USDT离线签名

本篇文章仍然使用bitcoinj开源项目来解决UDST的离线签名。如果引入bitcoinj请看上篇文章：BTC离线签名

1.上代码：

    /**
     * usdt 离线签名
     *
     * @param privateKey：私钥
     * @param toAddress：接收地址
     * @param amount:转账金额
     * @return
     */
    public String omniSign(String fromAddress, String toAddress, String privateKey, Long amount, Long fee, Integer propertyid, List utxos) throws Exception {
        NetworkParameters networkParameters = isMainNet ? MainNetParams.get() : TestNet3Params.get();
        Transaction tran = new Transaction(networkParameters);
         if(utxos==null||utxos.size()==0){
             throw new Exception("utxo为空");
         }
        //这是比特币的限制最小转账金额，所以很多usdt转账会收到一笔0.00000546的btc
        Long miniBtc = 546L;
        tran.addOutput(Coin.valueOf(miniBtc), Address.fromBase58(networkParameters, toAddress));

        //构建usdt的输出脚本 注意这里的金额是要乘10的8次方
        String usdtHex = "6a146f6d6e69" + String.format("%016x", propertyid) + String.format("%016x", amount);
        tran.addOutput(Coin.valueOf(0L), new Script(Utils.HEX.decode(usdtHex)));

        //如果有找零就添加找零
        String changeAddress = fromAddress;
        Long changeAmount = 0L;
        Long utxoAmount = 0L;
        List needUtxo = new ArrayList<>();
        for (UTXO utxo : utxos) {
            if (utxoAmount > (fee + miniBtc)) {
                break;
            } else {
                needUtxo.add(utxo);
                utxoAmount += utxo.getValue().value;
            }
        }
        changeAmount = utxoAmount - (fee + miniBtc);
        //余额判断
        if (changeAmount < 0) {
            throw new Exception("utxo余额不足");
        }
        if (changeAmount > 0) {
            tran.addOutput(Coin.valueOf(changeAmount), Address.fromBase58(networkParameters, changeAddress));
        }

        //先添加未签名的输入，也就是utxo
        for (UTXO utxo : needUtxo) {
            tran.addInput(utxo.getHash(), utxo.getIndex(), utxo.getScript()).setSequenceNumber(TransactionInput.NO_SEQUENCE - 2);
        }

        //下面就是签名
        for (int i = 0; i < needUtxo.size(); i++) {
            ECKey ecKey = DumpedPrivateKey.fromBase58(networkParameters, privateKey).getKey();
            TransactionInput transactionInput = tran.getInput(i);
            Script scriptPubKey = ScriptBuilder.createOutputScript(Address.fromBase58(networkParameters, fromAddress));
            Sha256Hash hash = tran.hashForSignature(i, scriptPubKey, Transaction.SigHash.ALL, false);
            ECKey.ECDSASignature ecSig = ecKey.sign(hash);
            TransactionSignature txSig = new TransactionSignature(ecSig, Transaction.SigHash.ALL, false);
            transactionInput.setScriptSig(ScriptBuilder.createInputScript(txSig, ecKey));
        }

        //这是签名之后的原始交易，直接去广播就行了
        String signedHex = Hex.toHexString(tran.bitcoinSerialize());
        //这是交易的hash
        String txHash = Hex.toHexString(Utils.reverseBytes(Sha256Hash.hash(Sha256Hash.hash(tran.bitcoinSerialize()))));
        logger.info("fee:{},utxoAmount:{},changeAmount:{}", fee, utxoAmount, changeAmount);
        return signedHex;
    }

    /**
     * 获取矿工费用
     * @param utxos
     * @return
     */
    public Long getOmniFee(List utxos) {
        Long miniBtc = 546L;
        Long feeRate = getFeeRate();
        Long utxoAmount = 0L;
        Long fee = 0L;
        Long utxoSize = 0L;
        for (UTXO output : utxos) {
            utxoSize++;
            if (utxoAmount > (fee + miniBtc)) {
                break;
            } else {
                utxoAmount += output.getValue().value;
                fee = (utxoSize * 148 * 34 * 3 + 10) * feeRate;
            }
        }
        return fee;
    }

    /***
     * 获取未消费列表
     * @param address ：地址
     * @return
     */
    public List getUnspent(String address) {
        List utxos = Lists.newArrayList();
        String host = this.isMainNet ? "blockchain.info" : "testnet.blockchain.info";
        String url = "https://" + host + "/zh-cn/unspent?active=" + address;
        try {
            String httpGet = HttpUtil.sendGet(url, null);//TODO;联网
            if (StringUtils.equals("No free outputs to spend", httpGet)) {
                return utxos;
            }
            JSONObject jsonObject = JSON.parseObject(httpGet);
            JSONArray unspentOutputs = jsonObject.getJSONArray("unspent_outputs");
            List

2.测试：

    @Test
    public void tranaction() throws Exception {
        api.setIsMainNet(false);
        String fromAddress = "mm26iTQBLEga8zJxvqURo81xuKE7y4m3hB";
        String toAddress = "mjsmd3HGE7erguBCqCef2jG98TZrFLX6LY";
        String privateKey = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx";
        List utxos = api.getUnspent(fromAddress);
        Long amount = 10000L;
        Integer propertyid = 1;
        Long fee = api.getOmniFee(utxos);
        String sign = api.omniSign(fromAddress, toAddress, privateKey, amount,fee, propertyid,utxos);
        String txid = api.publishTx(sign);//广播交易
        System.out.println(txid);
    }