/*

* 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>

EXPORT_C CDSASigner* CDSASigner::NewL(const CDSAPrivateKey& aKey)

	{

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

	return self;

	}

EXPORT_C CDSASigner* CDSASigner::NewLC(const CDSAPrivateKey& aKey) 

	{

	CDSASigner* self = NewL(aKey); 

	CleanupStack::PushL(self);

	return self;

	}

TInt CDSASigner::MaxInputLength(void) const

	{

	return SHA1_HASH;  // from hash.h

	}

CDSASignature* CDSASigner::SignL(const TDesC8& aInput) const

	{

	//see HAC 11.56 or DSS section 5

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

	//We don't check that r and s are non both non-null like the DSS

	//states you _optionally_ can.  The chances of this are _incredibly_ small.

	//You've got a much better chance of a bit failure ocurring in the hardware

	//than this.

	// a) Select a random secret integer (k | 0 < k < q)

	RInteger qminus1 = RInteger::NewL(iPrivateKey.Q());

	CleanupStack::PushL(qminus1);

	--qminus1;

	RInteger k = RInteger::NewRandomL(TInteger::One(), qminus1);

	CleanupStack::PopAndDestroy(&qminus1);

	CleanupStack::PushL(k);

	// b) compute r = (g^k mod p) mod q

	RInteger r = TInteger::ModularExponentiateL(iPrivateKey.G(), k, 	

		iPrivateKey.P());

	CleanupStack::PushL(r);

	r %= iPrivateKey.Q();

	// c) compute k^(-1) mod q 

	RInteger kinv = k.InverseModL(iPrivateKey.Q());

	CleanupStack::PushL(kinv);

	// d) compute s = k^(-1) * {h(m) + xr} mod q

	// 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);

	RInteger s = iPrivateKey.X().TimesL(r);

	CleanupStack::PushL(s);

	s += hm;

	s *= kinv;

	s %= iPrivateKey.Q();

	// e) signature for m is the pair (r,s)

	CDSASignature* signature = CDSASignature::NewL(r, s);//transfers ownership

	CleanupStack::Pop(&s);

	CleanupStack::PopAndDestroy(&hm);

	CleanupStack::PopAndDestroy(&kinv);

	CleanupStack::Pop(&r);

	CleanupStack::PopAndDestroy(&k);	

	return signature;

	}

CDSASigner::CDSASigner(const CDSAPrivateKey& aKey) 

	: iPrivateKey(aKey)

	{

	}