org.bouncycastle.math.ec.custom.gm

Class SM9P256V1Point

java.lang.Object

org.bouncycastle.math.ec.ECPoint

org.bouncycastle.math.ec.ECPoint.AbstractFp

org.bouncycastle.math.ec.custom.gm.SM9P256V1Point

public class SM9P256V1Point
extends ECPoint.AbstractFp

Jacobian-coordinate point of the SM9 G1 curve y^2 = x^3 + 5 (a = 0) over SM9P256V1Field.

The group law is the standard a=0 Jacobian addition (add-2007-bl) and doubling (dbl-2009-l), written in terms of the ECFieldElement operations so it is correct over the Montgomery-form field. (It does not use the Solinas-specific int[]-level fused reductions that SM2P256V1Point relies on, which are not valid for a Montgomery representation.)

Nested Class Summary

Nested classes/interfaces inherited from class org.bouncycastle.math.ec.ECPoint

ECPoint.AbstractF2m, ECPoint.AbstractFp, ECPoint.F2m, ECPoint.Fp

Field Summary

Fields inherited from class org.bouncycastle.math.ec.ECPoint

curve, EMPTY_ZS, preCompTable, x, y, zs

Method Summary

Modifier and Type	Method and Description
ECPoint	add(ECPoint b)
protected ECPoint	detach()
void	encodeTo(boolean compressed, byte[] buf, int off) Only the uncompressed encoding is written.
int	getEncodedLength(boolean compressed) The compressed length is refused, as encodeTo(boolean, byte[], int) refuses the compressed encoding itself.
ECPoint	negate()
ECPoint	threeTimes()
ECPoint	twice()
ECPoint	twicePlus(ECPoint b)

Methods inherited from class org.bouncycastle.math.ec.ECPoint.AbstractFp

getCompressionYTilde, satisfiesCurveEquation, subtract

Methods inherited from class org.bouncycastle.math.ec.ECPoint

checkNormalized, createScaledPoint, equals, equals, getAffineXCoord, getAffineYCoord, getCurve, getCurveCoordinateSystem, getDetachedPoint, getEncoded, getInitialZCoords, getRawXCoord, getRawYCoord, getRawZCoords, getXCoord, getYCoord, getZCoord, getZCoords, hashCode, isInfinity, isNormalized, isValid, multiply, normalize, satisfiesOrder, scaleX, scaleXNegateY, scaleY, scaleYNegateX, timesPow2, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Method Detail

detach

protected ECPoint detach()

Specified by:

detach in class ECPoint

getEncodedLength

public int getEncodedLength(boolean compressed)

The compressed length is refused, as encodeTo(boolean, byte[], int) refuses the compressed encoding itself.

Overrides:

getEncodedLength in class ECPoint

encodeTo

public void encodeTo(boolean compressed,
                     byte[] buf,
                     int off)

Only the uncompressed encoding is written. The SM9 G1 curve cannot decompress a point - its field has no square root, see SM9P256V1FieldElement.sqrt() - so a compressed encoding written here was one ECCurve.decodePoint(byte[]) on the same curve then refused. The point at infinity keeps its one-octet encoding, which decodes.

Overrides:

encodeTo in class ECPoint

Throws:

java.lang.UnsupportedOperationException - if compressed is true for a finite point.

add

public ECPoint add(ECPoint b)

Specified by:

add in class ECPoint

twice

public ECPoint twice()

Specified by:

twice in class ECPoint

twicePlus

public ECPoint twicePlus(ECPoint b)

Overrides:

twicePlus in class ECPoint

threeTimes

public ECPoint threeTimes()

Overrides:

threeTimes in class ECPoint

negate

public ECPoint negate()

Specified by:

negate in class ECPoint