devrandom

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();