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gfpcrypt.cpp

00001 // dsa.cpp - written and placed in the public domain by Wei Dai
00002 
00003 #include "pch.h"
00004 
00005 #ifndef CRYPTOPP_IMPORTS
00006 
00007 #include "gfpcrypt.h"
00008 #include "asn.h"
00009 #include "oids.h"
00010 #include "nbtheory.h"
00011 
00012 NAMESPACE_BEGIN(CryptoPP)
00013 
00014 void TestInstantiations_gfpcrypt()
00015 {
00016         GDSA<SHA>::Signer test;
00017         GDSA<SHA>::Verifier test1;
00018         DSA::Signer test5(NullRNG(), 100);
00019         DSA::Signer test2(test5);
00020         NR<SHA>::Signer test3;
00021         NR<SHA>::Verifier test4;
00022         DLIES<>::Encryptor test6;
00023         DLIES<>::Decryptor test7;
00024 }
00025 
00026 void DL_GroupParameters_DSA::GenerateRandom(RandomNumberGenerator &rng, const NameValuePairs &alg)
00027 {
00028         Integer p, q, g;
00029 
00030         if (alg.GetValue("Modulus", p) && alg.GetValue("SubgroupGenerator", g))
00031         {
00032                 q = alg.GetValueWithDefault("SubgroupOrder", ComputeGroupOrder(p)/2);
00033         }
00034         else
00035         {
00036                 int modulusSize = 1024;
00037                 alg.GetIntValue("ModulusSize", modulusSize) || alg.GetIntValue("KeySize", modulusSize);
00038 
00039                 if (!DSA::IsValidPrimeLength(modulusSize))
00040                         throw InvalidArgument("DSA: not a valid prime length");
00041 
00042                 SecByteBlock seed(SHA::DIGESTSIZE);
00043                 Integer h;
00044                 int c;
00045 
00046                 do
00047                 {
00048                         rng.GenerateBlock(seed, SHA::DIGESTSIZE);
00049                 } while (!DSA::GeneratePrimes(seed, SHA::DIGESTSIZE*8, c, p, modulusSize, q));
00050 
00051                 do
00052                 {
00053                         h.Randomize(rng, 2, p-2);
00054                         g = a_exp_b_mod_c(h, (p-1)/q, p);
00055                 } while (g <= 1);
00056         }
00057 
00058         Initialize(p, q, g);
00059 }
00060 
00061 bool DL_GroupParameters_DSA::ValidateGroup(RandomNumberGenerator &rng, unsigned int level) const
00062 {
00063         bool pass = DL_GroupParameters_GFP::ValidateGroup(rng, level);
00064         pass = pass && DSA::IsValidPrimeLength(GetModulus().BitCount());
00065         pass = pass && GetSubgroupOrder().BitCount() == 160;
00066         return pass;
00067 }
00068 
00069 void DL_SignatureMessageEncodingMethod_DSA::ComputeMessageRepresentative(RandomNumberGenerator &rng, 
00070         const byte *recoverableMessage, unsigned int recoverableMessageLength,
00071         HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
00072         byte *representative, unsigned int representativeBitLength) const
00073 {
00074         assert(recoverableMessageLength == 0);
00075         assert(hashIdentifier.second == 0);
00076         const unsigned int representativeByteLength = BitsToBytes(representativeBitLength);
00077         const unsigned int digestSize = hash.DigestSize();
00078         const unsigned int paddingLength = SaturatingSubtract(representativeByteLength, digestSize);
00079 
00080         memset(representative, 0, paddingLength);
00081         hash.TruncatedFinal(representative+paddingLength, STDMIN(representativeByteLength, digestSize));
00082 
00083         if (digestSize*8 > representativeBitLength)
00084         {
00085                 Integer h(representative, representativeByteLength);
00086                 h >>= representativeByteLength*8 - representativeBitLength;
00087                 h.Encode(representative, representativeByteLength);
00088         }
00089 }
00090 
00091 void DL_SignatureMessageEncodingMethod_NR::ComputeMessageRepresentative(RandomNumberGenerator &rng, 
00092         const byte *recoverableMessage, unsigned int recoverableMessageLength,
