org.spongycastle.bcpg.ECPublicBCPGKey Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of pg Show documentation
Show all versions of pg Show documentation
Spongy Castle is a package-rename (org.bouncycastle.* to org.spongycastle.*) of Bouncy Castle
intended for the Android platform. Android unfortunately ships with a stripped-down version of
Bouncy Castle, which prevents easy upgrades - Spongy Castle overcomes this and provides a full,
up-to-date version of the Bouncy Castle cryptographic libs.
package org.spongycastle.bcpg;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.math.BigInteger;
import org.spongycastle.asn1.ASN1ObjectIdentifier;
import org.spongycastle.asn1.ASN1Primitive;
import org.spongycastle.asn1.x9.ECNamedCurveTable;
import org.spongycastle.asn1.x9.X9ECParameters;
import org.spongycastle.math.ec.ECCurve;
import org.spongycastle.math.ec.ECPoint;
/**
* base class for an EC Public Key.
*/
public abstract class ECPublicBCPGKey
extends BCPGObject
implements BCPGKey
{
ASN1ObjectIdentifier oid;
ECPoint point;
/**
* @param in the stream to read the packet from.
*/
protected ECPublicBCPGKey(
BCPGInputStream in)
throws IOException
{
this.oid = ASN1ObjectIdentifier.getInstance(ASN1Primitive.fromByteArray(readBytesOfEncodedLength(in)));
this.point = decodePoint(new MPInteger(in).getValue(), oid);
}
protected ECPublicBCPGKey(
ASN1ObjectIdentifier oid,
ECPoint point)
{
this.point = point.normalize();
this.oid = oid;
}
protected ECPublicBCPGKey(
BigInteger encodedPoint,
ASN1ObjectIdentifier oid)
throws IOException
{
this.point = decodePoint(encodedPoint, oid);
this.oid = oid;
}
/**
* return "PGP"
*
* @see org.spongycastle.bcpg.BCPGKey#getFormat()
*/
public String getFormat()
{
return "PGP";
}
/**
* return the standard PGP encoding of the key.
*
* @see org.spongycastle.bcpg.BCPGKey#getEncoded()
*/
public byte[] getEncoded()
{
try
{
ByteArrayOutputStream bOut = new ByteArrayOutputStream();
BCPGOutputStream pgpOut = new BCPGOutputStream(bOut);
pgpOut.writeObject(this);
return bOut.toByteArray();
}
catch (IOException e)
{
return null;
}
}
public void encode(
BCPGOutputStream out)
throws IOException
{
byte[] oid = this.oid.getEncoded();
out.write(oid, 1, oid.length - 1);
MPInteger point = new MPInteger(new BigInteger(1, this.point.getEncoded()));
out.writeObject(point);
}
/**
* @return point
*/
public ECPoint getPoint()
{
return point;
}
/**
* @return oid
*/
public ASN1ObjectIdentifier getCurveOID()
{
return oid;
}
protected static byte[] readBytesOfEncodedLength(
BCPGInputStream in)
throws IOException
{
int length = in.read();
if (length == 0 || length == 0xFF)
{
throw new IOException("future extensions not yet implemented.");
}
byte[] buffer = new byte[length + 2];
in.readFully(buffer, 2, buffer.length - 2);
buffer[0] = (byte)0x06;
buffer[1] = (byte)length;
return buffer;
}
private static ECPoint decodePoint(
BigInteger encodedPoint,
ASN1ObjectIdentifier oid)
throws IOException
{
X9ECParameters curve = ECNamedCurveTable.getByOID(oid);
if (curve == null)
{
throw new IOException(oid.getId() + " does not match any known curve.");
}
if (!(curve.getCurve() instanceof ECCurve.Fp))
{
throw new IOException("Only FPCurves are supported.");
}
return curve.getCurve().decodePoint(encodedPoint.toByteArray());
}
}