esign.cpp

// esign.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: 4589)
#endif

#include "esign.h"
#include "modarith.h"
#include "integer.h"
#include "nbtheory.h"
#include "algparam.h"
#include "sha.h"
#include "asn.h"

NAMESPACE_BEGIN(CryptoPP)

#if defined(CRYPTOPP_DEBUG) && !defined(CRYPTOPP_DOXYGEN_PROCESSING)
void ESIGN_TestInstantiations()
{
    ESIGN<SHA1>::Verifier x1(1, 1);
    ESIGN<SHA1>::Signer x2(NullRNG(), 1);
    ESIGN<SHA1>::Verifier x3(x2);
    ESIGN<SHA1>::Verifier x4(x2.GetKey());
    ESIGN<SHA1>::Verifier x5(x3);
    ESIGN<SHA1>::Signer x6 = x2;

    x6 = x2;
    x3 = ESIGN<SHA1>::Verifier(x2);
    x4 = x2.GetKey();
}
#endif

void ESIGNFunction::BERDecode(BufferedTransformation &bt)
{
    BERSequenceDecoder seq(bt);
        m_n.BERDecode(seq);
        m_e.BERDecode(seq);
    seq.MessageEnd();
}

void ESIGNFunction::DEREncode(BufferedTransformation &bt) const
{
    DERSequenceEncoder seq(bt);
        m_n.DEREncode(seq);
        m_e.DEREncode(seq);
    seq.MessageEnd();
}

Integer ESIGNFunction::ApplyFunction(const Integer &x) const
{
    DoQuickSanityCheck();
    return STDMIN(a_exp_b_mod_c(x, m_e, m_n) >> (2*GetK()+2), MaxImage());
}

bool ESIGNFunction::Validate(RandomNumberGenerator& rng, unsigned int level) const
{
    CRYPTOPP_UNUSED(rng), CRYPTOPP_UNUSED(level);
    bool pass = true;
    pass = pass && m_n > Integer::One() && m_n.IsOdd();
    CRYPTOPP_ASSERT(pass);
    pass = pass && m_e >= 8 && m_e < m_n;
    CRYPTOPP_ASSERT(pass);
    return pass;
}

bool ESIGNFunction::GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const
{
    return GetValueHelper(this, name, valueType, pValue).Assignable()
        CRYPTOPP_GET_FUNCTION_ENTRY(Modulus)
        CRYPTOPP_GET_FUNCTION_ENTRY(PublicExponent)
        ;
}

void ESIGNFunction::AssignFrom(const NameValuePairs &source)
{
    AssignFromHelper(this, source)
        CRYPTOPP_SET_FUNCTION_ENTRY(Modulus)
        CRYPTOPP_SET_FUNCTION_ENTRY(PublicExponent)
        ;
}

// *****************************************************************************

void InvertibleESIGNFunction::GenerateRandom(RandomNumberGenerator &rng, const NameValuePairs &param)
{
    int modulusSize = 1023*2;
    param.GetIntValue("ModulusSize", modulusSize) || param.GetIntValue("KeySize", modulusSize);

    if (modulusSize < 24)
        throw InvalidArgument("InvertibleESIGNFunction: specified modulus size is too small");

    if (modulusSize % 3 != 0)
        throw InvalidArgument("InvertibleESIGNFunction: modulus size must be divisible by 3");

    m_e = param.GetValueWithDefault("PublicExponent", Integer(32));

    if (m_e < 8)
        throw InvalidArgument("InvertibleESIGNFunction: public exponents less than 8 may not be secure");

    // VC70 workaround: putting these after primeParam causes overlapped stack allocation
    ConstByteArrayParameter seedParam;
    SecByteBlock seed;

    const Integer minP = Integer(204) << (modulusSize/3-8);
    const Integer maxP = Integer::Power2(modulusSize/3)-1;
    AlgorithmParameters primeParam = MakeParameters("Min", minP)("Max", maxP)("RandomNumberType", Integer::PRIME);

    if (param.GetValue("Seed", seedParam))
    {
        seed.resize(seedParam.size() + 4);
        std::memcpy(seed + 4, seedParam.begin(), seedParam.size());

