~zooko/cryptopp/trunk : contents of ec2n.cpp at revision 269

~zooko/cryptopp/trunk : (revision 269)

// ec2n.cpp - written and placed in the public domain by Wei Dai

#include "pch.h"

#ifndef CRYPTOPP_IMPORTS

#include "ec2n.h"
#include "asn.h"

#include "algebra.cpp"
#include "eprecomp.cpp"

NAMESPACE_BEGIN(CryptoPP)

EC2N::EC2N(BufferedTransformation &bt)
	: m_field(BERDecodeGF2NP(bt))
{
	BERSequenceDecoder seq(bt);
	m_field->BERDecodeElement(seq, m_a);
	m_field->BERDecodeElement(seq, m_b);
	// skip optional seed
	if (!seq.EndReached())
		BERDecodeOctetString(seq, TheBitBucket());
	seq.MessageEnd();
}

void EC2N::DEREncode(BufferedTransformation &bt) const
{
	m_field->DEREncode(bt);
	DERSequenceEncoder seq(bt);
	m_field->DEREncodeElement(seq, m_a);
	m_field->DEREncodeElement(seq, m_b);
	seq.MessageEnd();
}

bool EC2N::DecodePoint(EC2N::Point &P, const byte *encodedPoint, size_t encodedPointLen) const
{
	StringStore store(encodedPoint, encodedPointLen);
	return DecodePoint(P, store, encodedPointLen);
}

bool EC2N::DecodePoint(EC2N::Point &P, BufferedTransformation &bt, size_t encodedPointLen) const
{
	byte type;
	if (encodedPointLen < 1 || !bt.Get(type))
		return false;

	switch (type)
	{
	case 0:
		P.identity = true;
		return true;
	case 2:
	case 3:
	{
		if (encodedPointLen != EncodedPointSize(true))
			return false;

		P.identity = false;
		P.x.Decode(bt, m_field->MaxElementByteLength()); 

		if (P.x.IsZero())
		{
			P.y = m_field->SquareRoot(m_b);
			return true;
		}

		FieldElement z = m_field->Square(P.x);
		assert(P.x == m_field->SquareRoot(z));
		P.y = m_field->Divide(m_field->Add(m_field->Multiply(z, m_field->Add(P.x, m_a)), m_b), z);
		assert(P.x == m_field->Subtract(m_field->Divide(m_field->Subtract(m_field->Multiply(P.y, z), m_b), z), m_a));
		z = m_field->SolveQuadraticEquation(P.y);
		assert(m_field->Add(m_field->Square(z), z) == P.y);
		z.SetCoefficient(0, type & 1);

		P.y = m_field->Multiply(z, P.x);
		return true;
	}
	case 4:
	{
		if (encodedPointLen != EncodedPointSize(false))
			return false;

		unsigned int len = m_field->MaxElementByteLength();
		P.identity = false;
		P.x.Decode(bt, len);
		P.y.Decode(bt, len);
		return true;
	}
	default:
		return false;
	}
}

void EC2N::EncodePoint(BufferedTransformation &bt, const Point &P, bool compressed) const
{
	if (P.identity)
		NullStore().TransferTo(bt, EncodedPointSize(compressed));
	else if (compressed)
	{
		bt.Put(2 + (!P.x ? 0 : m_field->Divide(P.y, P.x).GetBit(0)));
		P.x.Encode(bt, m_field->MaxElementByteLength());
	}
	else
	{
		unsigned int len = m_field->MaxElementByteLength();
		bt.Put(4);	// uncompressed
		P.x.Encode(bt, len);
		P.y.Encode(bt, len);
	}
}

void EC2N::EncodePoint(byte *encodedPoint, const Point &P, bool compressed) const
{
	ArraySink sink(encodedPoint, EncodedPointSize(compressed));
	EncodePoint(sink, P, compressed);
	assert(sink.TotalPutLength() == EncodedPointSize(compressed));
}

