iaik.security.ecc.util
Interface PointCompressor

public interface PointCompressor

All classes supporting the decompression algorithm of ANSI X9.62 must implement this interface. It will be used by the Octet2Point class.

Method Summary

byte[]	compress(FieldElement xCoordinate, FieldElement yCoordinate) Point compression according to ANSI X9.62
AffineCoordinate	decompress(FieldElement xCoordinate, int yBit, EllipticCurve curve) Point decompression for elliptic curves according to ANSI X9.62

Method Detail

compress

public byte[] compress(FieldElement xCoordinate,
                       FieldElement yCoordinate)

Point compression according to ANSI X9.62

Parameters:

xCoordinate - the point's x coordinate

yCoordinate - the point's y coordinate

Returns:

the compressed point

decompress

public AffineCoordinate decompress(FieldElement xCoordinate,
                                   int yBit,
                                   EllipticCurve curve)
                            throws AlgorithmException

Point decompression for elliptic curves according to ANSI X9.62

Parameters:

xCoordinate - the x coordinate of the point

yBit - the rightmost bit of the y coordinate(must be 0 or 1)

curve - the elliptic curve

Returns:

the coordinates in affine representation

Throws:

AlgorithmException - if yBit != 0 or 1 or the square root calculation fails.