Contents

GFpECGetSubgroup

Extracts the parameters (base point and its order) that define an elliptic curve point subgroup.

Syntax

IppStatus ippsGFpECGetSubGroup(IppsGFpState** const ppGF, IppsGFpElement* pX, IppsGFpElement* pY, IppsBigNumState* pOrder,IppsBigNumState* pCofactor, const IppsGFpECState* pEC);

Include Files

ippcp.h

Parameters

ppGF

Pointer to the context of the underlying finite field.

pX, pY

Pointers to the X and Y coordinates of the base point of the elliptic curve.

pOrder

Pointer to the big number context storing the order of the base point.

pCofactor

Pointer to the big number context storing the cofactor.

pEC

Pointer to the context of the elliptic curve.

Description

This function extracts parameters of an elliptic curve subgroup. You can get any combination of the following parameters: the X and Y coordinates, the order of the base point, and the value of the cofactor. To turn off extraction of a particular parameter of the elliptic curve, set the appropriate function parameter to NULL.

Return Values

ippStsNoErr

Indicates no error. Any other value indicates an error or warning.

ippStsNullPtrErr

Indicates an error condition if the specified pointer pEC is NULL.

ippStsContextMatchErr

Indicates an error condition in the following cases:

  • IppsGFpECState context parameter does not match the operation.

  • Any of the pointers to elliptic curve parameters is not zero and the corresponding context parameter does not match the operation.

ippStsOutOfRangeErr

Indicates an error if the base point coordinates (pX, pY) do not belong to the finite field over which the elliptic curve is initialized.

ippStsLengthErr

Indicates an error condition in the following cases:

  • The size of the base point order exceeds the maximal size of the order for the given curve.

  • The bit size of the cofactor exceeds the bit size of the element of the finite field over which the elliptic curve is initialized.

previous

GFpECGet

next

GFpECScratchBufferSize