@@ -51,8 +51,8 @@ return bb.localStateDB.Reset(batchNum, fromSynchronizer)
 }
 
 // BuildBatch takes the transactions and returns the common.ZKInputs of the next batch
-func (bb *BatchBuilder) BuildBatch(configBatch *ConfigBatch, l1usertxs, l1coordinatortxs []*common.L1Tx, l2txs []*common.L2Tx, tokenIDs []common.TokenID) (*common.ZKInputs, error) {
-	zkInputs, _, err := bb.localStateDB.ProcessTxs(false, l1usertxs, l1coordinatortxs, l2txs)
+func (bb *BatchBuilder) BuildBatch(configBatch *ConfigBatch, l1usertxs, l1coordinatortxs []*common.L1Tx, pooll2txs []*common.PoolL2Tx, tokenIDs []common.TokenID) (*common.ZKInputs, error) {
+	zkInputs, _, err := bb.localStateDB.ProcessTxs(false, true, l1usertxs, l1coordinatortxs, pooll2txs)
 	if err != nil {
 		return nil, err
 	}

@@ -30,3 +30,28 @@ Fee:     tx.Fee,
 		Type:    tx.Type,
 	}
 }
+
+// PoolL2Tx returns the data structure of PoolL2Tx with the parameters of a
+// L2Tx filled
+func (tx *L2Tx) PoolL2Tx() *PoolL2Tx {
+	return &PoolL2Tx{
+		TxID:     tx.TxID,
+		BatchNum: tx.BatchNum,
+		FromIdx:  tx.FromIdx,
+		ToIdx:    tx.ToIdx,
+		Amount:   tx.Amount,
+		Fee:      tx.Fee,
+		Nonce:    tx.Nonce,
+		Type:     tx.Type,
+	}
+}
+
+// L2TxsToPoolL2Txs returns an array of []*PoolL2Tx from an array of []*L2Tx,
+// where the PoolL2Tx only have the parameters of a L2Tx filled.
+func L2TxsToPoolL2Txs(txs []*L2Tx) []*PoolL2Tx {
+	var r []*PoolL2Tx
+	for _, tx := range txs {
+		r = append(r, tx.PoolL2Tx())
+	}
+	return r
+}

@@ -221,8 +221,7 @@ // 4. Call BatchBuilder with TxSelector output
 	configBatch := &batchbuilder.ConfigBatch{
 		ForgerAddress: c.config.ForgerAddress,
 	}
-	l2Txs := common.PoolL2TxsToL2Txs(poolL2Txs)
-	zkInputs, err := c.batchBuilder.BuildBatch(configBatch, l1UserTxsExtra, l1OperatorTxs, l2Txs, nil) // TODO []common.TokenID --> feesInfo
+	zkInputs, err := c.batchBuilder.BuildBatch(configBatch, l1UserTxsExtra, l1OperatorTxs, poolL2Txs, nil) // TODO []common.TokenID --> feesInfo
 	if err != nil {
 		return err
 	}

@@ -43,6 +43,8 @@ db           *pebble.PebbleStorage
 	mt           *merkletree.MerkleTree
 	// idx holds the current Idx that the BatchBuilder is using
 	idx common.Idx
+	zki *common.ZKInputs
+	i   int // i is used for zki
 }
 
 // NewStateDB creates a new StateDB, allowing to use an in-memory or in-disk

@@ -1,8 +1,12 @@
 package statedb
 
 import (
+	"bytes"
+	"errors"
+	"fmt"
 	"math/big"
 
+	ethCommon "github.com/ethereum/go-ethereum/common"
 	"github.com/hermeznetwork/hermez-node/common"
 	"github.com/iden3/go-iden3-crypto/poseidon"
 	"github.com/iden3/go-merkletree"
@@ -10,19 +14,42 @@ "github.com/iden3/go-merkletree/db"
 	"github.com/iden3/go-merkletree/db/memory"
 )
 
-// keyidx is used as key in the db to store the current Idx
-var keyidx = []byte("idx")
+var (
+	// keyidx is used as key in the db to store the current Idx
+	keyidx = []byte("idx")
+
+	ffAddr = ethCommon.HexToAddress("0xffffffffffffffffffffffffffffffffffffffff")
+)
+
+func (s *StateDB) resetZKInputs() {
+	s.zki = nil
+	s.i = 0
+}
 