        PutWord(false, BIG_ENDIAN_ORDER, seed, (word32)0);
        m_p.GenerateRandom(rng, CombinedNameValuePairs(primeParam, MakeParameters("Seed", ConstByteArrayParameter(seed))));
        PutWord(false, BIG_ENDIAN_ORDER, seed, (word32)1);
        m_q.GenerateRandom(rng, CombinedNameValuePairs(primeParam, MakeParameters("Seed", ConstByteArrayParameter(seed))));
    }
    else
    {
        m_p.GenerateRandom(rng, primeParam);
        m_q.GenerateRandom(rng, primeParam);
    }

    m_n = m_p * m_p * m_q;

    CRYPTOPP_ASSERT(m_n.BitCount() == (unsigned int)modulusSize);
}

void InvertibleESIGNFunction::BERDecode(BufferedTransformation &bt)
{
    BERSequenceDecoder privateKey(bt);
        m_n.BERDecode(privateKey);
        m_e.BERDecode(privateKey);
        m_p.BERDecode(privateKey);
        m_q.BERDecode(privateKey);
    privateKey.MessageEnd();
}

void InvertibleESIGNFunction::DEREncode(BufferedTransformation &bt) const
{
    DERSequenceEncoder privateKey(bt);
        m_n.DEREncode(privateKey);
        m_e.DEREncode(privateKey);
        m_p.DEREncode(privateKey);
        m_q.DEREncode(privateKey);
    privateKey.MessageEnd();
}

Integer InvertibleESIGNFunction::CalculateRandomizedInverse(RandomNumberGenerator &rng, const Integer &x) const
{
    DoQuickSanityCheck();

    Integer pq = m_p * m_q;
    Integer p2 = m_p * m_p;
    Integer r, z, re, a, w0, w1;

    do
    {
        r.Randomize(rng, Integer::Zero(), pq);
        z = x << (2*GetK()+2);
        re = a_exp_b_mod_c(r, m_e, m_n);
        a = (z - re) % m_n;
        Integer::Divide(w1, w0, a, pq);
        if (w1.NotZero())
        {
            ++w0;
            w1 = pq - w1;
        }
    }
    while ((w1 >> (2*GetK()+1)).IsPositive());

    ModularArithmetic modp(m_p);
    Integer t = modp.Divide(w0 * r % m_p, m_e * re % m_p);
    Integer s = r + t*pq;
    CRYPTOPP_ASSERT(s < m_n);

    return s;
}

bool InvertibleESIGNFunction::Validate(RandomNumberGenerator &rng, unsigned int level) const
{
    bool pass = ESIGNFunction::Validate(rng, level);
    CRYPTOPP_ASSERT(pass);
    pass = pass && m_p > Integer::One() && m_p.IsOdd() && m_p < m_n;
    CRYPTOPP_ASSERT(pass);
    pass = pass && m_q > Integer::One() && m_q.IsOdd() && m_q < m_n;
    CRYPTOPP_ASSERT(pass);
    pass = pass && m_p.BitCount() == m_q.BitCount();
    CRYPTOPP_ASSERT(pass);
    if (level >= 1)
    {
        pass = pass && m_p * m_p * m_q == m_n;
        CRYPTOPP_ASSERT(pass);
    }
    if (level >= 2)
    {
        pass = pass && VerifyPrime(rng, m_p, level-2) && VerifyPrime(rng, m_q, level-2);
        CRYPTOPP_ASSERT(pass);
    }
    return pass;
}

bool InvertibleESIGNFunction::GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const
{
    return GetValueHelper<ESIGNFunction>(this, name, valueType, pValue).Assignable()
        CRYPTOPP_GET_FUNCTION_ENTRY(Prime1)
        CRYPTOPP_GET_FUNCTION_ENTRY(Prime2)
        ;
}

void InvertibleESIGNFunction::AssignFrom(const NameValuePairs &source)
{
    AssignFromHelper<ESIGNFunction>(this, source)
        CRYPTOPP_SET_FUNCTION_ENTRY(Prime1)
        CRYPTOPP_SET_FUNCTION_ENTRY(Prime2)
        ;
}

NAMESPACE_END