gfpcrypt.cpp

// dsa.cpp - originally written and placed in the public domain by Wei Dai

#include "pch.h"
#include "config.h"

// TODO: fix the C4589 warnings
#if CRYPTOPP_MSC_VERSION
# pragma warning(disable: 4189 4589)
#endif

#ifndef CRYPTOPP_IMPORTS

#include "gfpcrypt.h"
#include "nbtheory.h"
#include "modarith.h"
#include "integer.h"
#include "asn.h"
#include "oids.h"
#include "misc.h"

NAMESPACE_BEGIN(CryptoPP)

#if defined(CRYPTOPP_DEBUG) && !defined(CRYPTOPP_DOXYGEN_PROCESSING)
void TestInstantiations_gfpcrypt()
{
    GDSA<SHA1>::Signer test;
    GDSA<SHA1>::Verifier test1;
    DSA::Signer test5(NullRNG(), 100);
    DSA::Signer test2(test5);
    NR<SHA1>::Signer test3;
    NR<SHA1>::Verifier test4;
    DLIES<>::Encryptor test6;
    DLIES<>::Decryptor test7;
}
#endif

void DL_GroupParameters_DSA::GenerateRandom(RandomNumberGenerator &rng, const NameValuePairs &alg)
{
    Integer p, q, g;

    if (alg.GetValue("Modulus", p) && alg.GetValue("SubgroupGenerator", g))
    {
        q = alg.GetValueWithDefault("SubgroupOrder", ComputeGroupOrder(p)/2);
        Initialize(p, q, g);
    }
    else
    {
        int modulusSize = 2048, defaultSubgroupOrderSize;
        alg.GetIntValue("ModulusSize", modulusSize) || alg.GetIntValue("KeySize", modulusSize);

        switch (modulusSize)
        {
        case 1024:
            defaultSubgroupOrderSize = 160;
            break;
        case 2048:
            defaultSubgroupOrderSize = 224;
            break;
        case 3072:
            defaultSubgroupOrderSize = 256;
            break;
        default:
            throw InvalidArgument("DSA: not a valid prime length");
        }

        DL_GroupParameters_GFP::GenerateRandom(rng, CombinedNameValuePairs(alg, MakeParameters(Name::SubgroupOrderSize(), defaultSubgroupOrderSize, false)));
    }
}

bool DL_GroupParameters_DSA::ValidateGroup(RandomNumberGenerator &rng, unsigned int level) const
{
    bool pass = DL_GroupParameters_GFP::ValidateGroup(rng, level);
    CRYPTOPP_ASSERT(pass);

    const int pSize = GetModulus().BitCount(), qSize = GetSubgroupOrder().BitCount();
    pass = pass && ((pSize==1024 && qSize==160) || (pSize==2048 && qSize==224) || (pSize==2048 && qSize==256) || (pSize==3072 && qSize==256));
    CRYPTOPP_ASSERT(pass);

    return pass;
}

void DL_SignatureMessageEncodingMethod_DSA::ComputeMessageRepresentative(RandomNumberGenerator &rng,
    const byte *recoverableMessage, size_t recoverableMessageLength,
    HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
    byte *representative, size_t representativeBitLength) const
{
    CRYPTOPP_UNUSED(rng), CRYPTOPP_UNUSED(recoverableMessage), CRYPTOPP_UNUSED(recoverableMessageLength);
    CRYPTOPP_UNUSED(messageEmpty), CRYPTOPP_UNUSED(hashIdentifier);
    CRYPTOPP_ASSERT(recoverableMessageLength == 0);
    CRYPTOPP_ASSERT(hashIdentifier.second == 0);

    const size_t representativeByteLength = BitsToBytes(representativeBitLength);
    const size_t digestSize = hash.DigestSize();
    const size_t paddingLength = SaturatingSubtract(representativeByteLength, digestSize);

    memset(representative, 0, paddingLength);
    hash.TruncatedFinal(representative+paddingLength, STDMIN(representativeByteLength, digestSize));

    if (digestSize*8 > representativeBitLength)
    {
        Integer h(representative, representativeByteLength);
        h >>= representativeByteLength*8 - representativeBitLength;
        h.Encode(representative, representativeByteLength);
    }
}

void DL_SignatureMessageEncodingMethod_NR::ComputeMessageRepresentative(RandomNumberGenerator &rng,
    const byte *recoverableMessage, size_t recoverableMessageLength,
    HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
    byte *representative, size_t representativeBitLength) const
{
    CRYPTOPP_UNUSED(rng);CRYPTOPP_UNUSED(recoverableMessage); CRYPTOPP_UNUSED(recoverableMessageLength);
    CRYPTOPP_UNUSED(hash); CRYPTOPP_UNUSED(hashIdentifier); CRYPTOPP_UNUSED(messageEmpty);
    CRYPTOPP_UNUSED(representative); CRYPTOPP_UNUSED(representativeBitLength);

