/*

* Copyright (c) 2003-2009 Nokia Corporation and/or its subsidiary(-ies).

* All rights reserved.

* This component and the accompanying materials are made available

* under the terms of the License "Eclipse Public License v1.0"

* which accompanies this distribution, and is available

* at the URL "http://www.eclipse.org/legal/epl-v10.html".

*

* Initial Contributors:

* Nokia Corporation - initial contribution.

*

* Contributors:

*

* Description: 

*

*/

#include <asymmetric.h>

#include <asymmetrickeys.h>

#include <bigint.h>

EXPORT_C CDSAVerifier* CDSAVerifier::NewL(const CDSAPublicKey& aKey)

	{

	CDSAVerifier* self = new(ELeave)CDSAVerifier(aKey);

	return self;

	}

EXPORT_C CDSAVerifier* CDSAVerifier::NewLC(const CDSAPublicKey& aKey)

	{

	CDSAVerifier* self = NewL(aKey);

	CleanupStack::PushL(self);

	return self;

	}

TInt CDSAVerifier::MaxInputLength(void) const

	{

	// return CSHA1::DIGESTBYTES

	return 160;

	}

TBool CDSAVerifier::VerifyL(const TDesC8& aInput, 

	const CDSASignature& aSignature) const

	{

	//see HAC 11.56 or DSS section 6

	//I'll follow HAC as I like the description better

	// a) Obtain A's authenticate public key

	// b) Verify that 0 < r < q and 0 < s < q; if not reject signature

	if (aSignature.R() <= 0 || aSignature.R() >= iPublicKey.Q())

		{

		return EFalse;

		}

	if (aSignature.S() <= 0 || aSignature.S() >= iPublicKey.Q())

		{

		return EFalse;

		}

	TBool result = EFalse;

	// c) Compute w = s^(-1) mod q and h(m)

	RInteger w = aSignature.S().InverseModL(iPublicKey.Q());

	CleanupStack::PushL(w);

	// Note that in order to be interoperable, compliant with the DSS, and

	// secure, aInput must be the result of a SHA-1 hash

	RInteger hm = RInteger::NewL(aInput);

	CleanupStack::PushL(hm);

	// d) Compute u1 = w * hm mod q and u2 = r * w mod q

	RInteger u1 = TInteger::ModularMultiplyL(w, hm, iPublicKey.Q());

	CleanupStack::PushL(u1);

	RInteger u2 = TInteger::ModularMultiplyL(aSignature.R(), w, iPublicKey.Q());

	CleanupStack::PushL(u2);

	// e) Compute v = ((g^u1 * y^u2) mod p) mod q

	RInteger temp = TInteger::ModularExponentiateL(iPublicKey.G(), u1,

		iPublicKey.P());

	CleanupStack::PushL(temp);

	RInteger temp1 = TInteger::ModularExponentiateL(iPublicKey.Y(), u2,

		iPublicKey.P());

	CleanupStack::PushL(temp1);

	RInteger v = TInteger::ModularMultiplyL(temp, temp1, iPublicKey.P());

	CleanupStack::PushL(v);

	v %= iPublicKey.Q();

	// f) Accept the signature iff v == r

	if(v == aSignature.R())

		{

		result = ETrue;

		}

	CleanupStack::PopAndDestroy(&v);

	CleanupStack::PopAndDestroy(&temp1);

	CleanupStack::PopAndDestroy(&temp);

	CleanupStack::PopAndDestroy(&u2);

	CleanupStack::PopAndDestroy(&u1);

	CleanupStack::PopAndDestroy(&hm);

	CleanupStack::PopAndDestroy(&w); 

	return result;	

	}

CDSAVerifier::CDSAVerifier(const CDSAPublicKey& aKey)  

	: iPublicKey(aKey)

	{

	}