EC2N::Point EC2N::BERDecodePoint(BufferedTransformation &bt) const
{
	SecByteBlock str;
	BERDecodeOctetString(bt, str);
	Point P;
	if (!DecodePoint(P, str, str.size()))
		BERDecodeError();
	return P;
}

void EC2N::DEREncodePoint(BufferedTransformation &bt, const Point &P, bool compressed) const
{
	SecByteBlock str(EncodedPointSize(compressed));
	EncodePoint(str, P, compressed);
	DEREncodeOctetString(bt, str);
}

bool EC2N::ValidateParameters(RandomNumberGenerator &rng, unsigned int level) const
{
	bool pass = !!m_b;
	pass = pass && m_a.CoefficientCount() <= m_field->MaxElementBitLength();
	pass = pass && m_b.CoefficientCount() <= m_field->MaxElementBitLength();

	if (level >= 1)
		pass = pass && m_field->GetModulus().IsIrreducible();
		
	return pass;
}

bool EC2N::VerifyPoint(const Point &P) const
{
	const FieldElement &x = P.x, &y = P.y;
	return P.identity || 
		(x.CoefficientCount() <= m_field->MaxElementBitLength()
		&& y.CoefficientCount() <= m_field->MaxElementBitLength()
		&& !(((x+m_a)*x*x+m_b-(x+y)*y)%m_field->GetModulus()));
}

bool EC2N::Equal(const Point &P, const Point &Q) const
{
	if (P.identity && Q.identity)
		return true;

	if (P.identity && !Q.identity)
		return false;

	if (!P.identity && Q.identity)
		return false;

	return (m_field->Equal(P.x,Q.x) && m_field->Equal(P.y,Q.y));
}

const EC2N::Point& EC2N::Identity() const
{
	return Singleton<Point>().Ref();
}

const EC2N::Point& EC2N::Inverse(const Point &P) const
{
	if (P.identity)
		return P;
	else
	{
		m_R.identity = false;
		m_R.y = m_field->Add(P.x, P.y);
		m_R.x = P.x;
		return m_R;
	}
}

const EC2N::Point& EC2N::Add(const Point &P, const Point &Q) const
{
	if (P.identity) return Q;
	if (Q.identity) return P;
	if (Equal(P, Q)) return Double(P);
	if (m_field->Equal(P.x, Q.x) && m_field->Equal(P.y, m_field->Add(Q.x, Q.y))) return Identity();

	FieldElement t = m_field->Add(P.y, Q.y);
	t = m_field->Divide(t, m_field->Add(P.x, Q.x));
	FieldElement x = m_field->Square(t);
	m_field->Accumulate(x, t);
	m_field->Accumulate(x, Q.x);
	m_field->Accumulate(x, m_a);
	m_R.y = m_field->Add(P.y, m_field->Multiply(t, x));
	m_field->Accumulate(x, P.x);
	m_field->Accumulate(m_R.y, x);

	m_R.x.swap(x);
	m_R.identity = false;
	return m_R;
}

const EC2N::Point& EC2N::Double(const Point &P) const
{
	if (P.identity) return P;
	if (!m_field->IsUnit(P.x)) return Identity();

	FieldElement t = m_field->Divide(P.y, P.x);
	m_field->Accumulate(t, P.x);
	m_R.y = m_field->Square(P.x);
	m_R.x = m_field->Square(t);
	m_field->Accumulate(m_R.x, t);
	m_field->Accumulate(m_R.x, m_a);
	m_field->Accumulate(m_R.y, m_field->Multiply(t, m_R.x));
	m_field->Accumulate(m_R.y, m_R.x);

	m_R.identity = false;
	return m_R;
}

// ********************************************************

/*
EcPrecomputation<EC2N>& EcPrecomputation<EC2N>::operator=(const EcPrecomputation<EC2N> &rhs)
{
	m_ec = rhs.m_ec;
	m_ep = rhs.m_ep;
	m_ep.m_group = m_ec.get();
	return *this;
}

void EcPrecomputation<EC2N>::SetCurveAndBase(const EC2N &ec, const EC2N::Point &base)
{
	m_ec.reset(new EC2N(ec));
	m_ep.SetGroupAndBase(*m_ec, base);
}

void EcPrecomputation<EC2N>::Precompute(unsigned int maxExpBits, unsigned int storage)
{
	m_ep.Precompute(maxExpBits, storage);
}

void EcPrecomputation<EC2N>::Load(BufferedTransformation &bt)
{
	BERSequenceDecoder seq(bt);
	word32 version;
	BERDecodeUnsigned<word32>(seq, version, INTEGER, 1, 1);
	m_ep.m_exponentBase.BERDecode(seq);
	m_ep.m_windowSize = m_ep.m_exponentBase.BitCount() - 1;
	m_ep.m_bases.clear();
	while (!seq.EndReached())
		m_ep.m_bases.push_back(m_ec->BERDecodePoint(seq));
	seq.MessageEnd();
}

