Merge pull request #265 from hermeznetwork/feature/zkinputs1

StateDB group Fee txs and ZKInputs gen of Fee txs & Update tx bytes parsers methods

common/fee_test.go

@@ -48,8 +48,11 @@ func TestCalcFeeAmount(t *testing.T) {
 }
 
 func TestFeePrintSQLSwitch(t *testing.T) {
+	debug := false
 	for i := 0; i < 256; i++ {
 		f := FeeSelector(i).Percentage()
+		if debug {
 			fmt.Printf("        WHEN $1 = %03d THEN %.6e\n", i, f)
 		}
+	}
 }

common/l1tx.go

@@ -146,8 +146,11 @@ func (tx L1Tx) Tx() Tx {
 	return genericTx
 }
 
-// BytesUser encodes a L1Tx into []byte
-func (tx *L1Tx) BytesUser() ([]byte, error) {
+// BytesGeneric returns the generic representation of a L1Tx. This method is
+// used to compute the []byte representation of a L1UserTx, and also to compute
+// the L1TxData for the ZKInputs (at the HashGlobalInputs), using this method
+// for L1CoordinatorTxs & L1UserTxs (for the ZKInputs case).
+func (tx *L1Tx) BytesGeneric() ([]byte, error) {
 	var b [L1UserTxBytesLen]byte
 	copy(b[0:20], tx.FromEthAddr.Bytes())
 	pkCompL := tx.FromBJJ.Compress()
@@ -177,8 +180,19 @@ func (tx *L1Tx) BytesUser() ([]byte, error) {
 	return b[:], nil
 }
 
+// BytesUser encodes a L1UserTx into []byte
+func (tx *L1Tx) BytesUser() ([]byte, error) {
+	if !tx.UserOrigin {
+		return nil, fmt.Errorf("Can not calculate BytesUser() for a L1CoordinatorTx")
+	}
+	return tx.BytesGeneric()
+}
+
 // BytesCoordinatorTx encodes a L1CoordinatorTx into []byte
 func (tx *L1Tx) BytesCoordinatorTx(compressedSignatureBytes []byte) ([]byte, error) {
+	if tx.UserOrigin {
+		return nil, fmt.Errorf("Can not calculate BytesCoordinatorTx() for a L1UserTx")
+	}
 	var b [L1CoordinatorTxBytesLen]byte
 	v := compressedSignatureBytes[64]
 	s := compressedSignatureBytes[32:64]
@@ -210,7 +224,6 @@ func L1UserTxFromBytes(b []byte) (*L1Tx, error) {
 	var pkComp babyjub.PublicKeyComp
 	copy(pkComp[:], pkCompL)
 	tx.FromBJJ, err = pkComp.Decompress()
-
 	if err != nil {
 		return nil, err
 	}

common/l1tx_test.go

@@ -109,6 +109,7 @@ func TestL1TxByteParsersCompatibility(t *testing.T) {
 		FromIdx:     Idx(29767899),
 		FromBJJ:     pk,
 		FromEthAddr: ethCommon.HexToAddress("0x85dab5b9e2e361d0c208d77be90efcc0439b0a53"),
+		UserOrigin:  true,
 	}
 
 	expected, err := utils.HexDecode("85dab5b9e2e361d0c208d77be90efcc0439b0a530dd02deb2c81068e7a0f7e327df80b4ab79ee1f41a7def613e73a20c32eece5a000001c638db8be880f00020039c0000053cb88d")

common/l2tx.go

@@ -105,49 +105,54 @@ func L2TxsToPoolL2Txs(txs []L2Tx) []PoolL2Tx {
 
 // Bytes encodes a L2Tx into []byte
 func (tx *L2Tx) Bytes(nLevels int) ([]byte, error) {
-	fromIdxNumBytes := nLevels / 8 //nolint:gomnd
-	toIdxNumBytes := nLevels / 8   //nolint:gomnd
-	var b []byte
+	idxLen := nLevels / 8 //nolint:gomnd
+
+	b := make([]byte, ((nLevels*2)+16+8)/8) //nolint:gomnd
+
 	fromIdxBytes, err := tx.FromIdx.Bytes()
 	if err != nil {
 		return nil, err
 	}
-	b = append(b, fromIdxBytes[6-fromIdxNumBytes:]...)
+	copy(b[0:idxLen], fromIdxBytes[6-idxLen:]) // [6-idxLen:] as is BigEndian
+
 	toIdxBytes, err := tx.ToIdx.Bytes()
 	if err != nil {
 		return nil, err
 	}
-	b = append(b, toIdxBytes[6-toIdxNumBytes:]...)
+	copy(b[idxLen:idxLen*2], toIdxBytes[6-idxLen:])
+
 	amountFloat16, err := NewFloat16(tx.Amount)
 	if err != nil {
 		return nil, err
 	}
-	b = append(b, amountFloat16.Bytes()...)
-	b = append(b, byte(tx.Fee))
+
+	copy(b[idxLen*2:idxLen*2+2], amountFloat16.Bytes())
+	b[idxLen*2+2] = byte(tx.Fee)
+
 	return b[:], nil
 }
 
