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bulletproofs: shave off a lot of scalar muls from the g/h construction

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moneromooo-monero 2018-08-07 09:59:14 +00:00
parent 4564a5d17b
commit a49a17618f
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GPG Key ID: 686F07454D6CEFC3
1 changed files with 39 additions and 20 deletions
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59
src/ringct/bulletproofs.cc
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@ -1138,41 +1138,60 @@ bool bulletproof_VERIFY(const std::vector<const Bulletproof*> &proofs)
winv[i] = invert(w[i]);
PERF_TIMER_STOP(VERIFY_line_24_25_invert);
// precalc
PERF_TIMER_START_BP(VERIFY_line_24_25_precalc);
rct::keyV w_cache(1<<rounds);
w_cache[0] = winv[0];
w_cache[1] = w[0];
for (size_t j = 1; j < rounds; ++j)
{
const size_t slots = 1<<(j+1);
for (size_t s = slots; s-- > 0; --s)
{
sc_mul(w_cache[s].bytes, w_cache[s/2].bytes, w[j].bytes);
sc_mul(w_cache[s-1].bytes, w_cache[s/2].bytes, winv[j].bytes);
}
}
PERF_TIMER_STOP(VERIFY_line_24_25_precalc);
for (size_t i = 0; i < MN; ++i)
{
// Convert the index to binary IN REVERSE and construct the scalar exponent
rct::key g_scalar = proof.a;
rct::key h_scalar;
sc_mul(h_scalar.bytes, proof.b.bytes, yinvpow.bytes);
if (i == 0)
h_scalar = proof.b;
else
sc_mul(h_scalar.bytes, proof.b.bytes, yinvpow.bytes);
for (size_t j = rounds; j-- > 0; )
{
size_t J = w.size() - j - 1;
if ((i & (((size_t)1)<<j)) == 0)
{
sc_mul(g_scalar.bytes, g_scalar.bytes, winv[J].bytes);
sc_mul(h_scalar.bytes, h_scalar.bytes, w[J].bytes);
}
else
{
sc_mul(g_scalar.bytes, g_scalar.bytes, w[J].bytes);
sc_mul(h_scalar.bytes, h_scalar.bytes, winv[J].bytes);
}
}
// Convert the index to binary IN REVERSE and construct the scalar exponent
sc_mul(g_scalar.bytes, g_scalar.bytes, w_cache[i].bytes);
sc_mul(h_scalar.bytes, h_scalar.bytes, w_cache[(~i) & (MN-1)].bytes);
// Adjust the scalars using the exponents from PAPER LINE 62
sc_add(g_scalar.bytes, g_scalar.bytes, z.bytes);
CHECK_AND_ASSERT_MES(2+i/N < zpow.size(), false, "invalid zpow index");
CHECK_AND_ASSERT_MES(i%N < twoN.size(), false, "invalid twoN index");
sc_mul(tmp.bytes, zpow[2+i/N].bytes, twoN[i%N].bytes);
sc_muladd(tmp.bytes, z.bytes, ypow.bytes, tmp.bytes);
sc_mulsub(h_scalar.bytes, tmp.bytes, yinvpow.bytes, h_scalar.bytes);
if (i == 0)
{
sc_add(tmp.bytes, tmp.bytes, z.bytes);
sc_sub(h_scalar.bytes, h_scalar.bytes, tmp.bytes);
}
else
{
sc_muladd(tmp.bytes, z.bytes, ypow.bytes, tmp.bytes);
sc_mulsub(h_scalar.bytes, tmp.bytes, yinvpow.bytes, h_scalar.bytes);
}
sc_muladd(z4[i].bytes, g_scalar.bytes, weight.bytes, z4[i].bytes);
sc_muladd(z5[i].bytes, h_scalar.bytes, weight.bytes, z5[i].bytes);
if (i != MN-1)
if (i == 0)
{
yinvpow = yinv;
ypow = y;
}
else if (i != MN-1)
{
sc_mul(yinvpow.bytes, yinvpow.bytes, yinv.bytes);
sc_mul(ypow.bytes, ypow.bytes, y.bytes);