diff options
Diffstat (limited to 'plugins/CryptoPP/crypto/src/gf2n.cpp')
| -rw-r--r-- | plugins/CryptoPP/crypto/src/gf2n.cpp | 879 |
1 files changed, 879 insertions, 0 deletions
diff --git a/plugins/CryptoPP/crypto/src/gf2n.cpp b/plugins/CryptoPP/crypto/src/gf2n.cpp new file mode 100644 index 0000000000..463db0fa3b --- /dev/null +++ b/plugins/CryptoPP/crypto/src/gf2n.cpp @@ -0,0 +1,879 @@ +// gf2n.cpp - written and placed in the public domain by Wei Dai
+
+#include "pch.h"
+
+#ifndef CRYPTOPP_IMPORTS
+
+#include "gf2n.h"
+#include "algebra.h"
+#include "words.h"
+#include "randpool.h"
+#include "asn.h"
+#include "oids.h"
+
+#include <iostream>
+
+NAMESPACE_BEGIN(CryptoPP)
+
+PolynomialMod2::PolynomialMod2()
+{
+}
+
+PolynomialMod2::PolynomialMod2(word value, size_t bitLength)
+ : reg(BitsToWords(bitLength))
+{
+ assert(value==0 || reg.size()>0);
+
+ if (reg.size() > 0)
+ {
+ reg[0] = value;
+ SetWords(reg+1, 0, reg.size()-1);
+ }
+}
+
+PolynomialMod2::PolynomialMod2(const PolynomialMod2& t)
+ : reg(t.reg.size())
+{
+ CopyWords(reg, t.reg, reg.size());
+}
+
+void PolynomialMod2::Randomize(RandomNumberGenerator &rng, size_t nbits)
+{
+ const size_t nbytes = nbits/8 + 1;
+ SecByteBlock buf(nbytes);
+ rng.GenerateBlock(buf, nbytes);
+ buf[0] = (byte)Crop(buf[0], nbits % 8);
+ Decode(buf, nbytes);
+}
+
+PolynomialMod2 PolynomialMod2::AllOnes(size_t bitLength)
+{
+ PolynomialMod2 result((word)0, bitLength);
+ SetWords(result.reg, ~(word)0, result.reg.size());
+ if (bitLength%WORD_BITS)
+ result.reg[result.reg.size()-1] = (word)Crop(result.reg[result.reg.size()-1], bitLength%WORD_BITS);
+ return result;
+}
+
+void PolynomialMod2::SetBit(size_t n, int value)
+{
+ if (value)
+ {
+ reg.CleanGrow(n/WORD_BITS + 1);
+ reg[n/WORD_BITS] |= (word(1) << (n%WORD_BITS));
+ }
+ else
+ {
+ if (n/WORD_BITS < reg.size())
+ reg[n/WORD_BITS] &= ~(word(1) << (n%WORD_BITS));
+ }
+}
+
+byte PolynomialMod2::GetByte(size_t n) const
+{
+ if (n/WORD_SIZE >= reg.size())
+ return 0;
+ else
+ return byte(reg[n/WORD_SIZE] >> ((n%WORD_SIZE)*8));
+}
+
+void PolynomialMod2::SetByte(size_t n, byte value)
+{
+ reg.CleanGrow(BytesToWords(n+1));
+ reg[n/WORD_SIZE] &= ~(word(0xff) << 8*(n%WORD_SIZE));
+ reg[n/WORD_SIZE] |= (word(value) << 8*(n%WORD_SIZE));
+}
+
+PolynomialMod2 PolynomialMod2::Monomial(size_t i)
+{
+ PolynomialMod2 r((word)0, i+1);
+ r.SetBit(i);
+ return r;
+}
+
+PolynomialMod2 PolynomialMod2::Trinomial(size_t t0, size_t t1, size_t t2)
+{
+ PolynomialMod2 r((word)0, t0+1);
+ r.SetBit(t0);
+ r.SetBit(t1);
+ r.SetBit(t2);
+ return r;
+}
+
+PolynomialMod2 PolynomialMod2::Pentanomial(size_t t0, size_t t1, size_t t2, size_t t3, size_t t4)
+{
+ PolynomialMod2 r((word)0, t0+1);
+ r.SetBit(t0);
+ r.SetBit(t1);
+ r.SetBit(t2);
+ r.SetBit(t3);
+ r.SetBit(t4);