 // L2TxFromBytes decodes a L1Tx from []byte
 func L2TxFromBytes(b []byte, nLevels int) (*L2Tx, error) {
-	fromIdxNumByte := nLevels / 8              //nolint:gomnd
-	toIdxNumByte := fromIdxNumByte + nLevels/8 //nolint:gomnd
-	amountLenBytes := 2
-	amountNumByte := toIdxNumByte + amountLenBytes
+	idxLen := nLevels / 8 //nolint:gomnd
 	tx := &L2Tx{}
 	var err error
+
 	var paddedFromIdxBytes [6]byte
-	copy(paddedFromIdxBytes[6-len(b[0:fromIdxNumByte]):], b[0:fromIdxNumByte])
+	copy(paddedFromIdxBytes[6-idxLen:], b[0:idxLen])
 	tx.FromIdx, err = IdxFromBytes(paddedFromIdxBytes[:])
 	if err != nil {
 		return nil, err
 	}
+
 	var paddedToIdxBytes [6]byte
-	copy(paddedToIdxBytes[6-len(b[fromIdxNumByte:toIdxNumByte]):6], b[fromIdxNumByte:toIdxNumByte])
+	copy(paddedToIdxBytes[6-idxLen:6], b[idxLen:idxLen*2])
 	tx.ToIdx, err = IdxFromBytes(paddedToIdxBytes[:])
 	if err != nil {
 		return nil, err
 	}
-	tx.Amount = Float16FromBytes(b[toIdxNumByte:amountNumByte]).BigInt()
-	tx.Fee = FeeSelector(b[amountNumByte])
+
+	tx.Amount = Float16FromBytes(b[idxLen*2 : idxLen*2+2]).BigInt()
+	tx.Fee = FeeSelector(b[idxLen*2+2])
 	return tx, nil
 }

common/zk.go

@@ -1,6 +1,5 @@
 // Package common contains all the common data structures used at the
 // hermez-node, zk.go contains the zkSnark inputs used to generate the proof
-//nolint:deadcode,structcheck,unused
 package common
 
 import (
@@ -11,21 +10,30 @@ import (
 	"github.com/mitchellh/mapstructure"
 )
 
-// circuit parameters
-// absolute maximum of L1 or L2 transactions allowed
-type nTx uint32
+// ZKMetadata contains ZKInputs metadata that is not used directly in the
+// ZKInputs result, but to calculate values for Hash check
+type ZKMetadata struct {
+	// Circuit parameters
+	// absolute maximum of L1 or L2 transactions allowed
+	NTx uint32
+	// merkle tree depth
+	NLevels   uint32
+	MaxLevels uint32
+	// absolute maximum of L1 transaction allowed
+	MaxL1Tx uint32
+	// Maximum number of Idxs where Fees can be send in a batch (currently
+	// is constant for all circuits: 64)
+	MaxFeeIdxs uint32
 
-// merkle tree depth
-type nLevels uint32
-
-// absolute maximum of L1 transaction allowed
-type maxL1Tx uint32
-
-//absolute maximum of fee transactions allowed
-type maxFeeTx uint32
+	L1TxsData [][]byte
+	L2TxsData [][]byte
+	ChainID   uint16
+}
 
 // ZKInputs represents the inputs that will be used to generate the zkSNARK proof
 type ZKInputs struct {
+	Metadata ZKMetadata
+
 	//
 	// General
 	//
@@ -38,11 +46,11 @@ type ZKInputs struct {
 	// GlobalChainID is the blockchain ID (0 for Ethereum mainnet). This value can be get from the smart contract.
 	GlobalChainID *big.Int `json:"globalChainID"` // uint16
 	// FeeIdxs is an array of merkle tree indexes where the coordinator will receive the accumulated fees
-	FeeIdxs []*big.Int `json:"feeIdxs"` // uint64 (max nLevels bits), len: [maxFeeTx]
+	FeeIdxs []*big.Int `json:"feeIdxs"` // uint64 (max nLevels bits), len: [maxFeeIdxs]
 
