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// rw.cpp - written and placed in the public domain by Wei Dai
#include "pch.h"
#include "rw.h"
#include "nbtheory.h"
#include "asn.h"
NAMESPACE_BEGIN(CryptoPP)
void EMSA2Pad::ComputeMessageRepresentative(RandomNumberGenerator &rng,
const byte *recoverableMessage, unsigned int recoverableMessageLength,
HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
byte *representative, unsigned int representativeBitLength) const
{
if (representativeBitLength % 8 != 7)
throw PK_SignatureScheme::InvalidKeyLength("EMSA2: EMSA2 requires a key length that is a multiple of 8");
unsigned int digestSize = hash.DigestSize();
if (representativeBitLength < 8*digestSize + 31)
throw PK_SignatureScheme::KeyTooShort();
unsigned int representativeByteLength = BitsToBytes(representativeBitLength);
representative[0] = messageEmpty ? 0x4b : 0x6b;
memset(representative+1, 0xbb, representativeByteLength-digestSize-4); // padd with 0xbb
byte *afterP2 = representative+representativeByteLength-digestSize-3;
afterP2[0] = 0xba;
hash.Final(afterP2+1);
representative[representativeByteLength-2] = *hashIdentifier.first;
representative[representativeByteLength-1] = 0xcc;
}
// *****************************************************************************
void RWFunction::BERDecode(BufferedTransformation &bt)
{
BERSequenceDecoder seq(bt);
m_n.BERDecode(seq);
seq.MessageEnd();
}
void RWFunction::DEREncode(BufferedTransformation &bt) const
{
DERSequenceEncoder seq(bt);
m_n.DEREncode(seq);
seq.MessageEnd();
}
Integer RWFunction::ApplyFunction(const Integer &in) const
{
DoQuickSanityCheck();
Integer out = in.Squared()%m_n;
const word r = 12;
// this code was written to handle both r = 6 and r = 12,
// but now only r = 12 is used in P1363
const word r2 = r/2;
const word r3a = (16 + 5 - r) % 16; // n%16 could be 5 or 13
const word r3b = (16 + 13 - r) % 16;
const word r4 = (8 + 5 - r/2) % 8; // n%8 == 5
switch (out % 16)
{
case r:
break;
case r2:
case r2+8:
out <<= 1;
break;
case r3a:
case r3b:
out.Negate();
out += m_n;
break;
case r4:
case r4+8:
out.Negate();
out += m_n;
out <<= 1;
break;
default:
out = Integer::Zero();
}
return out;
}
bool RWFunction::Validate(RandomNumberGenerator &rng, unsigned int level) const
{
bool pass = true;
pass = pass && m_n > Integer::One() && m_n%8 == 5;
return pass;
}
bool RWFunction::GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const
{
return GetValueHelper(this, name, valueType, pValue).Assignable()
CRYPTOPP_GET_FUNCTION_ENTRY(Modulus)
;
}
void RWFunction::AssignFrom(const NameValuePairs &source)
{
AssignFromHelper(this, source)
CRYPTOPP_SET_FUNCTION_ENTRY(Modulus)
;
}
// *****************************************************************************
// private key operations:
// generate a random private key
void InvertibleRWFunction::GenerateRandom(RandomNumberGenerator &rng, const NameValuePairs &alg)
{
int modulusSize = 2048;
alg.GetIntValue("ModulusSize", modulusSize) || alg.GetIntValue("KeySize", modulusSize);
if (modulusSize < 16)
throw InvalidArgument("InvertibleRWFunction: specified modulus length is too small");
const NameValuePairs &primeParam = MakeParametersForTwoPrimesOfEqualSize(modulusSize);
m_p.GenerateRandom(rng, CombinedNameValuePairs(primeParam, MakeParameters("EquivalentTo", 3)("Mod", 8)));
m_q.GenerateRandom(rng, CombinedNameValuePairs(primeParam, MakeParameters("EquivalentTo", 7)("Mod", 8)));
m_n = m_p * m_q;
m_u = m_q.InverseMod(m_p);
}
void InvertibleRWFunction::BERDecode(BufferedTransformation &bt)
{
BERSequenceDecoder seq(bt);
m_n.BERDecode(seq);
m_p.BERDecode(seq);
m_q.BERDecode(seq);
m_u.BERDecode(seq);
seq.MessageEnd();
}
void InvertibleRWFunction::DEREncode(BufferedTransformation &bt) const
{
DERSequenceEncoder seq(bt);
m_n.DEREncode(seq);
m_p.DEREncode(seq);
m_q.DEREncode(seq);
m_u.DEREncode(seq);
seq.MessageEnd();
}
Integer InvertibleRWFunction::CalculateInverse(RandomNumberGenerator &rng, const Integer &in) const
{
// no need to do blinding because RW is only used for signatures
DoQuickSanityCheck();
Integer cp=in%m_p, cq=in%m_q;
if (Jacobi(cp, m_p) * Jacobi(cq, m_q) != 1)
{
cp = cp%2 ? (cp+m_p) >> 1 : cp >> 1;
cq = cq%2 ? (cq+m_q) >> 1 : cq >> 1;
}
cp = ModularSquareRoot(cp, m_p);
cq = ModularSquareRoot(cq, m_q);
Integer out = CRT(cq, m_q, cp, m_p, m_u);
return STDMIN(out, m_n-out);
}
bool InvertibleRWFunction::Validate(RandomNumberGenerator &rng, unsigned int level) const
{
bool pass = RWFunction::Validate(rng, level);
pass = pass && m_p > Integer::One() && m_p%8 == 3 && m_p < m_n;
pass = pass && m_q > Integer::One() && m_q%8 == 7 && m_q < m_n;
pass = pass && m_u.IsPositive() && m_u < m_p;
if (level >= 1)
{
pass = pass && m_p * m_q == m_n;
pass = pass && m_u * m_q % m_p == 1;
}
if (level >= 2)
pass = pass && VerifyPrime(rng, m_p, level-2) && VerifyPrime(rng, m_q, level-2);
return pass;
}
bool InvertibleRWFunction::GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const
{
return GetValueHelper<RWFunction>(this, name, valueType, pValue).Assignable()
CRYPTOPP_GET_FUNCTION_ENTRY(Prime1)
CRYPTOPP_GET_FUNCTION_ENTRY(Prime2)
CRYPTOPP_GET_FUNCTION_ENTRY(MultiplicativeInverseOfPrime2ModPrime1)
;
}
void InvertibleRWFunction::AssignFrom(const NameValuePairs &source)
{
AssignFromHelper<RWFunction>(this, source)
CRYPTOPP_SET_FUNCTION_ENTRY(Prime1)
CRYPTOPP_SET_FUNCTION_ENTRY(Prime2)
CRYPTOPP_SET_FUNCTION_ENTRY(MultiplicativeInverseOfPrime2ModPrime1)
;
}
NAMESPACE_END
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