void EcPrecomputation<EC2N>::Save(BufferedTransformation &bt) const
{
	DERSequenceEncoder seq(bt);
	DEREncodeUnsigned<word32>(seq, 1);	// version
	m_ep.m_exponentBase.DEREncode(seq);
	for (unsigned i=0; i<m_ep.m_bases.size(); i++)
		m_ec->DEREncodePoint(seq, m_ep.m_bases[i]);
	seq.MessageEnd();
}

EC2N::Point EcPrecomputation<EC2N>::Exponentiate(const Integer &exponent) const
{
	return m_ep.Exponentiate(exponent);
}

EC2N::Point EcPrecomputation<EC2N>::CascadeExponentiate(const Integer &exponent, const DL_FixedBasePrecomputation<Element> &pc2, const Integer &exponent2) const
{
	return m_ep.CascadeExponentiate(exponent, static_cast<const EcPrecomputation<EC2N> &>(pc2).m_ep, exponent2);
}
*/

NAMESPACE_END

#endif

1 by weidai Initial revision	1	// ec2n.cpp - written and placed in the public domain by Wei Dai
	2
	3	#include "pch.h"
75 by weidai create DLL version, fix GetNextIV() bug in CTR and OFB modes	4
	5	#ifndef CRYPTOPP_IMPORTS
	6
1 by weidai Initial revision	7	#include "ec2n.h"
	8	#include "asn.h"
	9
	10	#include "algebra.cpp"
	11	#include "eprecomp.cpp"
	12
	13	NAMESPACE_BEGIN(CryptoPP)
	14
	15	EC2N::EC2N(BufferedTransformation &bt)
	16	: m_field(BERDecodeGF2NP(bt))
	17	{
	18	BERSequenceDecoder seq(bt);
	19	m_field->BERDecodeElement(seq, m_a);
	20	m_field->BERDecodeElement(seq, m_b);
	21	// skip optional seed
	22	if (!seq.EndReached())
	23	BERDecodeOctetString(seq, TheBitBucket());
	24	seq.MessageEnd();
	25	}
	26
	27	void EC2N::DEREncode(BufferedTransformation &bt) const
	28	{
	29	m_field->DEREncode(bt);
	30	DERSequenceEncoder seq(bt);
	31	m_field->DEREncodeElement(seq, m_a);
	32	m_field->DEREncodeElement(seq, m_b);
	33	seq.MessageEnd();
	34	}
	35
184 by weidai port to MSVC .NET 2005 beta 2	36	bool EC2N::DecodePoint(EC2N::Point &P, const byte *encodedPoint, size_t encodedPointLen) const
1 by weidai Initial revision	37	{
	38	StringStore store(encodedPoint, encodedPointLen);
	39	return DecodePoint(P, store, encodedPointLen);
	40	}
	41
184 by weidai port to MSVC .NET 2005 beta 2	42	bool EC2N::DecodePoint(EC2N::Point &P, BufferedTransformation &bt, size_t encodedPointLen) const
1 by weidai Initial revision	43	{
	44	byte type;
	45	if (encodedPointLen < 1 \|\| !bt.Get(type))
	46	return false;
	47
	48	switch (type)
	49	{
	50	case 0:
	51	P.identity = true;
	52	return true;
	53	case 2:
	54	case 3:
	55	{
	56	if (encodedPointLen != EncodedPointSize(true))
	57	return false;
	58
	59	P.identity = false;
	60	P.x.Decode(bt, m_field->MaxElementByteLength());
	61
	62	if (P.x.IsZero())
	63	{
	64	P.y = m_field->SquareRoot(m_b);
	65	return true;
	66	}
	67
	68	FieldElement z = m_field->Square(P.x);
	69	assert(P.x == m_field->SquareRoot(z));
	70	P.y = m_field->Divide(m_field->Add(m_field->Multiply(z, m_field->Add(P.x, m_a)), m_b), z);
	71	assert(P.x == m_field->Subtract(m_field->Divide(m_field->Subtract(m_field->Multiply(P.y, z), m_b), z), m_a));
	72	z = m_field->SolveQuadraticEquation(P.y);
	73	assert(m_field->Add(m_field->Square(z), z) == P.y);
	74	z.SetCoefficient(0, type & 1);
	75
	76	P.y = m_field->Multiply(z, P.x);
	77	return true;
	78	}
	79	case 4:
