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Use BN reduction context in modexp precompile #463

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Mar 11, 2019
Merged

Use BN reduction context in modexp precompile #463

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12 changes: 6 additions & 6 deletions lib/precompiled/05-modexp.js
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Original file line number Diff line number Diff line change
Expand Up @@ -56,14 +56,14 @@ function getAdjustedExponentLength (data) {
return adjustedExpLen
}

// Taken from https://stackoverflow.com/a/1503019
function expmod (B, E, M) {
if (E.isZero()) return new BN(1).mod(M)
var BM = B.mod(M)
var R = expmod(BM, E.divn(2), M)
R = (R.mul(R)).mod(M)
if (E.mod(new BN(2)).isZero()) return R
return (R.mul(BM)).mod(M)
// Red asserts M > 1
if (M.lten(1)) return new BN(0)
const red = BN.red(M)
const redB = B.toRed(red)
const res = redB.redPow(E)
return res.fromRed()
}

function getOOGResults (opts, results) {
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