intermediate data corresponding to the number of stages of extended keys from the plurality of the intermediate data prepared by said intermediate data preparing step; and
preparing the extended keys corresponding to said number of stages by converting irreversibly the plurality of the intermediate data selected by said selecting step. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A computer readable recording medium wherein an extended key preparing program in which extended keys are prepared in common key cryptosystem from a cryptographic key input is to be recorded, comprising:
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recording the program containing a dividing step for dividing binary digit string of said cryptographic key into a plurality of elements each composed of a predetermined bit length;
an intermediate data preparing step for preparing a plurality of intermediate data by applying the plurality of times an operation wherein a predetermined constant is used to the respective elements divided by said dividing step;
a selecting step for selecting a plurality of intermediate data corresponding to the number of stages of extended keys from the plurality of the intermediate data prepared by said intermediate data preparing step; and
an extended key preparing step for preparing the extended keys corresponding to said number of stages by converting irreversibly the plurality of the intermediate data selected by said selecting step.
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22. An extended key preparing program in which extended keys are prepared in common key cryptosystem from a cryptographic key input, comprising:
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recording the program containing a dividing step for dividing binary digit string of said cryptographic key into a plurality of elements each composed of a predetermined bit length;
an intermediate data preparing step for preparing a plurality of intermediate data by applying the plurality of times an operation wherein a predetermined constant is used to the respective elements divided by said dividing step;
a selecting step for selecting a plurality of intermediate data corresponding to the number of stages of extended keys from the plurality of the intermediate data prepared by said intermediate data preparing step; and
an extended key preparing step for preparing the extended keys corresponding to said number of stages by converting irreversibly the plurality of the intermediate data selected by said selecting step.
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Specification