+ return r;
+}
+
+template <word i>
+struct NewPolynomialMod2
+{
+ PolynomialMod2 * operator()() const
+ {
+ return new PolynomialMod2(i);
+ }
+};
+
+const PolynomialMod2 &PolynomialMod2::Zero()
+{
+ return Singleton<PolynomialMod2>().Ref();
+}
+
+const PolynomialMod2 &PolynomialMod2::One()
+{
+ return Singleton<PolynomialMod2, NewPolynomialMod2<1> >().Ref();
+}
+
+void PolynomialMod2::Decode(const byte *input, size_t inputLen)
+{
+ StringStore store(input, inputLen);
+ Decode(store, inputLen);
+}
+
+void PolynomialMod2::Encode(byte *output, size_t outputLen) const
+{
+ ArraySink sink(output, outputLen);
+ Encode(sink, outputLen);
+}
+
+void PolynomialMod2::Decode(BufferedTransformation &bt, size_t inputLen)
+{
+ reg.CleanNew(BytesToWords(inputLen));
+
+ for (size_t i=inputLen; i > 0; i--)
+ {
+ byte b;
+ bt.Get(b);
+ reg[(i-1)/WORD_SIZE] |= word(b) << ((i-1)%WORD_SIZE)*8;
+ }
+}
+
+void PolynomialMod2::Encode(BufferedTransformation &bt, size_t outputLen) const
+{
+ for (size_t i=outputLen; i > 0; i--)
+ bt.Put(GetByte(i-1));
+}
+
+void PolynomialMod2::DEREncodeAsOctetString(BufferedTransformation &bt, size_t length) const
+{
+ DERGeneralEncoder enc(bt, OCTET_STRING);
+ Encode(enc, length);
+ enc.MessageEnd();
+}
+
+void PolynomialMod2::BERDecodeAsOctetString(BufferedTransformation &bt, size_t length)
+{
+ BERGeneralDecoder dec(bt, OCTET_STRING);
+ if (!dec.IsDefiniteLength() || dec.RemainingLength() != length)
+ BERDecodeError();
+ Decode(dec, length);
+ dec.MessageEnd();
+}
+
+unsigned int PolynomialMod2::WordCount() const
+{
+ return (unsigned int)CountWords(reg, reg.size());
+}
+
+unsigned int PolynomialMod2::ByteCount() const
+{
+ unsigned wordCount = WordCount();
+ if (wordCount)
+ return (wordCount-1)*WORD_SIZE + BytePrecision(reg[wordCount-1]);
+ else
+ return 0;
+}
+
+unsigned int PolynomialMod2::BitCount() const
+{
+ unsigned wordCount = WordCount();
+ if (wordCount)
+ return (wordCount-1)*WORD_BITS + BitPrecision(reg[wordCount-1]);
+ else
+ return 0;
+}
+
+unsigned int PolynomialMod2::Parity() const
+{
+ unsigned i;
+ word temp=0;
+ for (i=0; i<reg.size(); i++)
+ temp ^= reg[i];
+ return CryptoPP::Parity(temp);
+}
+
+PolynomialMod2& PolynomialMod2::operator=(const PolynomialMod2& t)
+{
+ reg.Assign(t.reg);
+ return *this;
+}
+
+PolynomialMod2& PolynomialMod2::operator^=(const PolynomialMod2& t)
+{
+ reg.CleanGrow(t.reg.size());
+ XorWords(reg, t.reg, t.reg.size());
+ return *this;
+}
+
+PolynomialMod2 PolynomialMod2::Xor(const PolynomialMod2 &b) const
+{
+ if (b.reg.size() >= reg.size())
+ {
+ PolynomialMod2 result((word)0, b.reg.size()*WORD_BITS);
+ XorWords(result.reg, reg, b.reg, reg.size());
+ CopyWords(result.reg+reg.size(), b.reg+reg.size(), b.reg.size()-reg.size());
+ return result;
+ }
+ else
+ {
