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# rw.cpp

    00001 // rw.cpp - written and placed in the public domain by Wei Dai
    00002
    00003 #include "pch.h"
    00004 #include "rw.h"
    00005 #include "nbtheory.h"
    00006 #include "asn.h"
    00007
    00008 #ifndef CRYPTOPP_IMPORTS
    00009
    00010 NAMESPACE_BEGIN(CryptoPP)
    00011
    00012 void RWFunction::BERDecode(BufferedTransformation &bt)
    00013 {
    00014         BERSequenceDecoder seq(bt);
    00015         m_n.BERDecode(seq);
    00016         seq.MessageEnd();
    00017 }
    00018
    00019 void RWFunction::DEREncode(BufferedTransformation &bt) const
    00020 {
    00021         DERSequenceEncoder seq(bt);
    00022         m_n.DEREncode(seq);
    00023         seq.MessageEnd();
    00024 }
    00025
    00026 Integer RWFunction::ApplyFunction(const Integer &in) const
    00027 {
    00028         DoQuickSanityCheck();
    00029
    00030         Integer out = in.Squared()%m_n;
    00031         const word r = 12;
    00032         // this code was written to handle both r = 6 and r = 12,
    00033         // but now only r = 12 is used in P1363
    00034         const word r2 = r/2;
    00035         const word r3a = (16 + 5 - r) % 16;     // n%16 could be 5 or 13
    00036         const word r3b = (16 + 13 - r) % 16;
    00037         const word r4 = (8 + 5 - r/2) % 8;      // n%8 == 5
    00038         switch (out % 16)
    00039         {
    00040         case r:
    00041                 break;
    00042         case r2:
    00043         case r2+8:
    00044                 out <<= 1;
    00045                 break;
    00046         case r3a:
    00047         case r3b:
    00048                 out.Negate();
    00049                 out += m_n;
    00050                 break;
    00051         case r4:
    00052         case r4+8:
    00053                 out.Negate();
    00054                 out += m_n;
    00055                 out <<= 1;
    00056                 break;
    00057         default:
    00058                 out = Integer::Zero();
    00059         }
    00060         return out;
    00061 }
    00062
    00063 bool RWFunction::Validate(RandomNumberGenerator &rng, unsigned int level) const
    00064 {
    00065         bool pass = true;
    00066         pass = pass && m_n > Integer::One() && m_n%8 == 5;
    00067         return pass;
    00068 }
    00069
    00070 bool RWFunction::GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const
    00071 {
    00072         return GetValueHelper(this, name, valueType, pValue).Assignable()
    00073                 CRYPTOPP_GET_FUNCTION_ENTRY(Modulus)
    00074                 ;
    00075 }
    00076
    00077 void RWFunction::AssignFrom(const NameValuePairs &source)
    00078 {
    00079         AssignFromHelper(this, source)
    00080                 CRYPTOPP_SET_FUNCTION_ENTRY(Modulus)
    00081                 ;
    00082 }
    00083
    00084 // *****************************************************************************
    00085 // private key operations:
    00086
    00087 // generate a random private key
    00088 void InvertibleRWFunction::GenerateRandom(RandomNumberGenerator &rng, const NameValuePairs &alg)
    00089 {
    00090         int modulusSize = 2048;
    00091         alg.GetIntValue("ModulusSize", modulusSize) || alg.GetIntValue("KeySize", modulusSize);
    00092
    00093         if (modulusSize < 16)
    00094                 throw InvalidArgument("InvertibleRWFunction: specified modulus length is too small");
    00095
    00096         const NameValuePairs &primeParam = MakeParametersForTwoPrimesOfEqualSize(modulusSize);