    CRYPTOPP_ASSERT(recoverableMessageLength == 0);
    CRYPTOPP_ASSERT(hashIdentifier.second == 0);
    const size_t representativeByteLength = BitsToBytes(representativeBitLength);
    const size_t digestSize = hash.DigestSize();
    const size_t paddingLength = SaturatingSubtract(representativeByteLength, digestSize);

    memset(representative, 0, paddingLength);
    hash.TruncatedFinal(representative+paddingLength, STDMIN(representativeByteLength, digestSize));

    if (digestSize*8 >= representativeBitLength)
    {
        Integer h(representative, representativeByteLength);
        h >>= representativeByteLength*8 - representativeBitLength + 1;
        h.Encode(representative, representativeByteLength);
    }
}

bool DL_GroupParameters_IntegerBased::ValidateGroup(RandomNumberGenerator &rng, unsigned int level) const
{
    const Integer &p = GetModulus(), &q = GetSubgroupOrder();

    bool pass = true;
    pass = pass && p > Integer::One() && p.IsOdd();
    CRYPTOPP_ASSERT(pass);
    pass = pass && q > Integer::One() && q.IsOdd();
    CRYPTOPP_ASSERT(pass);

    if (level >= 1)
    {
        pass = pass && GetCofactor() > Integer::One() && GetGroupOrder() % q == Integer::Zero();
        CRYPTOPP_ASSERT(pass);
    }
    if (level >= 2)
    {
        pass = pass && VerifyPrime(rng, q, level-2) && VerifyPrime(rng, p, level-2);
        CRYPTOPP_ASSERT(pass);
    }

    return pass;
}

bool DL_GroupParameters_IntegerBased::ValidateElement(unsigned int level, const Integer &g, const DL_FixedBasePrecomputation<Integer> *gpc) const
{
    const Integer &p = GetModulus(), &q = GetSubgroupOrder();

    bool pass = true;
    pass = pass && GetFieldType() == 1 ? g.IsPositive() : g.NotNegative();
    CRYPTOPP_ASSERT(pass);

    pass = pass && g < p && !IsIdentity(g);
    CRYPTOPP_ASSERT(pass);

    if (level >= 1)
    {
        if (gpc)
        {
            pass = pass && gpc->Exponentiate(GetGroupPrecomputation(), Integer::One()) == g;
            CRYPTOPP_ASSERT(pass);
        }
    }
    if (level >= 2)
    {
        if (GetFieldType() == 2)
        {
            pass = pass && Jacobi(g*g-4, p)==-1;
            CRYPTOPP_ASSERT(pass);
        }

        // verifying that Lucas((p+1)/2, w, p)==2 is omitted because it's too costly
        // and at most 1 bit is leaked if it's false
        bool fullValidate = (GetFieldType() == 2 && level >= 3) || !FastSubgroupCheckAvailable();

        if (fullValidate && pass)
        {
            Integer gp = gpc ? gpc->Exponentiate(GetGroupPrecomputation(), q) : ExponentiateElement(g, q);
            pass = pass && IsIdentity(gp);
            CRYPTOPP_ASSERT(pass);
        }
        else if (GetFieldType() == 1)
        {
            pass = pass && Jacobi(g, p) == 1;
            CRYPTOPP_ASSERT(pass);
        }
    }

    return pass;
}

void DL_GroupParameters_IntegerBased::GenerateRandom(RandomNumberGenerator &rng, const NameValuePairs &alg)
{
    Integer p, q, g;

    if (alg.GetValue("Modulus", p) && alg.GetValue("SubgroupGenerator", g))
    {
        q = alg.GetValueWithDefault("SubgroupOrder", ComputeGroupOrder(p)/2);
    }
    else
    {
        int modulusSize, subgroupOrderSize;

        if (!alg.GetIntValue("ModulusSize", modulusSize))
            modulusSize = alg.GetIntValueWithDefault("KeySize", 2048);

        if (!alg.GetIntValue("SubgroupOrderSize", subgroupOrderSize))
            subgroupOrderSize = GetDefaultSubgroupOrderSize(modulusSize);

