Crypto++ 8.5 Free C++ class library of cryptographic schemes

ec2n.cpp
1 // ec2n.cpp - originally written and placed in the public domain by Wei Dai
2
3 #include "pch.h"
4
5 #ifndef CRYPTOPP_IMPORTS
6
7 #include "ec2n.h"
8 #include "asn.h"
9 #include "integer.h"
10 #include "filters.h"
11 #include "algebra.cpp"
12 #include "eprecomp.cpp"
13
14 ANONYMOUS_NAMESPACE_BEGIN
15
16 using CryptoPP::EC2N;
17
18 #if defined(HAVE_GCC_INIT_PRIORITY)
19 #define INIT_ATTRIBUTE __attribute__ ((init_priority (CRYPTOPP_INIT_PRIORITY + 51)))
20 const EC2N::Point g_identity INIT_ATTRIBUTE = EC2N::Point();
21 #elif defined(HAVE_MSC_INIT_PRIORITY)
22 #pragma warning(disable: 4075)
23 #pragma init_seg(".CRT$XCU")
24 const EC2N::Point g_identity;
25 #pragma warning(default: 4075)
26 #elif defined(HAVE_XLC_INIT_PRIORITY)
27 #pragma priority(290)
28 const EC2N::Point g_identity;
29 #endif
30
31 ANONYMOUS_NAMESPACE_END
32
33 NAMESPACE_BEGIN(CryptoPP)
34
35 EC2N::EC2N(BufferedTransformation &bt)
36 : m_field(BERDecodeGF2NP(bt))
37 {
38 BERSequenceDecoder seq(bt);
39 m_field->BERDecodeElement(seq, m_a);
40 m_field->BERDecodeElement(seq, m_b);
41 // skip optional seed
42 if (!seq.EndReached())
43 {
44 SecByteBlock seed;
45 unsigned int unused;
46 BERDecodeBitString(seq, seed, unused);
47 }
48 seq.MessageEnd();
49 }
50
51 void EC2N::DEREncode(BufferedTransformation &bt) const
52 {
53 m_field->DEREncode(bt);
54 DERSequenceEncoder seq(bt);
55 m_field->DEREncodeElement(seq, m_a);
56 m_field->DEREncodeElement(seq, m_b);
57 seq.MessageEnd();
58 }
59
60 bool EC2N::DecodePoint(EC2N::Point &P, const byte *encodedPoint, size_t encodedPointLen) const
61 {
62 StringStore store(encodedPoint, encodedPointLen);
63 return DecodePoint(P, store, encodedPointLen);
64 }
65
66 bool EC2N::DecodePoint(EC2N::Point &P, BufferedTransformation &bt, size_t encodedPointLen) const
67 {
68 byte type;
69 if (encodedPointLen < 1 || !bt.Get(type))
70 return false;
71
72 switch (type)
73 {
74 case 0:
75 P.identity = true;
76 return true;
77 case 2:
78 case 3:
79 {
80 if (encodedPointLen != EncodedPointSize(true))
81 return false;
82
83 P.identity = false;
84 P.x.Decode(bt, m_field->MaxElementByteLength());
85
86 if (P.x.IsZero())
87 {
88 P.y = m_field->SquareRoot(m_b);
89 return true;
90 }
91
92 FieldElement z = m_field->Square(P.x);
93 CRYPTOPP_ASSERT(P.x == m_field->SquareRoot(z));
94 P.y = m_field->Divide(m_field->Add(m_field->Multiply(z, m_field->Add(P.x, m_a)), m_b), z);
95 CRYPTOPP_ASSERT(P.x == m_field->Subtract(m_field->Divide(m_field->Subtract(m_field->Multiply(P.y, z), m_b), z), m_a));
96 z = m_field->SolveQuadraticEquation(P.y);
97 CRYPTOPP_ASSERT(m_field->Add(m_field->Square(z), z) == P.y);
98 z.SetCoefficient(0, type & 1);
99
100 P.y = m_field->Multiply(z, P.x);
101 return true;
102 }
103 case 4:
104 {
105 if (encodedPointLen != EncodedPointSize(false))
106 return false;
107
108 unsigned int len = m_field->MaxElementByteLength();
109 P.identity = false;
110 P.x.Decode(bt, len);
111 P.y.Decode(bt, len);
112 return true;
113 }
114 default:
115 return false;
116 }
117 }
118
119 void EC2N::EncodePoint(BufferedTransformation &bt, const Point &P, bool compressed) const
120 {
121 if (P.identity)