 // ProcessTxs process the given L1Txs & L2Txs applying the needed updates to
 // the StateDB depending on the transaction Type. Returns the common.ZKInputs
 // to generate the SnarkProof later used by the BatchBuilder, and if
 // cmpExitTree is set to true, returns common.ExitTreeLeaf that is later used
 // by the Synchronizer to update the HistoryDB.
-func (s *StateDB) ProcessTxs(cmpExitTree bool, l1usertxs, l1coordinatortxs []*common.L1Tx, l2txs []*common.L2Tx) (*common.ZKInputs, []*common.ExitInfo, error) {
+func (s *StateDB) ProcessTxs(cmpExitTree, cmpZKInputs bool, l1usertxs, l1coordinatortxs []*common.L1Tx, l2txs []*common.PoolL2Tx) (*common.ZKInputs, []*common.ExitInfo, error) {
 	var err error
 	var exitTree *merkletree.MerkleTree
 	exits := make(map[common.Idx]common.Account)
 
+	if s.zki != nil {
+		return nil, nil, errors.New("Expected StateDB.zki==nil, something went wrong ans is not empty")
+	}
+	defer s.resetZKInputs()
+
+	nTx := len(l1usertxs) + len(l1coordinatortxs) + len(l2txs)
+	if nTx == 0 {
+		return nil, nil, nil // TBD if return an error in the case of no Txs to process
+	}
+
+	if cmpZKInputs {
+		s.zki = common.NewZKInputs(nTx, 24, 32) // TODO this values will be parameters of the function
+	}
+
 	// TBD if ExitTree is only in memory or stored in disk, for the moment
 	// only needed in memory
 	exitTree, err = merkletree.NewMerkleTree(memory.NewMemoryStorage(), s.mt.MaxLevels())
@@ -30,7 +57,8 @@ if err != nil {
 		return nil, nil, err
 	}
 
-	for _, tx := range l1coordinatortxs {
+	// assumption: l1usertx are sorted by L1Tx.Position
+	for _, tx := range l1usertxs {
 		exitIdx, exitAccount, err := s.processL1Tx(exitTree, tx)
 		if err != nil {
 			return nil, nil, err
@@ -38,8 +66,11 @@ }
 		if exitIdx != nil && cmpExitTree {
 			exits[*exitIdx] = *exitAccount
 		}
+		if s.zki != nil {
+			s.i++
+		}
 	}
-	for _, tx := range l1usertxs {
+	for _, tx := range l1coordinatortxs {
 		exitIdx, exitAccount, err := s.processL1Tx(exitTree, tx)
 		if err != nil {
 			return nil, nil, err
@@ -47,6 +78,9 @@ }
 		if exitIdx != nil && cmpExitTree {
 			exits[*exitIdx] = *exitAccount
 		}
+		if s.zki != nil {
+			s.i++
+		}
 	}
 	for _, tx := range l2txs {
 		exitIdx, exitAccount, err := s.processL2Tx(exitTree, tx)
@@ -56,9 +90,12 @@ }
 		if exitIdx != nil && cmpExitTree {
 			exits[*exitIdx] = *exitAccount
 		}
+		if s.zki != nil {
+			s.i++
+		}
 	}
 
-	if !cmpExitTree {
+	if !cmpExitTree && !cmpZKInputs {
 		return nil, nil, nil
 	}
 
@@ -93,15 +130,78 @@ Balance:     exitAccount.Balance,
 		}
 		exitInfos = append(exitInfos, ei)
 	}
+	if !cmpZKInputs {
+		return nil, exitInfos, nil
+	}
+
+	// compute last ZKInputs parameters
+	s.zki.OldLastIdx = (s.idx - 1).BigInt()
+	s.zki.OldStateRoot = s.mt.Root().BigInt()
+	s.zki.GlobalChainID = big.NewInt(0) // TODO, 0: ethereum, get this from config file
+	// zki.FeeIdxs = ? // TODO, this will be get from the config file
+	tokenIDs, err := s.getTokenIDsBigInt(l1usertxs, l1coordinatortxs, l2txs)
+	if err != nil {
+		return nil, nil, err
+	}
+	s.zki.FeePlanTokens = tokenIDs
+
+	// s.zki.ISInitStateRootFee = s.mt.Root().BigInt()
+	// compute fees
+
+	// once fees are computed
 
