Contents

GFpInit

Initializes the context of a prime finite field GF(q).

Syntax

IppStatus ippsGFpInit(const IppsBigNumState* pPrime, int primeBitSize, const IppsGFpMethod* method, IppsGFpState* pGF);

Include Files

ippcp.h

Parameters

pPrime

Pointer to the Big Number context storing the GF(q) modulus.

primeBitSize

Size, in bytes, of the odd prime number p (modulus of GF(q)).

method

Pointer to the implementation of a basic arithmetic (methods) over the prime finite field GF(q).

pGF

Pointer to the context of the GF(q) field being initialized.

Note

If your application uses one of predefined values of the modulus q, the use of the GFpMethod function corresponding to that value is preferable. In other cases, use ippsGfpMethod_pArb().

Description

The function initializes the pGF context parameter with the values of the input parameterspPrime, primeBitSize, and method. The three parameters have to be compatible with each other.

The method parameter must be an output from one of the GFpMethod functions with predefined modulus q, and the parameters primeBitSize and method must be compatible with each other.

If pPrime is not NULL, and method is an output from one of the GFpMethod functions with predefined modulus q, then the pair pPrime and primeBitSize should define the same prime q as defined in method.

If both pPrime and method are not NULL, then ippsGFpInit() provides the required initialization if the parameters are compatible with each other.

The initialized context is used in the functions that create contexts of elements of the GF(p) field, which, in turn, are used to perform operations with the field elements.

Note

This function does not check if pPrime actually refers to a prime value.

Return Values

ippStsNoErr

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

ippStsNullPtrErr

Indicates an error condition in the following cases:

  • pGF is NULL.

  • Both pPrime and method are NULL.

ippStsSizeErr

Indicates an error condition if primeBitSize is less than 2 or greater than 1024.

ippStsContextMatchErr

Indicates an error condition if the pPrime context parameter is not NULL and does not match the operation.

ippStsBadArgErr

Indicates an error condition in the following cases:

  • The modulus q defined in pPrime is less than 3.

  • bitsize(q) != primeBitSize.

  • q is even.

  • method is not NULL and not an output of GFpMethod.

  • method is an output from one of the GFpMethod functions with predefined modulus q, but:

    • The bit size of q of method is different from the bit size of the value stored in the context pointed to by pPrime.

    • q of method is different from the value stored in the context pointed to by pPrime.

previous

Finite Field Arithmetic

next

GFpMethod