GFpECPSharedSecretDH, GFpECPSharedSecretDHC

Computes a shared secret field element by using the Diffie-Hellman scheme.

Syntax

IppStatus ippsGFpECSharedSecretDH(const IppsBigNumState* pPrivateA, const IppsGFpECPoint* pPublicB, IppsBigNumState* pShare, IppsGFpECState* pEC, Ipp8u* pScratchBuffer);

IppStatus ippsGFpECSharedSecretDHC(const IppsBigNumState* pPrivateA, const IppsGFpECPoint* pPublicB, IppsBigNumState* pShare, IppsGFpECState* pEC, Ipp8u* pScratchBuffer);

Include Files

ippcp.h

Parameters

pPrivateA	Pointer to your own private key privKey.
pPublicB	Pointer to the public key pubKey.
pShare	Pointer to the secret number bnShare.
pEC	Pointer to the context of the elliptic curve.
pScratchBuffer	Pointer to the scratch buffer of size produced by ippsGFpECScratchBufferSize.

Description

The function computes a secret number bnShare, which is a secret key shared between two participants of the cryptosystem.

The ippsGFpECSharedSecretDH function computes elliptic point P =[pPrivateA]· pPublicB. In the ippsGFpECSharedSecretDHC function the h cofactor is used: P =[h][pPrivateA]· pPublicB.

The ippsGFpECScratchBufferSize function should be called with nScalars equal to at least 1 to get the valid pScratchBuffer.

Return Values

ippStsNoErr	Indicates no error. Any other value indicates an error or warning.
ippStsNullPtrErr	Indicates an error condition if any of the specified pointers is NULL.
ippStsContextMatchErr	Indicates an error condition if one of the contexts pointed to by pPublicB, pPrivateA, pShare, or pEC is not valid.
ippStsRangeErr	Indicates an error condition if the memory size of bnShare pointed to by pShare is less than the size of the GFp modulus that is base for the specified elliptic curve.
ippStsShareKeyErr	Indicates an error condition if the shared secret key is not valid. (For example, the shared secret key is invalid if the result of the secret point calculation is the point at infinity.)