00093         HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
00094         byte *representative, unsigned int representativeBitLength) const
00095 {
00096         assert(recoverableMessageLength == 0);
00097         assert(hashIdentifier.second == 0);
00098         const unsigned int representativeByteLength = BitsToBytes(representativeBitLength);
00099         const unsigned int digestSize = hash.DigestSize();
00100         const unsigned int paddingLength = SaturatingSubtract(representativeByteLength, digestSize);
00101 
00102         memset(representative, 0, paddingLength);
00103         hash.TruncatedFinal(representative+paddingLength, STDMIN(representativeByteLength, digestSize));
00104 
00105         if (digestSize*8 >= representativeBitLength)
00106         {
00107                 Integer h(representative, representativeByteLength);
00108                 h >>= representativeByteLength*8 - representativeBitLength + 1;
00109                 h.Encode(representative, representativeByteLength);
00110         }
00111 }
00112 
00113 bool DL_GroupParameters_IntegerBased::ValidateGroup(RandomNumberGenerator &rng, unsigned int level) const
00114 {
00115         const Integer &p = GetModulus(), &q = GetSubgroupOrder();
00116 
00117         bool pass = true;
00118         pass = pass && p > Integer::One() && p.IsOdd();
00119         pass = pass && q > Integer::One() && q.IsOdd();
00120 
00121         if (level >= 1)
00122                 pass = pass && GetCofactor() > Integer::One() && GetGroupOrder() % q == Integer::Zero();
00123         if (level >= 2)
00124                 pass = pass && VerifyPrime(rng, q, level-2) && VerifyPrime(rng, p, level-2);
00125 
00126         return pass;
00127 }
00128 
00129 bool DL_GroupParameters_IntegerBased::ValidateElement(unsigned int level, const Integer &g, const DL_FixedBasePrecomputation<Integer> *gpc) const
00130 {
00131         const Integer &p = GetModulus(), &q = GetSubgroupOrder();
00132 
00133         bool pass = true;
00134         pass = pass && GetFieldType() == 1 ? g.IsPositive() : g.NotNegative();
00135         pass = pass && g < p && !IsIdentity(g);
00136 
00137         if (level >= 1)
00138         {
00139                 if (gpc)
00140                         pass = pass && gpc->Exponentiate(GetGroupPrecomputation(), Integer::One()) == g;
00141         }
00142         if (level >= 2)
00143         {
00144                 if (GetFieldType() == 2)
00145                         pass = pass && Jacobi(g*g-4, p)==-1;
00146 
00147                 // verifying that Lucas((p+1)/2, w, p)==2 is omitted because it's too costly
00148                 // and at most 1 bit is leaked if it's false
00149                 bool fullValidate = (GetFieldType() == 2 && level >= 3) || !FastSubgroupCheckAvailable();
00150 
00151                 if (fullValidate)
00152                         pass = pass && IsIdentity(gpc ? gpc->Exponentiate(GetGroupPrecomputation(), q) : ExponentiateElement(g, q));
00153                 else if (GetFieldType() == 1)
00154                         pass = pass && Jacobi(g, p) == 1;
00155         }
00156 
00157         return pass;
00158 }
00159 
00160 void DL_GroupParameters_IntegerBased::GenerateRandom(RandomNumberGenerator &rng, const NameValuePairs &alg)
00161 {
00162         Integer p, q, g;
00163         
00164         if (alg.GetValue("Modulus", p) && alg.GetValue("SubgroupGenerator", g))
00165         {
00166                 q = alg.GetValueWithDefault("SubgroupOrder", ComputeGroupOrder(p)/2);
00167         }
00168         else
00169         {
00170                 int modulusSize, subgroupOrderSize;
00171 
00172                 if (!alg.GetIntValue("ModulusSize", modulusSize))
00173                         modulusSize = alg.GetIntValueWithDefault("KeySize", 2048);
00174 
00175                 if (!alg.GetIntValue("SubgroupOrderSize", subgroupOrderSize))
