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The Bouncy Castle Java APIs for the OpenPGP Protocol. The APIs are designed primarily to be used in conjunction with the BC FIPS provider. The APIs may also be used with other providers although if being used in a FIPS context it is the responsibility of the user to ensure that any other providers used are FIPS certified and used appropriately.

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package org.bouncycastle.bcpg;

import java.io.IOException;
import java.math.BigInteger;

import org.bouncycastle.asn1.ASN1ObjectIdentifier;
import org.bouncycastle.asn1.ASN1Primitive;
import org.bouncycastle.math.ec.ECPoint;

/**
 * Base class for an EC Public Key.
 * For subclasses, see {@link ECDHPublicBCPGKey}, {@link ECDSAPublicBCPGKey} or {@link EdDSAPublicBCPGKey}.
 */
public abstract class ECPublicBCPGKey
    extends BCPGObject
    implements BCPGKey
{
    ASN1ObjectIdentifier oid;
    BigInteger 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 = new MPInteger(in).getValue();
    }

    protected ECPublicBCPGKey(
        ASN1ObjectIdentifier oid,
        ECPoint point)
    {
        this.point = new BigInteger(1, point.getEncoded(false));
        this.oid = oid;
    }

    protected ECPublicBCPGKey(
        ASN1ObjectIdentifier oid,
        BigInteger encodedPoint)
    {
        this.point = encodedPoint;
        this.oid = oid;
    }

    /**
     * return "PGP"
     *
     * @see org.bouncycastle.bcpg.BCPGKey#getFormat()
     */
    public String getFormat()
    {
        return "PGP";
    }

    /**
     * return the standard PGP encoding of the key.
     *
     * @see org.bouncycastle.bcpg.BCPGKey#getEncoded()
     */
    public byte[] getEncoded()
    {
        try
        {
            return super.getEncoded();
        }
        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(this.point);
        out.writeObject(point);
    }

    /**
     * @return point
     */
    public BigInteger getEncodedPoint()
    {
        return point;
    }

    /**
     * @return oid
     */
    public ASN1ObjectIdentifier getCurveOID()
    {
        return oid;
    }

    protected static byte[] readBytesOfEncodedLength(
        BCPGInputStream in)
        throws IOException
    {
        int length = in.read();
        if (length < 0)
        {
            throw new IOException("unexpected end-of-stream");
        }
        if (length == 0 || length == 0xFF)
        {
            throw new IOException("future extensions not yet implemented");
        }
        if (length > 127)
        {
            throw new IOException("unsupported OID");
        }

        byte[] buffer = new byte[length + 2];
        in.readFully(buffer, 2, buffer.length - 2);
        buffer[0] = (byte)0x06;
        buffer[1] = (byte)length;

        return buffer;
    }
}