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class MultiSigUtils {
public static void signInput(Transaction tx, int inputIndex, byte[] inputScript, ECKey key) throws AddressFormatException {
TransactionInput input = tx.getInput(inputIndex);
Script existingScriptSig = input.getScriptSig();
int numSigs = Script.decodeFromOpN(inputScript[0]);
ScriptBuilder builder = new ScriptBuilder();
Script redeemScript = new Script(inputScript);
List<ScriptChunk> redeemChunks = redeemScript.getChunks();
int myIndex = findKeyInRedeem(key, redeemChunks);
Sha256Hash hash = tx.hashForSignature(inputIndex, redeemScript.getProgram(), Transaction.SigHash.ALL, false);
TransactionSignature signature = new TransactionSignature(key.sign(hash), Transaction.SigHash.ALL, false);
List<ScriptChunk> existingChunks = existingScriptSig.getChunks();
if (existingChunks.size() < 2)
throw new AddressFormatException("incorrect script size");
// OP_0 required for redeeming multisig due to bug in CHECKMULTISIG in bitcoind
builder.op(ScriptOpCodes.OP_0);
// Collect the signatures
List<byte[]> sigs = Lists.newArrayList();
// collect existing signatures, skipping the initial OP_0 and the final redeem script
for (ScriptChunk chunk : existingChunks.subList(1, existingChunks.size() - 1)) {
if (chunk.isOpCode() || chunk.data.length == 0) {
// OP_0, skip
} else {
sigs.add(chunk.data);
}
}
// Identify location to insert the new sig
boolean inserted = false;
for (ListIterator<byte[]> iter = sigs.listIterator() ; iter.hasNext() ;) {
byte[] sig = iter.next();
if (!inserted && myIndex < findSigInRedeem(sig, hash, redeemChunks)) {
iter.add(signature.encodeToBitcoin());
inserted = true;
break;
}
}
if (!inserted)
sigs.add(signature.encodeToBitcoin());
for (int sig = 0 ; sig < numSigs ; sig++) {
if (sigs.size() > sig)
builder.data(sigs.get(sig));
else
builder.op(ScriptOpCodes.OP_0);
}
if (!Arrays.equals(existingChunks.get(existingChunks.size() - 1).data, inputScript))
throw new AddressFormatException("Existing signature script does not end with the input script. See P2SH standard.");
builder.data(inputScript);
input.setScriptSig(builder.build());
}
public static int findKeyInRedeem(ECKey key, List<ScriptChunk> redeemChunks) throws AddressFormatException {
int numKeys = redeemChunks.get(redeemChunks.size() - 2).data[0] - ScriptOpCodes.OP_1 + 1;
for (int i = 0 ; i < numKeys ; i++) {
if (Arrays.equals(redeemChunks.get(1 + i).data, key.getPubKey())) {
return i;
}
}
throw new AddressFormatException("Could not find matching key");
}
public static int findSigInRedeem(byte[] signatureBytes, Sha256Hash hash, List<ScriptChunk> redeemChunks) throws AddressFormatException {
int numKeys = redeemChunks.get(redeemChunks.size() - 2).data[0] - ScriptOpCodes.OP_1 + 1;
TransactionSignature signature = TransactionSignature.decodeFromBitcoin(signatureBytes, true);
for (int i = 0 ; i < numKeys ; i++) {
if (ECKey.fromPublicOnly(redeemChunks.get(i+1).data).verify(hash, signature)) {
return i;
}
}
throw new AddressFormatException("Could not find matching key for signature");
}
static void sortKeys(List<ECKey> keys) {
final Comparator<byte[]> comparator = UnsignedBytes.lexicographicalComparator();
Collections.sort(keys, new Comparator<ECKey>() {
@Override
public int compare(ECKey k1, ECKey k2) {
return comparator.compare(k1.getPubKey(), k2.getPubKey());
}
});
}
// Get an HD Multisig address
public Address getHdmAddress(List<DeterministicKey> masterKeys, List<ChildNum> path) {
List<ECKey> keys = Lists.newArrayList();
for (DeterministicKey key : masterKeys) {
DeterministicHierarchy hier = new DeterministicHierarchy(key);
DeterministicKey subKey = hier.get(path, true, true);
keys.add(subKey);
}
Script redeemScript = ScriptBuilder.createMultiSigOutputScript(2, keys);
return Address.fromP2SHHash(params, Utils.sha256hash160(expectedRedeemScript.getProgram()));
}
}
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