+ PolynomialMod2 result((word)0, reg.size()*WORD_BITS);
+ XorWords(result.reg, reg, b.reg, b.reg.size());
+ CopyWords(result.reg+b.reg.size(), reg+b.reg.size(), reg.size()-b.reg.size());
+ return result;
+ }
+}
+
+PolynomialMod2 PolynomialMod2::And(const PolynomialMod2 &b) const
+{
+ PolynomialMod2 result((word)0, WORD_BITS*STDMIN(reg.size(), b.reg.size()));
+ AndWords(result.reg, reg, b.reg, result.reg.size());
+ return result;
+}
+
+PolynomialMod2 PolynomialMod2::Times(const PolynomialMod2 &b) const
+{
+ PolynomialMod2 result((word)0, BitCount() + b.BitCount());
+
+ for (int i=b.Degree(); i>=0; i--)
+ {
+ result <<= 1;
+ if (b[i])
+ XorWords(result.reg, reg, reg.size());
+ }
+ return result;
+}
+
+PolynomialMod2 PolynomialMod2::Squared() const
+{
+ static const word map[16] = {0, 1, 4, 5, 16, 17, 20, 21, 64, 65, 68, 69, 80, 81, 84, 85};
+
+ PolynomialMod2 result((word)0, 2*reg.size()*WORD_BITS);
+
+ for (unsigned i=0; i<reg.size(); i++)
+ {
+ unsigned j;
+
+ for (j=0; j<WORD_BITS; j+=8)
+ result.reg[2*i] |= map[(reg[i] >> (j/2)) % 16] << j;
+
+ for (j=0; j<WORD_BITS; j+=8)
+ result.reg[2*i+1] |= map[(reg[i] >> (j/2 + WORD_BITS/2)) % 16] << j;
+ }
+
+ return result;
+}
+
+void PolynomialMod2::Divide(PolynomialMod2 &remainder, PolynomialMod2 "ient,
+ const PolynomialMod2 ÷nd, const PolynomialMod2 &divisor)
+{
+ if (!divisor)
+ throw PolynomialMod2::DivideByZero();
+
+ int degree = divisor.Degree();
+ remainder.reg.CleanNew(BitsToWords(degree+1));
+ if (dividend.BitCount() >= divisor.BitCount())
+ quotient.reg.CleanNew(BitsToWords(dividend.BitCount() - divisor.BitCount() + 1));
+ else
+ quotient.reg.CleanNew(0);
+
+ for (int i=dividend.Degree(); i>=0; i--)
+ {
+ remainder <<= 1;
+ remainder.reg[0] |= dividend[i];
+ if (remainder[degree])
+ {
+ remainder -= divisor;
+ quotient.SetBit(i);
+ }
+ }
+}
+
+PolynomialMod2 PolynomialMod2::DividedBy(const PolynomialMod2 &b) const
+{
+ PolynomialMod2 remainder, quotient;
+ PolynomialMod2::Divide(remainder, quotient, *this, b);
+ return quotient;
+}
+
+PolynomialMod2 PolynomialMod2::Modulo(const PolynomialMod2 &b) const
+{
+ PolynomialMod2 remainder, quotient;
+ PolynomialMod2::Divide(remainder, quotient, *this, b);
+ return remainder;
+}
+
+PolynomialMod2& PolynomialMod2::operator<<=(unsigned int n)
+{
+ if (!reg.size())
+ return *this;
+
+ int i;
+ word u;
+ word carry=0;
+ word *r=reg;
+
+ if (n==1) // special case code for most frequent case
+ {
+ i = (int)reg.size();
+ while (i--)
+ {
+ u = *r;
+ *r = (u << 1) | carry;
+ carry = u >> (WORD_BITS-1);
+ r++;
+ }
+
+ if (carry)
+ {
+ reg.Grow(reg.size()+1);
+ reg[reg.size()-1] = carry;
+ }
+
+ return *this;
+ }
+
+ int shiftWords = n / WORD_BITS;
+ int shiftBits = n % WORD_BITS;
+
+ if (shiftBits)
+ {
+ i = (int)reg.size();
+ while (i--)