 	// accumulate fees
 	// FeePlanTokens contains all the tokenIDs for which the fees are being accumulated
-	FeePlanTokens []*big.Int `json:"feePlanTokens"` // uint32 (max 32 bits), len: [maxFeeTx]
+	FeePlanTokens []*big.Int `json:"feePlanTokens"` // uint32 (max 32 bits), len: [maxFeeIdxs]
 
 	//
 	// Txs (L1&L2)
@@ -142,13 +150,13 @@ type ZKInputs struct {
 	// state 3, value of the account leaf receiver of the Fees
 	// fee tx
 	// State fees
-	TokenID3  []*big.Int   `json:"tokenID3"`  // uint32, len: [maxFeeTx]
-	Nonce3    []*big.Int   `json:"nonce3"`    // uint64 (max 40 bits), len: [maxFeeTx]
-	Sign3     []*big.Int   `json:"sign3"`     // bool, len: [maxFeeTx]
-	Ay3       []*big.Int   `json:"ay3"`       // big.Int, len: [maxFeeTx]
-	Balance3  []*big.Int   `json:"balance3"`  // big.Int (max 192 bits), len: [maxFeeTx]
-	EthAddr3  []*big.Int   `json:"ethAddr3"`  // ethCommon.Address, len: [maxFeeTx]
-	Siblings3 [][]*big.Int `json:"siblings3"` // Hash, len: [maxFeeTx][nLevels + 1]
+	TokenID3  []*big.Int   `json:"tokenID3"`  // uint32, len: [maxFeeIdxs]
+	Nonce3    []*big.Int   `json:"nonce3"`    // uint64 (max 40 bits), len: [maxFeeIdxs]
+	Sign3     []*big.Int   `json:"sign3"`     // bool, len: [maxFeeIdxs]
+	Ay3       []*big.Int   `json:"ay3"`       // big.Int, len: [maxFeeIdxs]
+	Balance3  []*big.Int   `json:"balance3"`  // big.Int (max 192 bits), len: [maxFeeIdxs]
+	EthAddr3  []*big.Int   `json:"ethAddr3"`  // ethCommon.Address, len: [maxFeeIdxs]
+	Siblings3 [][]*big.Int `json:"siblings3"` // Hash, len: [maxFeeIdxs][nLevels + 1]
 
 	//
 	// Intermediate States
@@ -174,14 +182,14 @@ type ZKInputs struct {
 	// ISExitTree root at the moment of the Tx the value once the Tx is processed into the exit tree
 	ISExitRoot []*big.Int `json:"imExitRoot"` // Hash, len: [nTx - 1]
 	// ISAccFeeOut accumulated fees once the Tx is processed
-	ISAccFeeOut [][]*big.Int `json:"imAccFeeOut"` // big.Int, len: [nTx - 1][maxFeeTx]
+	ISAccFeeOut [][]*big.Int `json:"imAccFeeOut"` // big.Int, len: [nTx - 1][maxFeeIdxs]
 	// fee-tx
 	// ISStateRootFee root at the moment of the Tx, the state root value once the Tx is processed into the state tree
-	ISStateRootFee []*big.Int `json:"imStateRootFee"` // Hash, len: [maxFeeTx - 1]
+	ISStateRootFee []*big.Int `json:"imStateRootFee"` // Hash, len: [maxFeeIdxs - 1]
 	// ISInitStateRootFee state root once all L1-L2 tx are processed (before computing the fees-tx)
 	ISInitStateRootFee *big.Int `json:"imInitStateRootFee"` // Hash
 	// ISFinalAccFee final accumulated fees (before computing the fees-tx)
-	ISFinalAccFee []*big.Int `json:"imFinalAccFee"` // big.Int, len: [maxFeeTx - 1]
+	ISFinalAccFee []*big.Int `json:"imFinalAccFee"` // big.Int, len: [maxFeeIdxs - 1]
 }
 
 func bigIntsToStrings(v interface{}) interface{} {
@@ -212,6 +220,8 @@ func bigIntsToStrings(v interface{}) interface{} {
 			r[i] = bigIntsToStrings(c[i])
 		}
 		return r
+	case map[string]interface{}:
+		// avoid printing a warning when there is a struct type
 	default:
 		log.Warnf("bigIntsToStrings unexpected type: %T\n", v)
 	}
@@ -240,15 +250,18 @@ func (z ZKInputs) MarshalJSON() ([]byte, error) {
 }
 