    00097         m_p.GenerateRandom(rng, CombinedNameValuePairs(primeParam, MakeParameters("EquivalentTo", 3)("Mod", 8)));
    00098         m_q.GenerateRandom(rng, CombinedNameValuePairs(primeParam, MakeParameters("EquivalentTo", 7)("Mod", 8)));
    00099
    00100         m_n = m_p * m_q;
    00101         m_u = m_q.InverseMod(m_p);
    00102 }
    00103
    00104 void InvertibleRWFunction::BERDecode(BufferedTransformation &bt)
    00105 {
    00106         BERSequenceDecoder seq(bt);
    00107         m_n.BERDecode(seq);
    00108         m_p.BERDecode(seq);
    00109         m_q.BERDecode(seq);
    00110         m_u.BERDecode(seq);
    00111         seq.MessageEnd();
    00112 }
    00113
    00114 void InvertibleRWFunction::DEREncode(BufferedTransformation &bt) const
    00115 {
    00116         DERSequenceEncoder seq(bt);
    00117         m_n.DEREncode(seq);
    00118         m_p.DEREncode(seq);
    00119         m_q.DEREncode(seq);
    00120         m_u.DEREncode(seq);
    00121         seq.MessageEnd();
    00122 }
    00123
    00124 Integer InvertibleRWFunction::CalculateInverse(RandomNumberGenerator &rng, const Integer &in) const
    00125 {
    00126         // no need to do blinding because RW is only used for signatures
    00127
    00128         DoQuickSanityCheck();
    00129
    00130         Integer cp=in%m_p, cq=in%m_q;
    00131
    00132         if (Jacobi(cp, m_p) * Jacobi(cq, m_q) != 1)
    00133         {
    00134                 cp = cp%2 ? (cp+m_p) >> 1 : cp >> 1;
    00135                 cq = cq%2 ? (cq+m_q) >> 1 : cq >> 1;
    00136         }
    00137
    00138         cp = ModularSquareRoot(cp, m_p);
    00139         cq = ModularSquareRoot(cq, m_q);
    00140
    00141         Integer out = CRT(cq, m_q, cp, m_p, m_u);
    00142
    00143         return STDMIN(out, m_n-out);
    00144 }
    00145
    00146 bool InvertibleRWFunction::Validate(RandomNumberGenerator &rng, unsigned int level) const
    00147 {
    00148         bool pass = RWFunction::Validate(rng, level);
    00149         pass = pass && m_p > Integer::One() && m_p%8 == 3 && m_p < m_n;
    00150         pass = pass && m_q > Integer::One() && m_q%8 == 7 && m_q < m_n;
    00151         pass = pass && m_u.IsPositive() && m_u < m_p;
    00152         if (level >= 1)
    00153         {
    00154                 pass = pass && m_p * m_q == m_n;
    00155                 pass = pass && m_u * m_q % m_p == 1;
    00156         }
    00157         if (level >= 2)
    00158                 pass = pass && VerifyPrime(rng, m_p, level-2) && VerifyPrime(rng, m_q, level-2);
    00159         return pass;
    00160 }
    00161
    00162 bool InvertibleRWFunction::GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const
    00163 {
    00164         return GetValueHelper<RWFunction>(this, name, valueType, pValue).Assignable()
    00165                 CRYPTOPP_GET_FUNCTION_ENTRY(Prime1)
    00166                 CRYPTOPP_GET_FUNCTION_ENTRY(Prime2)
    00167                 CRYPTOPP_GET_FUNCTION_ENTRY(MultiplicativeInverseOfPrime2ModPrime1)
    00168                 ;
    00169 }
    00170
    00171 void InvertibleRWFunction::AssignFrom(const NameValuePairs &source)
    00172 {
    00173         AssignFromHelper<RWFunction>(this, source)
    00174                 CRYPTOPP_SET_FUNCTION_ENTRY(Prime1)
    00175                 CRYPTOPP_SET_FUNCTION_ENTRY(Prime2)
    00176                 CRYPTOPP_SET_FUNCTION_ENTRY(MultiplicativeInverseOfPrime2ModPrime1)
    00177                 ;
    00178 }
    00179
    00180 NAMESPACE_END
    00181
    00182 #endif