+ {
+ u = *r;
+ *r = (u << shiftBits) | carry;
+ carry = u >> (WORD_BITS-shiftBits);
+ r++;
+ }
+ }
+
+ if (carry)
+ {
+ reg.Grow(reg.size()+shiftWords+1);
+ reg[reg.size()-1] = carry;
+ }
+ else
+ reg.Grow(reg.size()+shiftWords);
+
+ if (shiftWords)
+ {
+ for (i = (int)reg.size()-1; i>=shiftWords; i--)
+ reg[i] = reg[i-shiftWords];
+ for (; i>=0; i--)
+ reg[i] = 0;
+ }
+
+ return *this;
+}
+
+PolynomialMod2& PolynomialMod2::operator>>=(unsigned int n)
+{
+ if (!reg.size())
+ return *this;
+
+ int shiftWords = n / WORD_BITS;
+ int shiftBits = n % WORD_BITS;
+
+ size_t i;
+ word u;
+ word carry=0;
+ word *r=reg+reg.size()-1;
+
+ if (shiftBits)
+ {
+ i = reg.size();
+ while (i--)
+ {
+ u = *r;
+ *r = (u >> shiftBits) | carry;
+ carry = u << (WORD_BITS-shiftBits);
+ r--;
+ }
+ }
+
+ if (shiftWords)
+ {
+ for (i=0; i<reg.size()-shiftWords; i++)
+ reg[i] = reg[i+shiftWords];
+ for (; i<reg.size(); i++)
+ reg[i] = 0;
+ }
+
+ return *this;
+}
+
+PolynomialMod2 PolynomialMod2::operator<<(unsigned int n) const
+{
+ PolynomialMod2 result(*this);
+ return result<<=n;
+}
+
+PolynomialMod2 PolynomialMod2::operator>>(unsigned int n) const
+{
+ PolynomialMod2 result(*this);
+ return result>>=n;
+}
+
+bool PolynomialMod2::operator!() const
+{
+ for (unsigned i=0; i<reg.size(); i++)
+ if (reg[i]) return false;
+ return true;
+}
+
+bool PolynomialMod2::Equals(const PolynomialMod2 &rhs) const
+{
+ size_t i, smallerSize = STDMIN(reg.size(), rhs.reg.size());
+
+ for (i=0; i<smallerSize; i++)
+ if (reg[i] != rhs.reg[i]) return false;
+
+ for (i=smallerSize; i<reg.size(); i++)
+ if (reg[i] != 0) return false;
+
+ for (i=smallerSize; i<rhs.reg.size(); i++)
+ if (rhs.reg[i] != 0) return false;
+
+ return true;
+}
+
+std::ostream& operator<<(std::ostream& out, const PolynomialMod2 &a)
+{
+ // Get relevant conversion specifications from ostream.
+ long f = out.flags() & std::ios::basefield; // Get base digits.
+ int bits, block;
+ char suffix;
+ switch(f)
+ {
+ case std::ios::oct :
+ bits = 3;
+ block = 4;
+ suffix = 'o';
+ break;
+ case std::ios::hex :
+ bits = 4;
+ block = 2;
+ suffix = 'h';
+ break;
+ default :
+ bits = 1;
+ block = 8;
+ suffix = 'b';
+ }
+
+ if (!a)
+ return out << '0' << suffix;
+
+ SecBlock<char> s(a.BitCount()/bits+1);
+ unsigned i;
+ const char vec[]="0123456789ABCDEF";
+
+ for (i=0; i*bits < a.BitCount(); i++)
+ {
+ int digit=0;
+ for (int j=0; j<bits; j++)
+ digit |= a[i*bits+j] << j;
+ s[i]=vec[digit];
+ }
+
+ while (i--)
+ {
+ out << s[i];
+ if (i && (i%block)==0)
+ out << ',';
+ }
+
+ return out << suffix;
+}
+
+PolynomialMod2 PolynomialMod2::Gcd(const PolynomialMod2 &a, const PolynomialMod2 &b)
+{
+ return EuclideanDomainOf<PolynomialMod2>().Gcd(a, b);
+}
+
+PolynomialMod2 PolynomialMod2::InverseMod(const PolynomialMod2 &modulus) const
