iaik.security.ecc.util
Class PointCoDecImpl

java.lang.Object
  iaik.security.ecc.util.PointCoDecImpl

All Implemented Interfaces:

PointCoDec

public class PointCoDecImpl

extends java.lang.Object

implements PointCoDec

Implements the PointCodec Interface. Tries to load the Pointcompressor class and if the succeeds the point compression is enabled.

Field Summary

protected PointCompressor	decompressor_ The compressor implementation.
protected int	supportedCompressions_ depends on the supported compression methods.
protected boolean	verifyOnCurve_ if true the getPoint method evaluates if the new point is indeed on the curve.

Fields inherited from interface iaik.security.ecc.util.PointCoDec

COMPRESSED, PC_COMPRESSED, PC_UNCOMPRESSED, UNCOMPRESSED

Constructor Summary

protected

PointCoDecImpl() Default constructor tries to load the decompressor class and if this succeeds the point compression will be available.

Method Summary

protected AffineCoordinate	compressed(byte[] point, EllipticCurve curve) Performs the Octet String to Point conversation for compressed points.
AffineCoordinate	decodePoint(byte[] encodedPoint, EllipticCurve curve) Performs the Octet String to Point conversation as defined in ANSI X9.62.
byte[]	encodePoint(AffineCoordinate coordinate, int compressionAlgorithm) Encodes the coordinates.
int	getSupportedCompressions() Returns all supported compression algorithms.
boolean	getVerifyPoint() The last step of the Octet String to Point conversation can check if the calculated point indeed is on the curve.
void	setVerifyPoint(boolean doCheck) The last step of the Octet String to Point conversation can check if the calculated point indeed is on the curve.
protected AffineCoordinate	uncompressed(byte[] point, EllipticCurve curve) Performs the Octet String to Point conversation for uncompressed points

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

decompressor_

protected PointCompressor decompressor_

The compressor implementation. If null point compression is disabled.

supportedCompressions_

protected int supportedCompressions_

depends on the supported compression methods.

verifyOnCurve_

protected boolean verifyOnCurve_

if true the getPoint method evaluates if the new point is indeed on the curve.

Constructor Detail

PointCoDecImpl

protected PointCoDecImpl()

Default constructor tries to load the decompressor class and if this succeeds the point compression will be available.

Method Detail

decodePoint

public AffineCoordinate decodePoint(byte[] encodedPoint,
                                    EllipticCurve curve)
                             throws ECCException

Performs the Octet String to Point conversation as defined in ANSI X9.62. If the point uses a compressed format, this class tries to load the decompression classes by name, which might not be available in all distributions.

Specified by:

decodePoint in interface PointCoDec

Parameters:

encodedPoint - the encoded point as byte array.

curve - the elliptic curve containing the encoded point.

Returns:

the coordinates of the encoded point.

Throws:

ECCException - if the decoding algorithm is not implemented (e.g. point decompression)

See Also:

PointCompressor

encodePoint

public byte[] encodePoint(AffineCoordinate coordinate,
                          int compressionAlgorithm)
                   throws ECCException

Encodes the coordinates.

Specified by:

encodePoint in interface PointCoDec

Parameters:

coordinate - the X and Y coordinates to be encoded

compressionAlgorithm - the allowed compression algorithm(s). If more than one the uncompressed form will be used.

Returns:

the encoded point as required by the ASN.1 syntax.

Throws:

ECCException - if the point compression algorithm is not supported.

See Also:

PointCoDec.encodePoint(iaik.security.ecc.math.ecgroup.AffineCoordinate, int)

getSupportedCompressions

public int getSupportedCompressions()

Description copied from interface: PointCoDec

Returns all supported compression algorithms.

Specified by:

getSupportedCompressions in interface PointCoDec

Returns:

one of the defined constants or combination of them.

See Also:

PointCoDec.getSupportedCompressions()

getVerifyPoint

public boolean getVerifyPoint()

The last step of the Octet String to Point conversation can check if the calculated point indeed is on the curve.

Returns:

true if the check is enabled.

setVerifyPoint

public void setVerifyPoint(boolean doCheck)

The last step of the Octet String to Point conversation can check if the calculated point indeed is on the curve. With this method you can swith on/off this feature. On default this feature is disabled.

Parameters:

doCheck - if true the check will be performed

compressed

protected AffineCoordinate compressed(byte[] point,
                                      EllipticCurve curve)
                               throws ECCException

Performs the Octet String to Point conversation for compressed points. This may cause patent issues. Depending of the existence of the proper class this method may cause an exception.

Parameters:

point - the octet string to be converted into a point, including the PC byte.

curve - the elliptic curve, where the point should be on.

Throws:

ECCException - if the point data is invalid or the implementation is not available

uncompressed

protected AffineCoordinate uncompressed(byte[] point,
                                        EllipticCurve curve)
                                 throws ECCException

Performs the Octet String to Point conversation for uncompressed points

Parameters:

point - the octet string to be converted into a point, including the PC byte.

curve - the elliptic curve, where the point should be on.

Throws:

ECCException - if the point data is invalid