122 NullStore().TransferTo(bt, EncodedPointSize(compressed));
123 else if (compressed)
124 {
125 bt.Put((byte)(2U + (!P.x ? 0U : m_field->Divide(P.y, P.x).GetBit(0))));
126 P.x.Encode(bt, m_field->MaxElementByteLength());
127 }
128 else
129 {
130 unsigned int len = m_field->MaxElementByteLength();
131 bt.Put(4); // uncompressed
132 P.x.Encode(bt, len);
133 P.y.Encode(bt, len);
134 }
135 }
136
137 void EC2N::EncodePoint(byte *encodedPoint, const Point &P, bool compressed) const
138 {
139 ArraySink sink(encodedPoint, EncodedPointSize(compressed));
140 EncodePoint(sink, P, compressed);
141 CRYPTOPP_ASSERT(sink.TotalPutLength() == EncodedPointSize(compressed));
142 }
143
144 EC2N::Point EC2N::BERDecodePoint(BufferedTransformation &bt) const
145 {
146 SecByteBlock str;
147 BERDecodeOctetString(bt, str);
148 Point P;
149 if (!DecodePoint(P, str, str.size()))
150 BERDecodeError();
151 return P;
152 }
153
154 void EC2N::DEREncodePoint(BufferedTransformation &bt, const Point &P, bool compressed) const
155 {
156 SecByteBlock str(EncodedPointSize(compressed));
157 EncodePoint(str, P, compressed);
158 DEREncodeOctetString(bt, str);
159 }
160
161 bool EC2N::ValidateParameters(RandomNumberGenerator &rng, unsigned int level) const
162 {
163 CRYPTOPP_UNUSED(rng);
164 bool pass = !!m_b;
165 pass = pass && m_a.CoefficientCount() <= m_field->MaxElementBitLength();
166 pass = pass && m_b.CoefficientCount() <= m_field->MaxElementBitLength();
167
168 if (level >= 1)
169 pass = pass && m_field->GetModulus().IsIrreducible();
170
171 return pass;
172 }
173
174 bool EC2N::VerifyPoint(const Point &P) const
175 {
176 const FieldElement &x = P.x, &y = P.y;
177 return P.identity ||
178 (x.CoefficientCount() <= m_field->MaxElementBitLength()
179 && y.CoefficientCount() <= m_field->MaxElementBitLength()
180 && !(((x+m_a)*x*x+m_b-(x+y)*y)%m_field->GetModulus()));
181 }
182
183 bool EC2N::Equal(const Point &P, const Point &Q) const
184 {
185 if (P.identity && Q.identity)
186 return true;
187
188 if (P.identity && !Q.identity)
189 return false;
190
191 if (!P.identity && Q.identity)
192 return false;
193
194 return (m_field->Equal(P.x,Q.x) && m_field->Equal(P.y,Q.y));
195 }
196
197 const EC2N::Point& EC2N::Identity() const
198 {
199 #if defined(HAVE_GCC_INIT_PRIORITY) || defined(HAVE_MSC_INIT_PRIORITY) || defined(HAVE_XLC_INIT_PRIORITY)
200 return g_identity;
201 #elif defined(CRYPTOPP_CXX11_STATIC_INIT)
202 static const EC2N::Point g_identity;
203 return g_identity;
204 #else
205 return Singleton<Point>().Ref();
206 #endif
207 }
208
209 const EC2N::Point& EC2N::Inverse(const Point &P) const
210 {
211 if (P.identity)
212 return P;
213 else
214 {
215 m_R.identity = false;
216 m_R.y = m_field->Add(P.x, P.y);
217 m_R.x = P.x;
218 return m_R;
219 }
220 }
221
222 const EC2N::Point& EC2N::Add(const Point &P, const Point &Q) const
223 {
224 if (P.identity) return Q;
225 if (Q.identity) return P;
226 if (Equal(P, Q)) return Double(P);
227 if (m_field->Equal(P.x, Q.x) && m_field->Equal(P.y, m_field->Add(Q.x, Q.y))) return Identity();
228
229 FieldElement t = m_field->Add(P.y, Q.y);
230 t = m_field->Divide(t, m_field->Add(P.x, Q.x));
231 FieldElement x = m_field->Square(t);
