276 lines
8.2 KiB
C++
276 lines
8.2 KiB
C++
// dsa.cpp - written and placed in the public domain by Wei Dai
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#include "pch.h"
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#ifndef CRYPTOPP_IMPORTS
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#include "gfpcrypt.h"
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#include "asn.h"
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#include "oids.h"
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#include "nbtheory.h"
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NAMESPACE_BEGIN(CryptoPP)
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void TestInstantiations_gfpcrypt()
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{
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GDSA<SHA>::Signer test;
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GDSA<SHA>::Verifier test1;
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DSA::Signer test5(NullRNG(), 100);
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DSA::Signer test2(test5);
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NR<SHA>::Signer test3;
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NR<SHA>::Verifier test4;
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DLIES<>::Encryptor test6;
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DLIES<>::Decryptor test7;
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}
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void DL_GroupParameters_DSA::GenerateRandom(RandomNumberGenerator &rng, const NameValuePairs &alg)
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{
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Integer p, q, g;
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if (alg.GetValue("Modulus", p) && alg.GetValue("SubgroupGenerator", g))
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{
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q = alg.GetValueWithDefault("SubgroupOrder", ComputeGroupOrder(p)/2);
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}
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else
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{
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int modulusSize = 1024;
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alg.GetIntValue("ModulusSize", modulusSize) || alg.GetIntValue("KeySize", modulusSize);
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if (!DSA::IsValidPrimeLength(modulusSize))
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throw InvalidArgument("DSA: not a valid prime length");
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SecByteBlock seed(SHA::DIGESTSIZE);
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Integer h;
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int c;
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do
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{
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rng.GenerateBlock(seed, SHA::DIGESTSIZE);
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} while (!DSA::GeneratePrimes(seed, SHA::DIGESTSIZE*8, c, p, modulusSize, q));
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do
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{
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h.Randomize(rng, 2, p-2);
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g = a_exp_b_mod_c(h, (p-1)/q, p);
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} while (g <= 1);
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}
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Initialize(p, q, g);
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}
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bool DL_GroupParameters_DSA::ValidateGroup(RandomNumberGenerator &rng, unsigned int level) const
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{
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bool pass = DL_GroupParameters_GFP::ValidateGroup(rng, level);
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pass = pass && DSA::IsValidPrimeLength(GetModulus().BitCount());
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pass = pass && GetSubgroupOrder().BitCount() == 160;
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return pass;
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}
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void DL_SignatureMessageEncodingMethod_DSA::ComputeMessageRepresentative(RandomNumberGenerator &rng,
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const byte *recoverableMessage, size_t recoverableMessageLength,
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HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
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byte *representative, size_t representativeBitLength) const
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{
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assert(recoverableMessageLength == 0);
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assert(hashIdentifier.second == 0);
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const size_t representativeByteLength = BitsToBytes(representativeBitLength);
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const size_t digestSize = hash.DigestSize();
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const size_t paddingLength = SaturatingSubtract(representativeByteLength, digestSize);
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memset(representative, 0, paddingLength);
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hash.TruncatedFinal(representative+paddingLength, STDMIN(representativeByteLength, digestSize));
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if (digestSize*8 > representativeBitLength)
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{
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Integer h(representative, representativeByteLength);
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h >>= representativeByteLength*8 - representativeBitLength;
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h.Encode(representative, representativeByteLength);
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}
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}
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void DL_SignatureMessageEncodingMethod_NR::ComputeMessageRepresentative(RandomNumberGenerator &rng,
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const byte *recoverableMessage, size_t recoverableMessageLength,
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HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
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byte *representative, size_t representativeBitLength) const
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{
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assert(recoverableMessageLength == 0);
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assert(hashIdentifier.second == 0);
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const size_t representativeByteLength = BitsToBytes(representativeBitLength);
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const size_t digestSize = hash.DigestSize();
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const size_t paddingLength = SaturatingSubtract(representativeByteLength, digestSize);
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memset(representative, 0, paddingLength);
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hash.TruncatedFinal(representative+paddingLength, STDMIN(representativeByteLength, digestSize));
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if (digestSize*8 >= representativeBitLength)
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{
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Integer h(representative, representativeByteLength);
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h >>= representativeByteLength*8 - representativeBitLength + 1;
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h.Encode(representative, representativeByteLength);
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}
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}
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bool DL_GroupParameters_IntegerBased::ValidateGroup(RandomNumberGenerator &rng, unsigned int level) const
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{
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const Integer &p = GetModulus(), &q = GetSubgroupOrder();
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bool pass = true;
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pass = pass && p > Integer::One() && p.IsOdd();
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pass = pass && q > Integer::One() && q.IsOdd();
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if (level >= 1)
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pass = pass && GetCofactor() > Integer::One() && GetGroupOrder() % q == Integer::Zero();
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if (level >= 2)
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pass = pass && VerifyPrime(rng, q, level-2) && VerifyPrime(rng, p, level-2);
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return pass;
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}
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bool DL_GroupParameters_IntegerBased::ValidateElement(unsigned int level, const Integer &g, const DL_FixedBasePrecomputation<Integer> *gpc) const
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{
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const Integer &p = GetModulus(), &q = GetSubgroupOrder();
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bool pass = true;
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pass = pass && GetFieldType() == 1 ? g.IsPositive() : g.NotNegative();
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pass = pass && g < p && !IsIdentity(g);