+{
+ typedef EuclideanDomainOf<PolynomialMod2> Domain;
+ return QuotientRing<Domain>(Domain(), modulus).MultiplicativeInverse(*this);
+}
+
+bool PolynomialMod2::IsIrreducible() const
+{
+ signed int d = Degree();
+ if (d <= 0)
+ return false;
+
+ PolynomialMod2 t(2), u(t);
+ for (int i=1; i<=d/2; i++)
+ {
+ u = u.Squared()%(*this);
+ if (!Gcd(u+t, *this).IsUnit())
+ return false;
+ }
+ return true;
+}
+
+// ********************************************************
+
+GF2NP::GF2NP(const PolynomialMod2 &modulus)
+ : QuotientRing<EuclideanDomainOf<PolynomialMod2> >(EuclideanDomainOf<PolynomialMod2>(), modulus), m(modulus.Degree())
+{
+}
+
+GF2NP::Element GF2NP::SquareRoot(const Element &a) const
+{
+ Element r = a;
+ for (unsigned int i=1; i<m; i++)
+ r = Square(r);
+ return r;
+}
+
+GF2NP::Element GF2NP::HalfTrace(const Element &a) const
+{
+ assert(m%2 == 1);
+ Element h = a;
+ for (unsigned int i=1; i<=(m-1)/2; i++)
+ h = Add(Square(Square(h)), a);
+ return h;
+}
+
+GF2NP::Element GF2NP::SolveQuadraticEquation(const Element &a) const
+{
+ if (m%2 == 0)
+ {
+ Element z, w;
+ RandomPool rng;
+ do
+ {
+ Element p((RandomNumberGenerator &)rng, m);
+ z = PolynomialMod2::Zero();
+ w = p;
+ for (unsigned int i=1; i<=m-1; i++)
+ {
+ w = Square(w);
+ z = Square(z);
+ Accumulate(z, Multiply(w, a));
+ Accumulate(w, p);
+ }
+ } while (w.IsZero());
+ return z;
+ }
+ else
+ return HalfTrace(a);
+}
+
+// ********************************************************
+
+GF2NT::GF2NT(unsigned int t0, unsigned int t1, unsigned int t2)
+ : GF2NP(PolynomialMod2::Trinomial(t0, t1, t2))
+ , t0(t0), t1(t1)
+ , result((word)0, m)
+{
+ assert(t0 > t1 && t1 > t2 && t2==0);
+}
+
+const GF2NT::Element& GF2NT::MultiplicativeInverse(const Element &a) const
+{
+ if (t0-t1 < WORD_BITS)
+ return GF2NP::MultiplicativeInverse(a);
+
+ SecWordBlock T(m_modulus.reg.size() * 4);
+ word *b = T;
+ word *c = T+m_modulus.reg.size();
+ word *f = T+2*m_modulus.reg.size();
+ word *g = T+3*m_modulus.reg.size();
+ size_t bcLen=1, fgLen=m_modulus.reg.size();
+ unsigned int k=0;
+
+ SetWords(T, 0, 3*m_modulus.reg.size());
+ b[0]=1;
+ assert(a.reg.size() <= m_modulus.reg.size());
+ CopyWords(f, a.reg, a.reg.size());
+ CopyWords(g, m_modulus.reg, m_modulus.reg.size());
+
+ while (1)
+ {
+ word t=f[0];
+ while (!t)
+ {
+ ShiftWordsRightByWords(f, fgLen, 1);
+ if (c[bcLen-1])
+ bcLen++;
+ assert(bcLen <= m_modulus.reg.size());
+ ShiftWordsLeftByWords(c, bcLen, 1);
+ k+=WORD_BITS;
+ t=f[0];
+ }
+
+ unsigned int i=0;
+ while (t%2 == 0)
+ {
+ t>>=1;
+ i++;
+ }
+ k+=i;
+
+ if (t==1 && CountWords(f, fgLen)==1)
+ break;
+
+ if (i==1)
+ {
+ ShiftWordsRightByBits(f, fgLen, 1);
+ t=ShiftWordsLeftByBits(c, bcLen, 1);
+ }
+ else
+ {
+ ShiftWordsRightByBits(f, fgLen, i);