 	// return exitInfos, so Synchronizer will be able to store it into
 	// HistoryDB for the concrete BatchNum
-	return nil, exitInfos, nil
+	return s.zki, exitInfos, nil
+}
+
+// getTokenIDsBigInt returns the list of TokenIDs in *big.Int format
+func (s *StateDB) getTokenIDsBigInt(l1usertxs, l1coordinatortxs []*common.L1Tx, l2txs []*common.PoolL2Tx) ([]*big.Int, error) {
+	tokenIDs := make(map[common.TokenID]bool)
+	for i := 0; i < len(l1usertxs); i++ {
+		tokenIDs[l1usertxs[i].TokenID] = true
+	}
+	for i := 0; i < len(l1coordinatortxs); i++ {
+		tokenIDs[l1coordinatortxs[i].TokenID] = true
+	}
+	for i := 0; i < len(l2txs); i++ {
+		// as L2Tx does not have parameter TokenID, get it from the
+		// AccountsDB (in the StateDB)
+		acc, err := s.GetAccount(l2txs[i].ToIdx)
+		if err != nil {
+			return nil, err
+		}
+		tokenIDs[acc.TokenID] = true
+	}
+	var tBI []*big.Int
+	for t := range tokenIDs {
+		tBI = append(tBI, t.BigInt())
+	}
+	return tBI, nil
 }
 
 // processL1Tx process the given L1Tx applying the needed updates to the
 // StateDB depending on the transaction Type.
 func (s *StateDB) processL1Tx(exitTree *merkletree.MerkleTree, tx *common.L1Tx) (*common.Idx, *common.Account, error) {
+	// ZKInputs
+	if s.zki != nil {
+		// Txs
+		// s.zki.TxCompressedData[s.i] = tx.TxCompressedData() // uncomment once L1Tx.TxCompressedData is ready
+		s.zki.FromIdx[s.i] = tx.FromIdx.BigInt()
+		s.zki.ToIdx[s.i] = tx.ToIdx.BigInt()
+		s.zki.OnChain[s.i] = big.NewInt(1)
+
+		// L1Txs
+		s.zki.LoadAmountF[s.i] = tx.LoadAmount
+		s.zki.FromEthAddr[s.i] = common.EthAddrToBigInt(tx.FromEthAddr)
+		if tx.FromBJJ != nil {
+			s.zki.FromBJJCompressed[s.i] = common.BJJCompressedTo256BigInts(tx.FromBJJ.Compress())
+		}
+
+		// Intermediate States
+		s.zki.ISOnChain[s.i] = big.NewInt(1)
+	}
+
 	switch tx.Type {
 	case common.TxTypeForceTransfer, common.TxTypeTransfer:
 		// go to the MT account of sender and receiver, and update balance
@@ -116,6 +216,11 @@ err := s.applyCreateAccount(tx)
 		if err != nil {
 			return nil, nil, err
 		}
+
+		if s.zki != nil {
+			s.zki.AuxFromIdx[s.i] = s.idx.BigInt() // last s.idx is the one used for creating the new account
+			s.zki.NewAccount[s.i] = big.NewInt(1)
+		}
 	case common.TxTypeDeposit:
 		// update balance of the MT account
 		err := s.applyDeposit(tx, false)
@@ -140,6 +245,11 @@ err = s.applyTransfer(tx.Tx())
 		if err != nil {
 			return nil, nil, err
 		}
+
+		if s.zki != nil {
+			s.zki.AuxFromIdx[s.i] = s.idx.BigInt() // last s.idx is the one used for creating the new account
+			s.zki.NewAccount[s.i] = big.NewInt(1)
+		}
 	case common.TxTypeExit:
 		// execute exit flow
 		exitAccount, err := s.applyExit(exitTree, tx.Tx())
@@ -155,7 +265,48 @@ }
 
