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 a bit string of said cryptographic key into a plurality of bit groups, each bit group having a predetermined bit length;
an intermediate data preparing unit which prepares a plurality of intermediate data groups from the bit groups by a predetermined operation with different constant for each bit group, each intermediate data group having first intermediate data;
a selecting unit which selects one item of the first intermediate data for each of the intermediate data groups depending on a number of stages of extended keys to determine second intermediate data; and
an extended key preparing unit which prepares the extended keys having a bit length longer than the bit string of said cryptographic key by converting irreversibly the second intermediate data, wherein said intermediate data preparing unit is provided with a nonlinear type operating unit for effecting a nonlinear type operation with respect to each bit group to prepare the intermediate data groups.
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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.
14 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 a bit string of said cryptographic key into a plurality of bit groups, each bit group having a predetermined bit length;
an intermediate data preparing unit which prepares a plurality of intermediate data groups from the bit groups by a predetermined operation with different constant for each bit group, each intermediate data group having first intermediate data;
a selecting unit which selects one item of the first intermediate data for each of the intermediate data groups depending on a number of stages of extended keys to determine second intermediate data; and
an extended key preparing unit which prepares the extended keys having a bit length longer than the bit string of said cryptographic key by converting irreversibly the second intermediate data, wherein said intermediate data preparing unit is provided with a nonlinear type operating unit for effecting a nonlinear type operation with respect to each bit group to prepare the intermediate data groups. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An extended key preparing method wherein extended keys are prepared in common key cryptosystem from a cryptographic key input, comprising:
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dividing a bit string of said cryptographic key into a plurality of bit groups, each bit group having a predetermined bit length;
preparing a plurality of intermediate data groups from the bit groups by effecting a nonlinear type operation with different constant for each bit group, each intermediate data group having a first intermediate data;
selecting one item of the first intermediate data for each of the intermediate data groups depending on a number of stages of extended keys to determine second intermediate data; and
preparing the extended keys having a bit length longer than the bit string of said cryptographic key by converting irreversibly the second intermediate data. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. 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, the program comprising program code means which when executed perform:
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dividing a bit string of said cryptographic key into a plurality of bit groups, each bit group having a predetermined bit length;
preparing a plurality of intermediate data groups from the bit groups by effecting a nonlinear type operation with different constant for each bit group, each intermediate data group having a first intermediate data;
one item of the first intermediate data for each of the intermediate data groups depending on a number of stages of extended keys to determine second intermediate data; and
preparing the extended keys having a bit length longer than the bit string of said cryptographic key by converting irreversibly the second intermediate data.
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20. An extended key preparing program in which extended keys are prepared in common key cryptosystem from a cryptographic key input, the program comprising program code means which when executed perform:
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dividing a bit string of said cryptographic key into a plurality of bit groups, each bit group having a predetermined bit length;
preparing a plurality of intermediate data groups from the bit group by effecting a nonlinear type operation with different constant for each bit group, each intermediate data group having first intermediate data;
one item of the intermediate data for each of the intermediate data groups depending on a number of stages of extended keys to determine second intermediate data; and
preparing the extended keys having a bit length longer than the bit string of said cryptographic key by converting irreversibly the second intermediate data.
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21. 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, said intermediate data preparing unit being provided with a nonlinear type operating unit for effecting nonlinear type operation with respect to the respective elements divided by said dividing unit, said nonlinear type operating unit performing nonlinear type operation in such a manner that when said cryptographic key is divided into eight elements of 32 bits by said dividing unit, said nonlinear type operating unit separates said elements into 6, 5, 5, 5, 5, and 6 bits to transpose the same into other data, respectively, and the data after transposition are subjected to nonlinear type operation by the use of a determinant 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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22. 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, said preparing involving a nonlinear type operating step for effecting nonlinear type operation with respect to the respective elements divided by said dividing step, said nonlinear type operating step performing a nonlinear type operation in such a manner that when said cryptographic key is divided into eight elements of 32 bits by said dividing step, said nonlinear type operating step separates said elements into 6, 5, 5, 5, 5, and 6 bits to transpose the same into other data, respectively, and the data after transposition are subjected to nonlinear type operation by the use of a determinant;
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.
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Specification