232 m_field->Accumulate(x, t);
233 m_field->Accumulate(x, Q.x);
234 m_field->Accumulate(x, m_a);
235 m_R.y = m_field->Add(P.y, m_field->Multiply(t, x));
236 m_field->Accumulate(x, P.x);
237 m_field->Accumulate(m_R.y, x);
238
239 m_R.x.swap(x);
240 m_R.identity = false;
241 return m_R;
242 }
243
244 const EC2N::Point& EC2N::Double(const Point &P) const
245 {
246 if (P.identity) return P;
247 if (!m_field->IsUnit(P.x)) return Identity();
248
249 FieldElement t = m_field->Divide(P.y, P.x);
250 m_field->Accumulate(t, P.x);
251 m_R.y = m_field->Square(P.x);
252 m_R.x = m_field->Square(t);
253 m_field->Accumulate(m_R.x, t);
254 m_field->Accumulate(m_R.x, m_a);
255 m_field->Accumulate(m_R.y, m_field->Multiply(t, m_R.x));
256 m_field->Accumulate(m_R.y, m_R.x);
257
258 m_R.identity = false;
259 return m_R;
260 }
261
262 // ********************************************************
263
264 #if 0
265 EcPrecomputation<EC2N>& EcPrecomputation<EC2N>::operator=(const EcPrecomputation<EC2N> &rhs)
266 {
267 m_ec = rhs.m_ec;
268 m_ep = rhs.m_ep;
269 m_ep.m_group = m_ec.get();
270 return *this;
271 }
272
273 void EcPrecomputation<EC2N>::SetCurveAndBase(const EC2N &ec, const EC2N::Point &base)
274 {
275 m_ec.reset(new EC2N(ec));
276 m_ep.SetGroupAndBase(*m_ec, base);
277 }
278
279 void EcPrecomputation<EC2N>::Precompute(unsigned int maxExpBits, unsigned int storage)
280 {
281 m_ep.Precompute(maxExpBits, storage);
282 }
283
284 void EcPrecomputation<EC2N>::Load(BufferedTransformation &bt)
285 {
286 BERSequenceDecoder seq(bt);
287 word32 version;
288 BERDecodeUnsigned<word32>(seq, version, INTEGER, 1, 1);
289 m_ep.m_exponentBase.BERDecode(seq);
290 m_ep.m_windowSize = m_ep.m_exponentBase.BitCount() - 1;
291 m_ep.m_bases.clear();
292 while (!seq.EndReached())
293 m_ep.m_bases.push_back(m_ec->BERDecodePoint(seq));
294 seq.MessageEnd();
295 }
296
297 void EcPrecomputation<EC2N>::Save(BufferedTransformation &bt) const
298 {
299 DERSequenceEncoder seq(bt);
300 DEREncodeUnsigned<word32>(seq, 1); // version
301 m_ep.m_exponentBase.DEREncode(seq);
302 for (unsigned i=0; i<m_ep.m_bases.size(); i++)
303 m_ec->DEREncodePoint(seq, m_ep.m_bases[i]);
304 seq.MessageEnd();
305 }
306
307 EC2N::Point EcPrecomputation<EC2N>::Exponentiate(const Integer &exponent) const
308 {
309 return m_ep.Exponentiate(exponent);
310 }
311
312 EC2N::Point EcPrecomputation<EC2N>::CascadeExponentiate(const Integer &exponent, const DL_FixedBasePrecomputation<Element> &pc2, const Integer &exponent2) const
313 {
314 return m_ep.CascadeExponentiate(exponent, static_cast<const EcPrecomputation<EC2N> &>(pc2).m_ep, exponent2);
315 }
316 #endif
317
318 NAMESPACE_END
319
320 #endif
EC2N::BERDecodePoint
Point BERDecodePoint(BufferedTransformation &bt) const
BER Decodes an elliptic curve point.
Singleton::Ref
const T & Ref(...) const
Return a reference to the inner Singleton object.
Definition: misc.h:325
EC2N::Equal
bool Equal(const Point &P, const Point &Q) const
Compare two elements for equality.
StringStore
String-based implementation of Store interface.
Definition: filters.h:1258
EC2N::Double
const Point & Double(const Point &P) const
Doubles an element in the group.
DERSequenceEncoder
DER Sequence Encoder.