00176                         subgroupOrderSize = GetDefaultSubgroupOrderSize(modulusSize);
00177 
00178                 PrimeAndGenerator pg;
00179                 pg.Generate(GetFieldType() == 1 ? 1 : -1, rng, modulusSize, subgroupOrderSize);
00180                 p = pg.Prime();
00181                 q = pg.SubPrime();
00182                 g = pg.Generator();
00183         }
00184 
00185         Initialize(p, q, g);
00186 }
00187 
00188 Integer DL_GroupParameters_IntegerBased::DecodeElement(const byte *encoded, bool checkForGroupMembership) const
00189 {
00190         Integer g(encoded, GetModulus().ByteCount());
00191         if (!ValidateElement(1, g, NULL))
00192                 throw DL_BadElement();
00193         return g;
00194 }
00195 
00196 void DL_GroupParameters_IntegerBased::BERDecode(BufferedTransformation &bt)
00197 {
00198         BERSequenceDecoder parameters(bt);
00199                 Integer p(parameters);
00200                 Integer q(parameters);
00201                 Integer g;
00202                 if (parameters.EndReached())
00203                 {
00204                         g = q;
00205                         q = ComputeGroupOrder(p) / 2;
00206                 }
00207                 else
00208                         g.BERDecode(parameters);
00209         parameters.MessageEnd();
00210 
00211         SetModulusAndSubgroupGenerator(p, g);
00212         SetSubgroupOrder(q);
00213 }
00214 
00215 void DL_GroupParameters_IntegerBased::DEREncode(BufferedTransformation &bt) const
00216 {
00217         DERSequenceEncoder parameters(bt);
00218                 GetModulus().DEREncode(parameters);
00219                 m_q.DEREncode(parameters);
00220                 GetSubgroupGenerator().DEREncode(parameters);
00221         parameters.MessageEnd();
00222 }
00223 
00224 bool DL_GroupParameters_IntegerBased::GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const
00225 {
00226         return GetValueHelper<DL_GroupParameters<Element> >(this, name, valueType, pValue)
00227                 CRYPTOPP_GET_FUNCTION_ENTRY(Modulus);
00228 }
00229 
00230 void DL_GroupParameters_IntegerBased::AssignFrom(const NameValuePairs &source)
00231 {
00232         AssignFromHelper(this, source)
00233                 CRYPTOPP_SET_FUNCTION_ENTRY2(Modulus, SubgroupGenerator)
00234                 CRYPTOPP_SET_FUNCTION_ENTRY(SubgroupOrder)
00235                 ;
00236 }
00237 
00238 OID DL_GroupParameters_IntegerBased::GetAlgorithmID() const
00239 {
00240         return ASN1::id_dsa();
00241 }
00242 
00243 void DL_GroupParameters_GFP::SimultaneousExponentiate(Element *results, const Element &base, const Integer *exponents, unsigned int exponentsCount) const
00244 {
00245         ModularArithmetic ma(GetModulus());
00246         ma.SimultaneousExponentiate(results, base, exponents, exponentsCount);
00247 }
00248 
00249 DL_GroupParameters_GFP::Element DL_GroupParameters_GFP::MultiplyElements(const Element &a, const Element &b) const
00250 {
00251         return a_times_b_mod_c(a, b, GetModulus());
00252 }
00253 
00254 DL_GroupParameters_GFP::Element DL_GroupParameters_GFP::CascadeExponentiate(const Element &element1, const Integer &exponent1, const Element &element2, const Integer &exponent2) const
00255 {
00256         ModularArithmetic ma(GetModulus());
00257         return ma.CascadeExponentiate(element1, exponent1, element2, exponent2);
00258 }
00259 
00260 Integer DL_GroupParameters_IntegerBased::GetMaxExponent() const
00261 {
00262         return STDMIN(GetSubgroupOrder()-1, Integer::Power2(2*DiscreteLogWorkFactor(GetFieldType()*GetModulus().BitCount())));
00263 }
00264 
00265 unsigned int DL_GroupParameters_IntegerBased::GetDefaultSubgroupOrderSize(unsigned int modulusSize) const
00266 {
00267         return 2*DiscreteLogWorkFactor(GetFieldType()*modulusSize);
00268 }
00269 
00270 NAMESPACE_END
00271 
00272 #endif

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