+ t=ShiftWordsLeftByBits(c, bcLen, i);
+ }
+ if (t)
+ {
+ c[bcLen] = t;
+ bcLen++;
+ assert(bcLen <= m_modulus.reg.size());
+ }
+
+ if (f[fgLen-1]==0 && g[fgLen-1]==0)
+ fgLen--;
+
+ if (f[fgLen-1] < g[fgLen-1])
+ {
+ std::swap(f, g);
+ std::swap(b, c);
+ }
+
+ XorWords(f, g, fgLen);
+ XorWords(b, c, bcLen);
+ }
+
+ while (k >= WORD_BITS)
+ {
+ word temp = b[0];
+ // right shift b
+ for (unsigned i=0; i+1<BitsToWords(m); i++)
+ b[i] = b[i+1];
+ b[BitsToWords(m)-1] = 0;
+
+ if (t1 < WORD_BITS)
+ for (unsigned int j=0; j<WORD_BITS-t1; j++)
+ temp ^= ((temp >> j) & 1) << (t1 + j);
+ else
+ b[t1/WORD_BITS-1] ^= temp << t1%WORD_BITS;
+
+ if (t1 % WORD_BITS)
+ b[t1/WORD_BITS] ^= temp >> (WORD_BITS - t1%WORD_BITS);
+
+ if (t0%WORD_BITS)
+ {
+ b[t0/WORD_BITS-1] ^= temp << t0%WORD_BITS;
+ b[t0/WORD_BITS] ^= temp >> (WORD_BITS - t0%WORD_BITS);
+ }
+ else
+ b[t0/WORD_BITS-1] ^= temp;
+
+ k -= WORD_BITS;
+ }
+
+ if (k)
+ {
+ word temp = b[0] << (WORD_BITS - k);
+ ShiftWordsRightByBits(b, BitsToWords(m), k);
+
+ if (t1 < WORD_BITS)
+ for (unsigned int j=0; j<WORD_BITS-t1; j++)
+ temp ^= ((temp >> j) & 1) << (t1 + j);
+ else
+ b[t1/WORD_BITS-1] ^= temp << t1%WORD_BITS;
+
+ if (t1 % WORD_BITS)
+ b[t1/WORD_BITS] ^= temp >> (WORD_BITS - t1%WORD_BITS);
+
+ if (t0%WORD_BITS)
+ {
+ b[t0/WORD_BITS-1] ^= temp << t0%WORD_BITS;
+ b[t0/WORD_BITS] ^= temp >> (WORD_BITS - t0%WORD_BITS);
+ }
+ else
+ b[t0/WORD_BITS-1] ^= temp;
+ }
+
+ CopyWords(result.reg.begin(), b, result.reg.size());
+ return result;
+}
+
+const GF2NT::Element& GF2NT::Multiply(const Element &a, const Element &b) const
+{
+ size_t aSize = STDMIN(a.reg.size(), result.reg.size());
+ Element r((word)0, m);
+
+ for (int i=m-1; i>=0; i--)
+ {
+ if (r[m-1])
+ {
+ ShiftWordsLeftByBits(r.reg.begin(), r.reg.size(), 1);
+ XorWords(r.reg.begin(), m_modulus.reg, r.reg.size());
+ }
+ else
+ ShiftWordsLeftByBits(r.reg.begin(), r.reg.size(), 1);
+
+ if (b[i])
+ XorWords(r.reg.begin(), a.reg, aSize);
+ }
+
+ if (m%WORD_BITS)
+ r.reg.begin()[r.reg.size()-1] = (word)Crop(r.reg[r.reg.size()-1], m%WORD_BITS);
+
+ CopyWords(result.reg.begin(), r.reg.begin(), result.reg.size());
+ return result;
+}
+
+const GF2NT::Element& GF2NT::Reduced(const Element &a) const
+{
+ if (t0-t1 < WORD_BITS)
+ return m_domain.Mod(a, m_modulus);
+
+ SecWordBlock b(a.reg);
+
+ size_t i;
+ for (i=b.size()-1; i>=BitsToWords(t0); i--)
+ {
+ word temp = b[i];
+
+ if (t0%WORD_BITS)
+ {
+ b[i-t0/WORD_BITS] ^= temp >> t0%WORD_BITS;
+ b[i-t0/WORD_BITS-1] ^= temp << (WORD_BITS - t0%WORD_BITS);
+ }
+ else
+ b[i-t0/WORD_BITS] ^= temp;
+
+ if ((t0-t1)%WORD_BITS)
+ {
+ b[i-(t0-t1)/WORD_BITS] ^= temp >> (t0-t1)%WORD_BITS;
+ b[i-(t0-t1)/WORD_BITS-1] ^= temp << (WORD_BITS - (t0-t1)%WORD_BITS);
+ }
+ else
+ b[i-(t0-t1)/WORD_BITS] ^= temp;
