Invalid Batch or signature in Savtooth

Question

I am following the tutorial on https://sawtooth.hyperledger.org/docs/core/releases/latest/_autogen/txn_submit_tutorial.html

I have made some changes just to learn about how things actually work, and this is the java code:

import com.google.protobuf.ByteString;

import com.mashape.unirest.http.Unirest;

import sawtooth.sdk.processor.Utils;

import sawtooth.sdk.protobuf.*;

import java.security.KeyPair;

import java.security.KeyPairGenerator;

import java.security.Signature;

import java.security.spec.ECGenParameterSpec;

public class BatchSender {

    public static void main(String[] args) throws Exception{

        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("EC");

        ECGenParameterSpec parameterSpec = new ECGenParameterSpec("secp256k1");

        keyPairGenerator.initialize(parameterSpec);

        KeyPair keyPair = keyPairGenerator.generateKeyPair();

        Signature ecdsaSign = Signature.getInstance("SHA256withECDSA");

        ecdsaSign.initSign(keyPair.getPrivate());

        byte[] publicKeyBytes = keyPair.getPublic().getEncoded();

        String publicKeyHex = Utils.hash512(publicKeyBytes);

        ByteString publicKeyByteString = ByteString.copyFrom(new String(publicKeyBytes),"UTF-8");

        String payload = "{'key':1, 'value':'value comes here'}";

        String payloadBytes = Utils.hash512(payload.getBytes());

        ByteString payloadByteString  = ByteString.copyFrom(payload.getBytes());

        TransactionHeader txnHeader = TransactionHeader.newBuilder().

                setBatcherPubkeyBytes(publicKeyByteString).

                setFamilyName("plain_info").

                setFamilyVersion("1.0").

                addInputs("1cf1266e282c41be5e4254d8820772c5518a2c5a8c0c7f7eda19594a7eb539453e1ed7").

                setNonce("1").

                addOutputs("1cf1266e282c41be5e4254d8820772c5518a2c5a8c0c7f7eda19594a7eb539453e1ed7").

                setPayloadEncoding("application/json").

                setPayloadSha512(payloadBytes).

                setSignerPubkey(publicKeyHex).build();

        ByteString txnHeaderBytes = txnHeader.toByteString();

        ecdsaSign.update(txnHeaderBytes.toByteArray());

        byte[] txnHeaderSignature = ecdsaSign.sign();

        Transaction txn = Transaction.newBuilder().setHeader(txnHeaderBytes).setPayload(payloadByteString).setHeaderSignature(Utils.hash512(txnHeaderSignature)).build();

        BatchHeader batchHeader = BatchHeader.newBuilder().setSignerPubkey(publicKeyHex).addTransactionIds(txn.getHeaderSignature()).build();

        ByteString batchHeaderBytes = batchHeader.toByteString();

        ecdsaSign.update(batchHeaderBytes.toByteArray());

        byte[] batchHeaderSignature = ecdsaSign.sign();

        Batch batch = Batch.newBuilder().setHeader(batchHeaderBytes).setHeaderSignature(Utils.hash512(batchHeaderSignature)).addTransactions(txn).build();

        BatchList batchList = BatchList.newBuilder().addBatches( batch).build();

        ByteString batchBytes = batchList.toByteString();

        String serverResponse =  Unirest.post("http://rest-api:8080/batches").header("Content-Type","application/octet-stream").body(batchBytes.toByteArray()).asString().getBody();

        System.out.println(serverResponse);

    }

}

The docker log is as follows:

sawtooth-validator-default | [2017-11-21 08:20:09.842 DEBUG    interconnect] ServerThread receiving CLIENT_BATCH_SUBMIT_REQUEST message: 1242 bytes

sawtooth-validator-default | [2017-11-21 08:20:09.844 DEBUG    signature_verifier] batch failed signature validation: 30a2f4a24be3e624f5a35b17cb505b65cb8dd41600545c6dcfac7534205091552e171082922d4eb71f1bb186fe49163f349c604b631f64fa8f1cfea1c8bb2818

sawtooth-validator-default | [2017-11-21 08:20:09.844 DEBUG    interconnect] ServerThread sending CLIENT_BATCH_SUBMIT_RESPONSE to b'50b094689ac14b39'

The batch is getting rejected. How to solve this problem?

Answer 1

This will solve your problem

import org.apache.commons.codec.binary.Hex;

Transaction txn = Transaction.newBuilder()

                      .setHeader(txnHeaderBytes)

                      .setPayload(payloadByteString)

                      .setHeaderSignature(Hex.encodeHexString(txnHeaderSignature))

                    .build();

The problem was that you were using sha-512 hash for the signature whereas, you have to use encoded hex string.