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Fix missed conditions for XTR-DH domain parameters generation 

Formerly we used asserts and they would fire on occassion. This commit makes the condition part of the generation process to avoid the assert.
pull/334/head
Jeffrey Walton 2018-09-04 23:32:59 -04:00
parent c01606e305
commit 44cd7eb1ed
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GPG Key ID: B36AB348921B1838
1 changed files with 24 additions and 8 deletions
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32
xtr.cpp
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@ -13,7 +13,12 @@ NAMESPACE_BEGIN(CryptoPP)
const GFP2Element & GFP2Element::Zero()
{
#if defined(CRYPTOPP_CXX11_DYNAMIC_INIT)
static const GFP2Element s_zero;
return s_zero;
#else
return Singleton<GFP2Element>().Ref();
#endif
}
void XTR_FindPrimesAndGenerator(RandomNumberGenerator &rng, Integer &p, Integer &q, GFP2Element &g, unsigned int pbits, unsigned int qbits)
@ -26,16 +31,23 @@ void XTR_FindPrimesAndGenerator(RandomNumberGenerator &rng, Integer &p, Integer
const Integer minP = Integer::Power2(pbits - 1);
const Integer maxP = Integer::Power2(pbits) - 1;
top:
Integer r1, r2;
do
{
bool qFound = q.Randomize(rng, minQ, maxQ, Integer::PRIME, 7, 12);
CRYPTOPP_UNUSED(qFound); CRYPTOPP_ASSERT(qFound);
bool solutionsExist = SolveModularQuadraticEquation(r1, r2, 1, -1, 1, q);
CRYPTOPP_UNUSED(solutionsExist); CRYPTOPP_ASSERT(solutionsExist);
} while (!p.Randomize(rng, minP, maxP, Integer::PRIME, CRT(rng.GenerateBit()?r1:r2, q, 2, 3, EuclideanMultiplicativeInverse(p, 3)), 3*q));
CRYPTOPP_ASSERT(p % 3 == 2);
CRYPTOPP_ASSERT(((p.Squared() - p + 1) % q).IsZero());
(void)q.Randomize(rng, minQ, maxQ, Integer::PRIME, 7, 12);
// Solution always exists because q === 7 mod 12.
(void)SolveModularQuadraticEquation(r1, r2, 1, -1, 1, q);
// I believe k_i, r1 and r2 are being used slightly different than the
// paper's algorithm. I believe it is leading to the failed asserts.
// Just make the assert part of the condition.
if(!p.Randomize(rng, minP, maxP, Integer::PRIME, CRT(rng.GenerateBit() ?
r1 : r2, q, 2, 3, EuclideanMultiplicativeInverse(p, 3)), 3 * q)) { continue; }
} while (((p % 3U) != 2) || (((p.Squared() - p + 1) % q).NotZero()));
// CRYPTOPP_ASSERT((p % 3U) == 2);
// CRYPTOPP_ASSERT(((p.Squared() - p + 1) % q).IsZero());
GFP2_ONB<ModularArithmetic> gfp2(p);
GFP2Element three = gfp2.ConvertIn(3), t;
@ -51,7 +63,11 @@ void XTR_FindPrimesAndGenerator(RandomNumberGenerator &rng, Integer &p, Integer
if (g != three)
break;
}
CRYPTOPP_ASSERT(XTR_Exponentiate(g, q, p) == three);
if (XTR_Exponentiate(g, q, p) != three)
goto top;
// CRYPTOPP_ASSERT(XTR_Exponentiate(g, q, p) == three);
}
GFP2Element XTR_Exponentiate(const GFP2Element &b, const Integer &e, const Integer &p)