 // processL2Tx process the given L2Tx applying the needed updates to
 // the StateDB depending on the transaction Type.
-func (s *StateDB) processL2Tx(exitTree *merkletree.MerkleTree, tx *common.L2Tx) (*common.Idx, *common.Account, error) {
+func (s *StateDB) processL2Tx(exitTree *merkletree.MerkleTree, tx *common.PoolL2Tx) (*common.Idx, *common.Account, error) {
+	// ZKInputs
+	if s.zki != nil {
+		// Txs
+		// s.zki.TxCompressedData[s.i] = tx.TxCompressedData() // uncomment once L1Tx.TxCompressedData is ready
+		// s.zki.TxCompressedDataV2[s.i] = tx.TxCompressedDataV2() // uncomment once L2Tx.TxCompressedDataV2 is ready
+		s.zki.FromIdx[s.i] = tx.FromIdx.BigInt()
+		s.zki.ToIdx[s.i] = tx.ToIdx.BigInt()
+
+		// fill AuxToIdx if needed
+		if tx.ToIdx == common.Idx(0) {
+			// Idx not set in the Tx, get it from DB through ToEthAddr or ToBJJ
+			var idx common.Idx
+			if !bytes.Equal(tx.ToEthAddr.Bytes(), ffAddr.Bytes()) {
+				idx = s.getIdxByEthAddr(tx.ToEthAddr)
+				if idx == common.Idx(0) {
+					return nil, nil, fmt.Errorf("Idx can not be found for given tx.FromEthAddr")
+				}
+			} else {
+				idx = s.getIdxByBJJ(tx.ToBJJ)
+				if idx == common.Idx(0) {
+					return nil, nil, fmt.Errorf("Idx can not be found for given tx.FromBJJ")
+				}
+			}
+			s.zki.AuxToIdx[s.i] = idx.BigInt()
+		}
+		s.zki.ToBJJAy[s.i] = tx.ToBJJ.Y
+		s.zki.ToEthAddr[s.i] = common.EthAddrToBigInt(tx.ToEthAddr)
+
+		s.zki.OnChain[s.i] = big.NewInt(0)
+		s.zki.NewAccount[s.i] = big.NewInt(0)
+
+		// L2Txs
+		// s.zki.RqOffset[s.i] =  // TODO
+		// s.zki.RqTxCompressedDataV2[s.i] = // TODO
+		// s.zki.RqToEthAddr[s.i] = common.EthAddrToBigInt(tx.RqToEthAddr) // TODO
+		// s.zki.RqToBJJAy[s.i] = tx.ToBJJ.Y // TODO
+		s.zki.S[s.i] = tx.Signature.S
+		s.zki.R8x[s.i] = tx.Signature.R8.X
+		s.zki.R8y[s.i] = tx.Signature.R8.Y
+	}
+
 	switch tx.Type {
 	case common.TxTypeTransfer:
 		// go to the MT account of sender and receiver, and update

@@ -1,6 +1,8 @@
 package statedb
 
 import (
+	"encoding/json"
+	"fmt"
 	"io/ioutil"
 	"strings"
 	"testing"
@@ -10,6 +12,8 @@ "github.com/hermeznetwork/hermez-node/test"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
+
+var debug = false
 
 func TestProcessTxs(t *testing.T) {
 	dir, err := ioutil.TempDir("", "tmpdb")
@@ -30,9 +34,9 @@ assert.Equal(t, 21, len(poolL2Txs[0]))
 
 	// iterate for each batch
 	for i := 0; i < len(l1Txs); i++ {
-		l2Txs := common.PoolL2TxsToL2Txs(poolL2Txs[i])
+		// l2Txs := common.PoolL2TxsToL2Txs(poolL2Txs[i])
 
-		_, _, err := sdb.ProcessTxs(true, l1Txs[i], coordinatorL1Txs[i], l2Txs)
+		_, _, err := sdb.ProcessTxs(true, true, l1Txs[i], coordinatorL1Txs[i], poolL2Txs[i])
 		require.Nil(t, err)
 	}
 
