ECCBVerifyDSA

Verifies authenticity of the digital signature over a message digest (ECDSA).

Syntax

IppStatus ippsECCBVerifyDSA(const IppsBigNumState* pMsgDigest, const IppsBigNumState* pSignX, const IppsBigNumState* pSignY, IppECResult* pResult, IppsECCBState* pECC);

Parameters

pMsgDigest	Pointer to the message digest msg.
pSignX	Pointer to the integer r of the digital signature.
pSignY	Pointer to the integer s of the digital signature.
pResult	Pointer to the digital signature verification result.
pECC	Pointer to the context of the elliptic cryptosystem.

Description

This function is declared in the ippcp.h file.

The function verifies authenticity of the digital signature over a message digest msg. The signature consists of two large integers: r and s.

The scheme used to verify the signature is an elliptic curve analogue of the DSA scheme and assumes that the following cryptosystem key be hitherto set:

regPubKey

Message sender's regular public key.

The regPubKey is set by the function ECCBSetKeyPair.

The result of the digital signature verification can take one of two possible values:

ippECValid	Digital signature is valid.
ippECInvalidSignature	Digital signature is not valid.

The call to the ECCBVerifyDSA function must be preceded by the call to the ECCBSignDSA function which computes the digital signature over the message digest msg and represents the signature with two numbers: r and s.

The elliptic curve domain parameters must be hitherto defined by one of the functions: ECCBSet or ECCBSetStd.

For more information on digital signatures, please refer to the [ANSI] standard.

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 by pMsgDigest, pSignX, pSignY, or ECC is not valid.
ippStsMessageErr	Indicates an error condition if the value of msg pointed by pMsgDigest falls outside the range of [1, n-1] where n is the order of the elliptic curve base base point G.