Definition: asn.h:556
BufferedTransformation
Interface for buffered transformations.
Definition: cryptlib.h:1634
EC2N::EncodePoint
void EncodePoint(byte *encodedPoint, const Point &P, bool compressed) const
Encodes an elliptic curve point.
EC2N
Elliptic Curve over GF(2^n)
Definition: ec2n.h:26
DL_FixedBasePrecomputation
DL_FixedBasePrecomputation interface.
Definition: eprecomp.h:60
SecByteBlock
SecBlock<byte> typedef.
Definition: secblock.h:1115
EC2N::Inverse
const Point & Inverse(const Point &P) const
Inverts the element in the group.
CRYPTOPP_ASSERT
#define CRYPTOPP_ASSERT(exp)
Debugging and diagnostic assertion.
Definition: trap.h:68
BufferedTransformation::Put
size_t Put(byte inByte, bool blocking=true)
Input a byte for processing.
Definition: cryptlib.h:1656
BufferedTransformation::Get
virtual size_t Get(byte &outByte)
Retrieve a 8-bit byte.
Singleton
Restricts the instantiation of a class to one static object without locks.
Definition: misc.h:304
EC2NPoint
Elliptical Curve Point over GF(2^n)
Definition: ecpoint.h:53
pch.h
Precompiled header file.
word32
unsigned int word32
32-bit unsigned datatype
Definition: config_int.h:62
filters.h
Implementation of BufferedTransformation's attachment interface.
EC2N::VerifyPoint
bool VerifyPoint(const Point &P) const
Verifies points on elliptic curve.
RandomNumberGenerator
Interface for random number generators.
Definition: cryptlib.h:1417
BERDecodeError
void BERDecodeError()
Raises a BERDecodeErr.
Definition: asn.h:104
BERDecodeBitString
CRYPTOPP_DLL size_t BERDecodeBitString(BufferedTransformation &bt, SecByteBlock &str, unsigned int &unusedBits)
DER decode bit string.
EC2N::DecodePoint
bool DecodePoint(Point &P, BufferedTransformation &bt, size_t len) const
Decodes an elliptic curve point.
EC2N::Add
const Point & Add(const Point &P, const Point &Q) const
Adds elements in the group.
EcPrecomputation
Elliptic Curve precomputation.
Definition: ec2n.h:99
ArraySink
Copy input to a memory buffer.
Definition: filters.h:1199
EC2N::DEREncode
void DEREncode(BufferedTransformation &bt) const
Encode the fields fieldID and curve of the sequence ECParameters.
NullStore
Empty store.
Definition: filters.h:1320
EC2N::EC2N
EC2N()
Construct an EC2N.
Definition: ec2n.h:36
asn.h
Classes and functions for working with ANS.1 objects.
BufferedTransformation::TransferTo
lword TransferTo(BufferedTransformation &target, lword transferMax=LWORD_MAX, const std::string &channel=DEFAULT_CHANNEL)
move transferMax bytes of the buffered output to target as input
Definition: cryptlib.h:1974
EcPrecomputation< EC2N >
EC2N precomputation specialization.
Definition: ec2n.h:104
DEREncodeOctetString
CRYPTOPP_DLL size_t DEREncodeOctetString(BufferedTransformation &bt, const byte *str, size_t strLen)
DER encode octet string.
SecBlock::size
size_type size() const
Provides the count of elements in the SecBlock.
Definition: secblock.h:849
EC2N::DEREncodePoint
void DEREncodePoint(BufferedTransformation &bt, const Point &P, bool compressed) const
DER Encodes an elliptic curve point.
CryptoPP
Crypto++ library namespace.
BERDecodeOctetString
CRYPTOPP_DLL size_t BERDecodeOctetString(BufferedTransformation &bt, SecByteBlock &str)
BER decode octet string.
EC2N::EncodedPointSize
unsigned int EncodedPointSize(bool compressed=false) const
Determines encoded point size.
Definition: ec2n.h:69
ec2n.h
Classes for Elliptic Curves over binary fields.
integer.h
Multiple precision integer with arithmetic operations.
Integer
Multiple precision integer with arithmetic operations.
Definition: integer.h:49
BERSequenceDecoder
BER Sequence Decoder.
Definition: asn.h:524
INTEGER
@ INTEGER
ASN.1 Integer.
Definition: asn.h:34