![](/images/new-backgrounds/1225625/225625149x1.webp)
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| AI_EC_DHKeyAgree |
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an A_EC_PARAMS structure: |
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typedef struct | { |
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unsigned int | version; |
| /* implementation version */ |
unsigned int | fieldType; |
| /* indicates type of base field */ |
ITEM | fieldInfo; | /* The prime number if fieldType = FT_FP; */ | |
| /* the basis polynomial if fieldType = FT_F2_POLYNOMIAL; */ | ||
| /* and the degree of the field if fieldType = FT_F2_ONB */ | ||
ITEM | coeffA; |
| /* elliptic curve coefficient */ |
ITEM | coeffB; |
| /* elliptic curve coefficient */ |
ITEM | base; |
| /* elliptic curve group generator */ |
ITEM | order; | /* order of subgroup’s generating element */ | |
ITEM | cofactor; |
| /* the cofactor of the subgroup */ |
unsigned int | pointRepresentation; | /* not used. */ | |
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| /* set to CI_NO_COMPRESS as a default */ |
unsigned int | fieldElementBits; |
| /* field element size in bits */ |
} A_EC_PARAMS; |
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Format of info returned by B_GetAlgorithmInfo:
B_GetAlgorithmInfo is not supported with this AI. If called, it will return an error.
Crypto-C procedures to use with algorithm object:
B_KeyAgreeInit, B_KeyAgreePhase1, and B_KeyAgreePhase2. You must pass an initialized random algorithm to B_KeyAgreePhase1.
Algorithm methods to include in application's algorithm chooser:
AM_ECFP_DH_KEY_AGREE for odd prime fields and AM_ECF2POLY_DH_KEY_AGREE for even characteristic.
Output considerations:
The size of Phase 1 output is 1 + 2 · (size of field element) bytes; the size of Phase 2 output is (size of field element) bytes
C h a p t e r 2 A l g o r i t h m I n f o Ty p e s | 65 |