+ }
+
+ if (i==BitsToWords(t0)-1 && t0%WORD_BITS)
+ {
+ word mask = ((word)1<<(t0%WORD_BITS))-1;
+ word temp = b[i] & ~mask;
+ b[i] &= mask;
+
+ b[i-t0/WORD_BITS] ^= temp >> t0%WORD_BITS;
+
+ if ((t0-t1)%WORD_BITS)
+ {
+ b[i-(t0-t1)/WORD_BITS] ^= temp >> (t0-t1)%WORD_BITS;
+ if ((t0-t1)%WORD_BITS > t0%WORD_BITS)
+ b[i-(t0-t1)/WORD_BITS-1] ^= temp << (WORD_BITS - (t0-t1)%WORD_BITS);
+ else
+ assert(temp << (WORD_BITS - (t0-t1)%WORD_BITS) == 0);
+ }
+ else
+ b[i-(t0-t1)/WORD_BITS] ^= temp;
+ }
+
+ SetWords(result.reg.begin(), 0, result.reg.size());
+ CopyWords(result.reg.begin(), b, STDMIN(b.size(), result.reg.size()));
+ return result;
+}
+
+void GF2NP::DEREncodeElement(BufferedTransformation &out, const Element &a) const
+{
+ a.DEREncodeAsOctetString(out, MaxElementByteLength());
+}
+
+void GF2NP::BERDecodeElement(BufferedTransformation &in, Element &a) const
+{
+ a.BERDecodeAsOctetString(in, MaxElementByteLength());
+}
+
+void GF2NT::DEREncode(BufferedTransformation &bt) const
+{
+ DERSequenceEncoder seq(bt);
+ ASN1::characteristic_two_field().DEREncode(seq);
+ DERSequenceEncoder parameters(seq);
+ DEREncodeUnsigned(parameters, m);
+ ASN1::tpBasis().DEREncode(parameters);
+ DEREncodeUnsigned(parameters, t1);
+ parameters.MessageEnd();
+ seq.MessageEnd();
+}
+
+void GF2NPP::DEREncode(BufferedTransformation &bt) const
+{
+ DERSequenceEncoder seq(bt);
+ ASN1::characteristic_two_field().DEREncode(seq);
+ DERSequenceEncoder parameters(seq);
+ DEREncodeUnsigned(parameters, m);
+ ASN1::ppBasis().DEREncode(parameters);
+ DERSequenceEncoder pentanomial(parameters);
+ DEREncodeUnsigned(pentanomial, t3);
+ DEREncodeUnsigned(pentanomial, t2);
+ DEREncodeUnsigned(pentanomial, t1);
+ pentanomial.MessageEnd();
+ parameters.MessageEnd();
+ seq.MessageEnd();
+}
+
+GF2NP * BERDecodeGF2NP(BufferedTransformation &bt)
+{
+ // VC60 workaround: auto_ptr lacks reset()
+ member_ptr<GF2NP> result;
+
+ BERSequenceDecoder seq(bt);
+ if (OID(seq) != ASN1::characteristic_two_field())
+ BERDecodeError();
+ BERSequenceDecoder parameters(seq);
+ unsigned int m;
+ BERDecodeUnsigned(parameters, m);
+ OID oid(parameters);
+ if (oid == ASN1::tpBasis())
+ {
+ unsigned int t1;
+ BERDecodeUnsigned(parameters, t1);
+ result.reset(new GF2NT(m, t1, 0));
+ }
+ else if (oid == ASN1::ppBasis())
+ {
+ unsigned int t1, t2, t3;
+ BERSequenceDecoder pentanomial(parameters);
+ BERDecodeUnsigned(pentanomial, t3);
+ BERDecodeUnsigned(pentanomial, t2);
+ BERDecodeUnsigned(pentanomial, t1);
+ pentanomial.MessageEnd();
+ result.reset(new GF2NPP(m, t3, t2, t1, 0));
+ }
+ else
+ {
+ BERDecodeError();
+ return NULL;
+ }
+ parameters.MessageEnd();
+ seq.MessageEnd();
+
+ return result.release();
+}
+
+NAMESPACE_END
+
+#endif
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