 // NewZKInputs returns a pointer to an initialized struct of ZKInputs
-func NewZKInputs(nTx, maxFeeTx, nLevels int) *ZKInputs {
+func NewZKInputs(nTx, maxFeeIdxs, nLevels int) *ZKInputs {
 	zki := &ZKInputs{}
+	zki.Metadata.NTx = uint32(nTx)
+	zki.Metadata.MaxFeeIdxs = uint32(maxFeeIdxs)
+	zki.Metadata.NLevels = uint32(nLevels)
 
 	// General
 	zki.OldLastIdx = big.NewInt(0)
 	zki.OldStateRoot = big.NewInt(0)
 	zki.GlobalChainID = big.NewInt(0)
-	zki.FeeIdxs = newSlice(maxFeeTx)
-	zki.FeePlanTokens = newSlice(maxFeeTx)
+	zki.FeeIdxs = newSlice(maxFeeIdxs)
+	zki.FeePlanTokens = newSlice(maxFeeIdxs)
 
 	// Txs
 	zki.TxCompressedData = newSlice(nTx)
@@ -312,13 +325,13 @@ func NewZKInputs(nTx, maxFeeTx, nLevels int) *ZKInputs {
 	zki.OldKey2 = newSlice(nTx)
 	zki.OldValue2 = newSlice(nTx)
 
-	zki.TokenID3 = newSlice(maxFeeTx)
-	zki.Nonce3 = newSlice(maxFeeTx)
-	zki.Sign3 = newSlice(maxFeeTx)
-	zki.Ay3 = newSlice(maxFeeTx)
-	zki.Balance3 = newSlice(maxFeeTx)
-	zki.EthAddr3 = newSlice(maxFeeTx)
-	zki.Siblings3 = make([][]*big.Int, maxFeeTx)
+	zki.TokenID3 = newSlice(maxFeeIdxs)
+	zki.Nonce3 = newSlice(maxFeeIdxs)
+	zki.Sign3 = newSlice(maxFeeIdxs)
+	zki.Ay3 = newSlice(maxFeeIdxs)
+	zki.Balance3 = newSlice(maxFeeIdxs)
+	zki.EthAddr3 = newSlice(maxFeeIdxs)
+	zki.Siblings3 = make([][]*big.Int, maxFeeIdxs)
 	for i := 0; i < len(zki.Siblings3); i++ {
 		zki.Siblings3[i] = newSlice(nLevels + 1)
 	}
@@ -330,11 +343,11 @@ func NewZKInputs(nTx, maxFeeTx, nLevels int) *ZKInputs {
 	zki.ISExitRoot = newSlice(nTx - 1)
 	zki.ISAccFeeOut = make([][]*big.Int, nTx-1)
 	for i := 0; i < len(zki.ISAccFeeOut); i++ {
-		zki.ISAccFeeOut[i] = newSlice(maxFeeTx)
+		zki.ISAccFeeOut[i] = newSlice(maxFeeIdxs)
 	}
-	zki.ISStateRootFee = newSlice(maxFeeTx - 1)
+	zki.ISStateRootFee = newSlice(maxFeeIdxs - 1)
 	zki.ISInitStateRootFee = big.NewInt(0)
-	zki.ISFinalAccFee = newSlice(maxFeeTx - 1)
+	zki.ISFinalAccFee = newSlice(maxFeeIdxs - 1)
 
 	return zki
 }

db/statedb/statedb.go

@@ -78,7 +78,11 @@ type StateDB struct {
 	// idx holds the current Idx that the BatchBuilder is using
 	idx common.Idx
 	zki *common.ZKInputs
-	i   int // i is the current transaction index in the ZKInputs generation (zki)
+	// i is the current transaction index in the ZKInputs generation (zki)
+	i int
+	// accumulatedFees contains the accumulated fees for each token (Coord
+	// Idx) in the processed batch
+	accumulatedFees map[common.Idx]*big.Int
 }
 