@@ -65,8 +69,8 @@ assert.Equal(t, 0, len(coordinatorL1Txs[2]))
 	assert.Equal(t, 7, len(poolL2Txs[2]))
 
 	// use first batch
-	l2txs := common.PoolL2TxsToL2Txs(poolL2Txs[0])
-	_, exitInfos, err := sdb.ProcessTxs(true, l1Txs[0], coordinatorL1Txs[0], l2txs)
+	// l2txs := common.PoolL2TxsToL2Txs(poolL2Txs[0])
+	_, exitInfos, err := sdb.ProcessTxs(true, true, l1Txs[0], coordinatorL1Txs[0], poolL2Txs[0])
 	require.Nil(t, err)
 	assert.Equal(t, 0, len(exitInfos))
 	acc, err := sdb.GetAccount(common.Idx(1))
@@ -74,8 +78,8 @@ assert.Nil(t, err)
 	assert.Equal(t, "28", acc.Balance.String())
 
 	// use second batch
-	l2txs = common.PoolL2TxsToL2Txs(poolL2Txs[1])
-	_, exitInfos, err = sdb.ProcessTxs(true, l1Txs[1], coordinatorL1Txs[1], l2txs)
+	// l2txs = common.PoolL2TxsToL2Txs(poolL2Txs[1])
+	_, exitInfos, err = sdb.ProcessTxs(true, true, l1Txs[1], coordinatorL1Txs[1], poolL2Txs[1])
 	require.Nil(t, err)
 	assert.Equal(t, 5, len(exitInfos))
 	acc, err = sdb.GetAccount(common.Idx(1))
@@ -83,11 +87,38 @@ assert.Nil(t, err)
 	assert.Equal(t, "48", acc.Balance.String())
 
 	// use third batch
-	l2txs = common.PoolL2TxsToL2Txs(poolL2Txs[2])
-	_, exitInfos, err = sdb.ProcessTxs(true, l1Txs[2], coordinatorL1Txs[2], l2txs)
+	// l2txs = common.PoolL2TxsToL2Txs(poolL2Txs[2])
+	_, exitInfos, err = sdb.ProcessTxs(true, true, l1Txs[2], coordinatorL1Txs[2], poolL2Txs[2])
 	require.Nil(t, err)
 	assert.Equal(t, 1, len(exitInfos))
 	acc, err = sdb.GetAccount(common.Idx(1))
 	assert.Nil(t, err)
 	assert.Equal(t, "23", acc.Balance.String())
 }
+
+func TestZKInputsGeneration(t *testing.T) {
+	dir, err := ioutil.TempDir("", "tmpdb")
+	require.Nil(t, err)
+
+	sdb, err := NewStateDB(dir, true, 32)
+	assert.Nil(t, err)
+
+	// generate test transactions from test.SetTest0 code
+	parser := test.NewParser(strings.NewReader(test.SetTest0))
+	instructions, err := parser.Parse()
+	assert.Nil(t, err)
+
+	l1Txs, coordinatorL1Txs, poolL2Txs := test.GenerateTestTxs(t, instructions)
+	assert.Equal(t, 29, len(l1Txs[0]))
+	assert.Equal(t, 0, len(coordinatorL1Txs[0]))
+	assert.Equal(t, 21, len(poolL2Txs[0]))
+
+	zki, _, err := sdb.ProcessTxs(false, true, l1Txs[0], coordinatorL1Txs[0], poolL2Txs[0])
+	require.Nil(t, err)
+
+	s, err := json.Marshal(zki)
+	require.Nil(t, err)
+	if debug {
+		fmt.Println(string(s))
+	}
+}

@@ -0,0 +1,17 @@
+package statedb
+
+import (
+	ethCommon "github.com/ethereum/go-ethereum/common"
+	"github.com/hermeznetwork/hermez-node/common"
+	"github.com/iden3/go-iden3-crypto/babyjub"
+)
+
+// TODO
+func (s *StateDB) getIdxByEthAddr(addr ethCommon.Address) common.Idx {
+	return common.Idx(0)
+}
+
+// TODO
+func (s *StateDB) getIdxByBJJ(pk *babyjub.PublicKey) common.Idx {
+	return common.Idx(0)
+}