	80	{
	81	if (encodedPointLen != EncodedPointSize(false))
	82	return false;
	83
	84	unsigned int len = m_field->MaxElementByteLength();
	85	P.identity = false;
	86	P.x.Decode(bt, len);
	87	P.y.Decode(bt, len);
	88	return true;
	89	}
	90	default:
	91	return false;
	92	}
	93	}
	94
	95	void EC2N::EncodePoint(BufferedTransformation &bt, const Point &P, bool compressed) const
	96	{
	97	if (P.identity)
	98	NullStore().TransferTo(bt, EncodedPointSize(compressed));
	99	else if (compressed)
	100	{
	101	bt.Put(2 + (!P.x ? 0 : m_field->Divide(P.y, P.x).GetBit(0)));
	102	P.x.Encode(bt, m_field->MaxElementByteLength());
	103	}
	104	else
	105	{
	106	unsigned int len = m_field->MaxElementByteLength();
107	bt.Put(4); // uncompressed
108	P.x.Encode(bt, len);
109	P.y.Encode(bt, len);
110	}
111	}
112
113	void EC2N::EncodePoint(byte *encodedPoint, const Point &P, bool compressed) const
114	{
115	ArraySink sink(encodedPoint, EncodedPointSize(compressed));
116	EncodePoint(sink, P, compressed);
117	assert(sink.TotalPutLength() == EncodedPointSize(compressed));
118	}
119
120	EC2N::Point EC2N::BERDecodePoint(BufferedTransformation &bt) const
121	{
122	SecByteBlock str;
123	BERDecodeOctetString(bt, str);
124	Point P;
125	if (!DecodePoint(P, str, str.size()))
126	BERDecodeError();
127	return P;
128	}
129
130	void EC2N::DEREncodePoint(BufferedTransformation &bt, const Point &P, bool compressed) const
131	{
132	SecByteBlock str(EncodedPointSize(compressed));
133	EncodePoint(str, P, compressed);
134	DEREncodeOctetString(bt, str);
135	}
136
137	bool EC2N::ValidateParameters(RandomNumberGenerator &rng, unsigned int level) const
138	{
139	bool pass = !!m_b;
140	pass = pass && m_a.CoefficientCount() <= m_field->MaxElementBitLength();
141	pass = pass && m_b.CoefficientCount() <= m_field->MaxElementBitLength();
142
143	if (level >= 1)
144	pass = pass && m_field->GetModulus().IsIrreducible();
145
146	return pass;
147	}
148
149	bool EC2N::VerifyPoint(const Point &P) const
150	{
151	const FieldElement &x = P.x, &y = P.y;
152	return P.identity \|\|
153	(x.CoefficientCount() <= m_field->MaxElementBitLength()
154	&& y.CoefficientCount() <= m_field->MaxElementBitLength()
155	&& !(((x+m_a)xx+m_b-(x+y)*y)%m_field->GetModulus()));
156	}
157
158	bool EC2N::Equal(const Point &P, const Point &Q) const
159	{
160	if (P.identity && Q.identity)
161	return true;
162
163	if (P.identity && !Q.identity)
164	return false;
165
166	if (!P.identity && Q.identity)
167	return false;
168
169	return (m_field->Equal(P.x,Q.x) && m_field->Equal(P.y,Q.y));
170	}
171
172	const EC2N::Point& EC2N::Identity() const
173	{
106 by weidai fix potential threading problem with initialization of static objects	174	return Singleton<Point>().Ref();
1 by weidai Initial revision	175	}
	176
	177	const EC2N::Point& EC2N::Inverse(const Point &P) const
	178	{
	179	if (P.identity)
	180	return P;
	181	else
	182	{
	183	m_R.identity = false;
	184	m_R.y = m_field->Add(P.x, P.y);
	185	m_R.x = P.x;
	186	return m_R;
	187	}
	188	}
	189
	190	const EC2N::Point& EC2N::Add(const Point &P, const Point &Q) const
	191	{
	192	if (P.identity) return Q;