        PrimeAndGenerator pg;
        pg.Generate(GetFieldType() == 1 ? 1 : -1, rng, modulusSize, subgroupOrderSize);
        p = pg.Prime();
        q = pg.SubPrime();
        g = pg.Generator();
    }

    Initialize(p, q, g);
}

void DL_GroupParameters_IntegerBased::EncodeElement(bool reversible, const Element &element, byte *encoded) const
{
    CRYPTOPP_UNUSED(reversible);
    element.Encode(encoded, GetModulus().ByteCount());
}

unsigned int DL_GroupParameters_IntegerBased::GetEncodedElementSize(bool reversible) const
{
    CRYPTOPP_UNUSED(reversible);
    return GetModulus().ByteCount();
}

Integer DL_GroupParameters_IntegerBased::DecodeElement(const byte *encoded, bool checkForGroupMembership) const
{
    CRYPTOPP_UNUSED(checkForGroupMembership);
    Integer g(encoded, GetModulus().ByteCount());
    if (!ValidateElement(1, g, NULLPTR))
        throw DL_BadElement();
    return g;
}

void DL_GroupParameters_IntegerBased::BERDecode(BufferedTransformation &bt)
{
    BERSequenceDecoder parameters(bt);
        Integer p(parameters);
        Integer q(parameters);
        Integer g;
        if (parameters.EndReached())
        {
            g = q;
            q = ComputeGroupOrder(p) / 2;
        }
        else
            g.BERDecode(parameters);
    parameters.MessageEnd();

    SetModulusAndSubgroupGenerator(p, g);
    SetSubgroupOrder(q);
}

void DL_GroupParameters_IntegerBased::DEREncode(BufferedTransformation &bt) const
{
    DERSequenceEncoder parameters(bt);
        GetModulus().DEREncode(parameters);
        m_q.DEREncode(parameters);
        GetSubgroupGenerator().DEREncode(parameters);
    parameters.MessageEnd();
}

bool DL_GroupParameters_IntegerBased::GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const
{
    return GetValueHelper<DL_GroupParameters<Element> >(this, name, valueType, pValue)
        CRYPTOPP_GET_FUNCTION_ENTRY(Modulus);
}

void DL_GroupParameters_IntegerBased::AssignFrom(const NameValuePairs &source)
{
    AssignFromHelper(this, source)
        CRYPTOPP_SET_FUNCTION_ENTRY2(Modulus, SubgroupGenerator)
        CRYPTOPP_SET_FUNCTION_ENTRY(SubgroupOrder)
        ;
}

OID DL_GroupParameters_IntegerBased::GetAlgorithmID() const
{
    return ASN1::id_dsa();
}

void DL_GroupParameters_GFP::SimultaneousExponentiate(Element *results, const Element &base, const Integer *exponents, unsigned int exponentsCount) const
{
    ModularArithmetic ma(GetModulus());
    ma.SimultaneousExponentiate(results, base, exponents, exponentsCount);
}

DL_GroupParameters_GFP::Element DL_GroupParameters_GFP::MultiplyElements(const Element &a, const Element &b) const
{
    return a_times_b_mod_c(a, b, GetModulus());
}

DL_GroupParameters_GFP::Element DL_GroupParameters_GFP::CascadeExponentiate(const Element &element1, const Integer &exponent1, const Element &element2, const Integer &exponent2) const
{
    ModularArithmetic ma(GetModulus());
    return ma.CascadeExponentiate(element1, exponent1, element2, exponent2);
}

Integer DL_GroupParameters_IntegerBased::GetMaxExponent() const
{
    return STDMIN(GetSubgroupOrder()-1, Integer::Power2(2*DiscreteLogWorkFactor(GetFieldType()*GetModulus().BitCount())));
}

unsigned int DL_GroupParameters_IntegerBased::GetDefaultSubgroupOrderSize(unsigned int modulusSize) const
{
    return 2*DiscreteLogWorkFactor(GetFieldType()*modulusSize);
}

NAMESPACE_END

#endif