diff options
Diffstat (limited to 'core/src/main/java/org/spongycastle/math/ec/ZSignedDigitL2RMultiplier.java')
-rw-r--r-- | core/src/main/java/org/spongycastle/math/ec/ZSignedDigitL2RMultiplier.java | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/core/src/main/java/org/spongycastle/math/ec/ZSignedDigitL2RMultiplier.java b/core/src/main/java/org/spongycastle/math/ec/ZSignedDigitL2RMultiplier.java new file mode 100644 index 00000000..543bb581 --- /dev/null +++ b/core/src/main/java/org/spongycastle/math/ec/ZSignedDigitL2RMultiplier.java @@ -0,0 +1,29 @@ +package org.spongycastle.math.ec; + +import java.math.BigInteger; + +public class ZSignedDigitL2RMultiplier extends AbstractECMultiplier +{ + /** + * 'Zeroless' Signed Digit Left-to-Right. + */ + protected ECPoint multiplyPositive(ECPoint p, BigInteger k) + { + ECPoint addP = p.normalize(), subP = addP.negate(); + + ECPoint R0 = addP; + + int n = k.bitLength(); + int s = k.getLowestSetBit(); + + int i = n; + while (--i > s) + { + R0 = R0.twicePlus(k.testBit(i) ? addP : subP); + } + + R0 = R0.timesPow2(s); + + return R0; + } +} |