1 /*

     2 * Copyright (c) 2006-2009 Nokia Corporation and/or its subsidiary(-ies).

     3 * All rights reserved.

     4 * This component and the accompanying materials are made available

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

     6 * which accompanies this distribution, and is available

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

     8 *

     9 * Initial Contributors:

    10 * Nokia Corporation - initial contribution.

    11 *

    12 * Contributors:

    13 *

    14 * Description: 

    15 *

    16 */

    17 

    18 

    19 #include "dsasignerimpl.h"

    20 #include "pluginconfig.h"

    21 

    22 using namespace SoftwareCrypto;

    23 

    24 // Implementation of CDSASignerImpl 

    25 CDSASignerImpl* CDSASignerImpl::NewL(const CKey& aKey)

    26 	{

    27 	CDSASignerImpl* self = CDSASignerImpl::NewLC(aKey);

    28 	CleanupStack::Pop(self);

    29 	return self;

    30 	}

    31 	

    32 CDSASignerImpl* CDSASignerImpl::NewLC(const CKey& aKey)

    33 	{

    34 	CDSASignerImpl* self = new(ELeave) CDSASignerImpl();

    35 	CleanupStack::PushL(self);

    36 	self->ConstructL(aKey);

    37 	return self;

    38 	}

    39 

    40 CDSASignerImpl::CDSASignerImpl() 

    41 	{

    42 	}

    43 	

    44 CDSASignerImpl::~CDSASignerImpl()

    45 	{

    46 	}

    47 	

    48 void CDSASignerImpl::ConstructL(const CKey& aKey)

    49 	{

    50 	CSignerImpl::ConstructL(aKey);

    51 	}

    52 

    53 CExtendedCharacteristics* CDSASignerImpl::CreateExtendedCharacteristicsL()

    54 	{

    55 	// All Symbian software plug-ins have unlimited concurrency, cannot be reserved

    56 	// for exclusive use and are not CERTIFIED to be standards compliant.

    57 	return CExtendedCharacteristics::NewL(KMaxTInt, EFalse);

    58 	}

    59 

    60 const CExtendedCharacteristics* CDSASignerImpl::GetExtendedCharacteristicsL()

    61 	{

    62 	return CDSASignerImpl::CreateExtendedCharacteristicsL();

    63 	}

    64 

    65 TUid CDSASignerImpl::ImplementationUid() const

    66 	{

    67 	return KCryptoPluginDsaSignerUid;

    68 	}

    69 	

    70 void CDSASignerImpl::SetKeyL(const CKey& aPrivateKey) 

    71 	{

    72 	DoSetKeyL(aPrivateKey);

    73 	Reset();

    74 	}

    75 

    76 TInt CDSASignerImpl::GetMaximumInputLengthL() const 

    77 	{

    78 	return KSha1HashLength;

    79 	}

    80 

    81 void CDSASignerImpl::SignL(const TDesC8& aInput, CCryptoParams& aSignature) 

    82 	{

    83 	

    84 	//see HAC 11.56 or DSS section 5

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

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

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

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

    89 	//than this.

    90 

    91 	const TInteger& tQ=iKey->GetBigIntL(KDsaKeyParameterQUid);

    92 		

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

    94 	RInteger qminus1 = RInteger::NewL(tQ);

    95 	CleanupStack::PushL(qminus1);

    96 	--qminus1;

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

    98 	CleanupStack::PopAndDestroy(&qminus1);

    99 	CleanupStack::PushL(k);

   100 	

   101 	

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

   103 	

   104 	const TInteger& tG=iKey->GetBigIntL(KDsaKeyParameterGUid);

   105 	const TInteger& tP=iKey->GetBigIntL(KDsaKeyParameterPUid);

   106 	RInteger r = TInteger::ModularExponentiateL(tG, k, tP);

   107 	CleanupStack::PushL(r);

   108 	r %=tQ;

   109 	

   110 	

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

   112 

   113 	RInteger kinv = k.InverseModL(tQ);

   114 	CleanupStack::PushL(kinv);

   115 

   116 

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

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

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

   120 

   121 	RInteger hm = RInteger::NewL(aInput);

   122 	CleanupStack::PushL(hm);

   123 	

   124 	const TInteger& tX=iKey->GetBigIntL(KDsaKeyParameterXUid);	

   125 	RInteger s = tX.TimesL(r);

   126 	CleanupStack::PushL(s);

   127 	s += hm;

   128 	s *= kinv;

   129 	s %= tQ;

   130 

   131 

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

   133 	aSignature.AddL(r, KDsaSignatureParameterRUid);

   134 	aSignature.AddL(s, KDsaSignatureParameterSUid);

   135 	

   136 	CleanupStack::PopAndDestroy(5, &k);

   137 	}