/**
* Create a program that satisfies an OP_CHECKMULTISIG program, using pre-encoded signatures.
* Optionally, appends the script program bytes if spending a P2SH output.
*/
public static Script createMultiSigInputScriptBytes(
List<byte[]> signatures, @Nullable byte[] multisigProgramBytes) {
checkArgument(signatures.size() <= 16);
ScriptBuilder builder = new ScriptBuilder();
builder.smallNum(
0); // Work around a bug in CHECKMULTISIG that is now a required part of the protocol.
for (byte[] signature : signatures) builder.data(signature);
if (multisigProgramBytes != null) builder.data(multisigProgramBytes);
return builder.build();
}
/**
* Returns a copy of the given scriptSig with the signature inserted in the given position.
*
* <p>This function assumes that any missing sigs have OP_0 placeholders. If given scriptSig
* already has all the signatures in place, IllegalArgumentException will be thrown.
*
* @param targetIndex where to insert the signature
* @param sigsPrefixCount how many items to copy verbatim (e.g. initial OP_0 for multisig)
* @param sigsSuffixCount how many items to copy verbatim at end (e.g. redeemScript for P2SH)
*/
public static Script updateScriptWithSignature(
Script scriptSig,
byte[] signature,
int targetIndex,
int sigsPrefixCount,
int sigsSuffixCount) {
ScriptBuilder builder = new ScriptBuilder();
List<ScriptChunk> inputChunks = scriptSig.getChunks();
int totalChunks = inputChunks.size();
// Check if we have a place to insert, otherwise just return given scriptSig unchanged.
// We assume here that OP_0 placeholders always go after the sigs, so
// to find if we have sigs missing, we can just check the chunk in latest sig position
boolean hasMissingSigs = inputChunks.get(totalChunks - sigsSuffixCount - 1).equalsOpCode(OP_0);
checkArgument(hasMissingSigs, "ScriptSig is already filled with signatures");
// copy the prefix
for (ScriptChunk chunk : inputChunks.subList(0, sigsPrefixCount)) builder.addChunk(chunk);
// copy the sigs
int pos = 0;
boolean inserted = false;
for (ScriptChunk chunk : inputChunks.subList(sigsPrefixCount, totalChunks - sigsSuffixCount)) {
if (pos == targetIndex) {
inserted = true;
builder.data(signature);
pos++;
}
if (!chunk.equalsOpCode(OP_0)) {
builder.addChunk(chunk);
pos++;
}
}
// add OP_0's if needed, since we skipped them in the previous loop
while (pos < totalChunks - sigsPrefixCount - sigsSuffixCount) {
if (pos == targetIndex) {
inserted = true;
builder.data(signature);
} else {
builder.addChunk(new ScriptChunk(OP_0, null));
}
pos++;
}
// copy the suffix
for (ScriptChunk chunk : inputChunks.subList(totalChunks - sigsSuffixCount, totalChunks))
builder.addChunk(chunk);
checkState(inserted);
return builder.build();
}
/**
* Creates a program that requires at least N of the given keys to sign, using OP_CHECKMULTISIG.
*/
public static Script createMultiSigOutputScript(int threshold, List<ECKey> pubkeys) {
checkArgument(threshold > 0);
checkArgument(threshold <= pubkeys.size());
checkArgument(pubkeys.size() <= 16); // That's the max we can represent with a single opcode.
ScriptBuilder builder = new ScriptBuilder();
builder.smallNum(threshold);
for (ECKey key : pubkeys) {
builder.data(key.getPubKey());
}
builder.smallNum(pubkeys.size());
builder.op(OP_CHECKMULTISIG);
return builder.build();
}