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/*
 * Copyright www.jingtum.com Inc. 
 * 
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package com.jingtum.core.crypto.ecdsa;

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

import org.bouncycastle.asn1.DERInteger;
import org.bouncycastle.asn1.DERSequenceGenerator;

public class ECDSASignature {
    /** The two components of the signature. */
    public BigInteger r, s;

    /** Constructs a signature with the given components.
     *@param r
     *@param s
     **/
    public ECDSASignature(BigInteger r, BigInteger s) {
        this.r = r;
        this.s = s;
    }

    /**
     * DER is an international standard for serializing data structures which is widely used in cryptography.
     * It's somewhat like protocol buffers but less convenient. This method returns a standard DER encoding
     * of the signature, as recognized by OpenSSL and other libraries.
     * @return A byte buffer as a standard DER encoding
     * of the signature
     */
    public byte[] encodeToDER() {
        try {
            return derByteStream().toByteArray();
        } catch (IOException e) {
            throw new RuntimeException(e);  // Cannot happen.
        }
    }

    protected ByteArrayOutputStream derByteStream() throws IOException {
        // Usually 70-72 bytes.
        ByteArrayOutputStream bos = new ByteArrayOutputStream(72);
        DERSequenceGenerator seq = new DERSequenceGenerator(bos);
        seq.addObject(new DERInteger(r));
        seq.addObject(new DERInteger(s));
        seq.close();
        return bos;
    }
}