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if (level >= 1)
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{
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if (gpc)
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pass = pass && gpc->Exponentiate(GetGroupPrecomputation(), Integer::One()) == g;
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}
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if (level >= 2)
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{
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if (GetFieldType() == 2)
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pass = pass && Jacobi(g*g-4, p)==-1;
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// verifying that Lucas((p+1)/2, w, p)==2 is omitted because it's too costly
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// and at most 1 bit is leaked if it's false
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bool fullValidate = (GetFieldType() == 2 && level >= 3) || !FastSubgroupCheckAvailable();
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if (fullValidate && pass)
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{
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Integer gp = gpc ? gpc->Exponentiate(GetGroupPrecomputation(), q) : ExponentiateElement(g, q);
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pass = pass && IsIdentity(gp);
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}
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else if (GetFieldType() == 1)
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pass = pass && Jacobi(g, p) == 1;
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}
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return pass;
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}
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void DL_GroupParameters_IntegerBased::GenerateRandom(RandomNumberGenerator &rng, const NameValuePairs &alg)
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{
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Integer p, q, g;
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if (alg.GetValue("Modulus", p) && alg.GetValue("SubgroupGenerator", g))
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{
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q = alg.GetValueWithDefault("SubgroupOrder", ComputeGroupOrder(p)/2);
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}
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else
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{
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int modulusSize, subgroupOrderSize;
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if (!alg.GetIntValue("ModulusSize", modulusSize))
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modulusSize = alg.GetIntValueWithDefault("KeySize", 2048);
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if (!alg.GetIntValue("SubgroupOrderSize", subgroupOrderSize))
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subgroupOrderSize = GetDefaultSubgroupOrderSize(modulusSize);
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PrimeAndGenerator pg;
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pg.Generate(GetFieldType() == 1 ? 1 : -1, rng, modulusSize, subgroupOrderSize);
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p = pg.Prime();
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q = pg.SubPrime();
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g = pg.Generator();
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}
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Initialize(p, q, g);
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}
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Integer DL_GroupParameters_IntegerBased::DecodeElement(const byte *encoded, bool checkForGroupMembership) const
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{
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Integer g(encoded, GetModulus().ByteCount());
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if (!ValidateElement(1, g, NULL))
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throw DL_BadElement();
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return g;
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}
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void DL_GroupParameters_IntegerBased::BERDecode(BufferedTransformation &bt)
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{
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BERSequenceDecoder parameters(bt);
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Integer p(parameters);
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Integer q(parameters);
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Integer g;
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if (parameters.EndReached())
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{
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g = q;
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q = ComputeGroupOrder(p) / 2;
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}
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else
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g.BERDecode(parameters);
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parameters.MessageEnd();
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SetModulusAndSubgroupGenerator(p, g);
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SetSubgroupOrder(q);
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}
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void DL_GroupParameters_IntegerBased::DEREncode(BufferedTransformation &bt) const
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{
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DERSequenceEncoder parameters(bt);
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GetModulus().DEREncode(parameters);
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m_q.DEREncode(parameters);
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GetSubgroupGenerator().DEREncode(parameters);
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parameters.MessageEnd();
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}
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bool DL_GroupParameters_IntegerBased::GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const
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{
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return GetValueHelper<DL_GroupParameters<Element> >(this, name, valueType, pValue)
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CRYPTOPP_GET_FUNCTION_ENTRY(Modulus);
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}
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void DL_GroupParameters_IntegerBased::AssignFrom(const NameValuePairs &source)
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{
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AssignFromHelper(this, source)
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CRYPTOPP_SET_FUNCTION_ENTRY2(Modulus, SubgroupGenerator)
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CRYPTOPP_SET_FUNCTION_ENTRY(SubgroupOrder)
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;
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}
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OID DL_GroupParameters_IntegerBased::GetAlgorithmID() const
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{
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return ASN1::id_dsa();
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}
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void DL_GroupParameters_GFP::SimultaneousExponentiate(Element *results, const Element &base, const Integer *exponents, unsigned int exponentsCount) const
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{
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ModularArithmetic ma(GetModulus());
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ma.SimultaneousExponentiate(results, base, exponents, exponentsCount);
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}
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DL_GroupParameters_GFP::Element DL_GroupParameters_GFP::MultiplyElements(const Element &a, const Element &b) const
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{
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return a_times_b_mod_c(a, b, GetModulus());
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}
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DL_GroupParameters_GFP::Element DL_GroupParameters_GFP::CascadeExponentiate(const Element &element1, const Integer &exponent1, const Element &element2, const Integer &exponent2) const
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{
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ModularArithmetic ma(GetModulus());
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return ma.CascadeExponentiate(element1, exponent1, element2, exponent2);
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}
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Integer DL_GroupParameters_IntegerBased::GetMaxExponent() const
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{
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return STDMIN(GetSubgroupOrder()-1, Integer::Power2(2*DiscreteLogWorkFactor(GetFieldType()*GetModulus().BitCount())));
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}
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unsigned int DL_GroupParameters_IntegerBased::GetDefaultSubgroupOrderSize(unsigned int modulusSize) const
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{
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return 2*DiscreteLogWorkFactor(GetFieldType()*modulusSize);
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}
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NAMESPACE_END
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#endif
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