/*
*******************************************************************************
* BTChip Bitcoin Hardware Wallet Java API
* (c) 2014 BTChip - 1BTChip7VfTnrPra5jqci7ejnMguuHogTn
*
* Licensed 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.btchip.utils;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.math.BigInteger;
import com.btchip.BTChipException;
public class SignatureUtils {
private static final BigInteger HALF_ORDER = new BigInteger(Dump.hexToBin("7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0"));
private static final BigInteger ORDER = new BigInteger(1, Dump.hexToBin("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141"));
public static byte[] canonicalize(byte[] signature, boolean includeHashType, int hashType) throws BTChipException {
ByteArrayInputStream in = new ByteArrayInputStream(signature);
if (in.read() != 0x30) {
throw new BTChipException("Invalid sequence");
}
in.read();
if (in.read() != (byte)0x02) {
throw new BTChipException("Invalid r");
}
int rSize = in.read();
byte[] value = new byte[rSize];
in.read(value, 0, rSize);
BigInteger r = new BigInteger(value);
if (in.read() != (byte)0x02) {
throw new BTChipException("Invalid s");
}
int sSize = in.read();
value = new byte[sSize];
in.read(value, 0, sSize);
BigInteger s = new BigInteger(value);
if (s.compareTo(HALF_ORDER) > 0) {
s = ORDER.subtract(s);
byte[] rByte = r.toByteArray();
byte[] sByte = s.toByteArray();
ByteArrayOutputStream result = new ByteArrayOutputStream(100);
result.write(0x30);
result.write(2 + rByte.length + 2 + sByte.length);
result.write(0x02);
result.write(rByte.length);
result.write(rByte, 0, rByte.length);
result.write(0x02);
result.write(sByte.length);
result.write(sByte, 0, sByte.length);
if (includeHashType) {
result.write(hashType);
}
return result.toByteArray();
}
else {
return signature;
}
}
}