	193	if (Q.identity) return P;
	194	if (Equal(P, Q)) return Double(P);
	195	if (m_field->Equal(P.x, Q.x) && m_field->Equal(P.y, m_field->Add(Q.x, Q.y))) return Identity();
	196
	197	FieldElement t = m_field->Add(P.y, Q.y);
	198	t = m_field->Divide(t, m_field->Add(P.x, Q.x));
	199	FieldElement x = m_field->Square(t);
	200	m_field->Accumulate(x, t);
	201	m_field->Accumulate(x, Q.x);
	202	m_field->Accumulate(x, m_a);
	203	m_R.y = m_field->Add(P.y, m_field->Multiply(t, x));
	204	m_field->Accumulate(x, P.x);
	205	m_field->Accumulate(m_R.y, x);
	206
	207	m_R.x.swap(x);
	208	m_R.identity = false;
	209	return m_R;
	210	}
	211
	212	const EC2N::Point& EC2N::Double(const Point &P) const
	213	{
	214	if (P.identity) return P;
	215	if (!m_field->IsUnit(P.x)) return Identity();
	216
	217	FieldElement t = m_field->Divide(P.y, P.x);
	218	m_field->Accumulate(t, P.x);
	219	m_R.y = m_field->Square(P.x);
	220	m_R.x = m_field->Square(t);
	221	m_field->Accumulate(m_R.x, t);
	222	m_field->Accumulate(m_R.x, m_a);
	223	m_field->Accumulate(m_R.y, m_field->Multiply(t, m_R.x));
	224	m_field->Accumulate(m_R.y, m_R.x);
	225
	226	m_R.identity = false;
	227	return m_R;
	228	}
	229
	230	// ********************************************************
	231
	232	/*
	233	EcPrecomputation<EC2N>& EcPrecomputation<EC2N>::operator=(const EcPrecomputation<EC2N> &rhs)
	234	{
	235	m_ec = rhs.m_ec;
	236	m_ep = rhs.m_ep;
	237	m_ep.m_group = m_ec.get();
	238	return *this;
239	}
240
241	void EcPrecomputation<EC2N>::SetCurveAndBase(const EC2N &ec, const EC2N::Point &base)
242	{
243	m_ec.reset(new EC2N(ec));
244	m_ep.SetGroupAndBase(*m_ec, base);
245	}
246
247	void EcPrecomputation<EC2N>::Precompute(unsigned int maxExpBits, unsigned int storage)
248	{
249	m_ep.Precompute(maxExpBits, storage);
250	}
251
252	void EcPrecomputation<EC2N>::Load(BufferedTransformation &bt)
253	{
254	BERSequenceDecoder seq(bt);
255	word32 version;
256	BERDecodeUnsigned<word32>(seq, version, INTEGER, 1, 1);
257	m_ep.m_exponentBase.BERDecode(seq);
258	m_ep.m_windowSize = m_ep.m_exponentBase.BitCount() - 1;
259	m_ep.m_bases.clear();
260	while (!seq.EndReached())
261	m_ep.m_bases.push_back(m_ec->BERDecodePoint(seq));
262	seq.MessageEnd();
263	}
264
265	void EcPrecomputation<EC2N>::Save(BufferedTransformation &bt) const
266	{
267	DERSequenceEncoder seq(bt);
268	DEREncodeUnsigned<word32>(seq, 1); // version
269	m_ep.m_exponentBase.DEREncode(seq);
270	for (unsigned i=0; i<m_ep.m_bases.size(); i++)
271	m_ec->DEREncodePoint(seq, m_ep.m_bases[i]);
272	seq.MessageEnd();
273	}
274
275	EC2N::Point EcPrecomputation<EC2N>::Exponentiate(const Integer &exponent) const
276	{
277	return m_ep.Exponentiate(exponent);
278	}
279
280	EC2N::Point EcPrecomputation<EC2N>::CascadeExponentiate(const Integer &exponent, const DL_FixedBasePrecomputation<Element> &pc2, const Integer &exponent2) const
281	{
282	return m_ep.CascadeExponentiate(exponent, static_cast<const EcPrecomputation<EC2N> &>(pc2).m_ep, exponent2);
283	}
284	*/
285
286	NAMESPACE_END
75 by weidai create DLL version, fix GetNextIV() bug in CTR and OFB modes	287
	288	#endif