 // NewStateDB creates a new StateDB, allowing to use an in-memory or in-disk

db/statedb/txprocessors.go

@@ -64,6 +64,8 @@ func (s *StateDB) ProcessTxs(coordIdxs []common.Idx, l1usertxs, l1coordinatortxs
 	}
 	defer s.resetZKInputs()
 
+	s.accumulatedFees = make(map[common.Idx]*big.Int)
+
 	nTx := len(l1usertxs) + len(l1coordinatortxs) + len(l2txs)
 	if nTx == 0 {
 		// TODO return ZKInputs of batch without txs
@@ -77,22 +79,8 @@ func (s *StateDB) ProcessTxs(coordIdxs []common.Idx, l1usertxs, l1coordinatortxs
 	}
 	exits := make([]processedExit, nTx)
 
-	// get TokenIDs of coordIdxs
-	coordIdxsMap, err := s.getTokenIDsFromIdxs(coordIdxs)
-	if err != nil {
-		return nil, err
-	}
-
-	var collectedFees map[common.TokenID]*big.Int
-	if s.typ == TypeSynchronizer {
-		collectedFees = make(map[common.TokenID]*big.Int)
-		for tokenID := range coordIdxsMap {
-			collectedFees[tokenID] = big.NewInt(0)
-		}
-	}
-
 	if s.typ == TypeBatchBuilder {
-		maxFeeTx := 2 // TODO this value will be a parameter
+		maxFeeTx := 64 // TODO this value will be a parameter
 		s.zki = common.NewZKInputs(nTx, maxFeeTx, s.mt.MaxLevels())
 		s.zki.OldLastIdx = (s.idx - 1).BigInt()
 		s.zki.OldStateRoot = s.mt.Root().BigInt()
@@ -120,8 +108,9 @@ func (s *StateDB) ProcessTxs(coordIdxs []common.Idx, l1usertxs, l1coordinatortxs
 		}
 	}
 
-	// assumption: l1usertx are sorted by L1Tx.Position
+	// Process L1UserTxs
 	for i := 0; i < len(l1usertxs); i++ {
+		// assumption: l1usertx are sorted by L1Tx.Position
 		exitIdx, exitAccount, newExit, createdAccount, err := s.processL1Tx(exitTree, &l1usertxs[i])
 		if err != nil {
 			return nil, err
@@ -140,7 +129,17 @@ func (s *StateDB) ProcessTxs(coordIdxs []common.Idx, l1usertxs, l1coordinatortxs
 		if s.typ == TypeSynchronizer && createdAccount != nil {
 			createdAccounts = append(createdAccounts, *createdAccount)
 		}
+
+		if s.zki != nil {
+			l1TxData, err := l1usertxs[i].BytesGeneric()
+			if err != nil {
+				return nil, err
 			}
+			s.zki.Metadata.L1TxsData = append(s.zki.Metadata.L1TxsData, l1TxData)
+		}
+	}
+
+	// Process L1CoordinatorTxs
 	for i := 0; i < len(l1coordinatortxs); i++ {
 		exitIdx, _, _, createdAccount, err := s.processL1Tx(exitTree, &l1coordinatortxs[i])
 		if err != nil {
@@ -152,7 +151,36 @@ func (s *StateDB) ProcessTxs(coordIdxs []common.Idx, l1usertxs, l1coordinatortxs
 		if s.typ == TypeSynchronizer && createdAccount != nil {
 			createdAccounts = append(createdAccounts, *createdAccount)
 		}
+		if s.zki != nil {
+			l1TxData, err := l1coordinatortxs[i].BytesGeneric()
+			if err != nil {
+				return nil, err
 			}
+			s.zki.Metadata.L1TxsData = append(s.zki.Metadata.L1TxsData, l1TxData)
+		}
+	}
+
+	s.accumulatedFees = make(map[common.Idx]*big.Int)
+	for _, idx := range coordIdxs {
+		s.accumulatedFees[idx] = big.NewInt(0)
+	}
+
+	// once L1UserTxs & L1CoordinatorTxs are processed, get TokenIDs of
+	// coordIdxs. In this way, if a coordIdx uses an Idx that is being
+	// created in the current batch, at this point the Idx will be created
+	coordIdxsMap, err := s.getTokenIDsFromIdxs(coordIdxs)
+	if err != nil {
+		return nil, err
+	}
+	var collectedFees map[common.TokenID]*big.Int
+	if s.typ == TypeSynchronizer {
+		collectedFees = make(map[common.TokenID]*big.Int)
+		for tokenID := range coordIdxsMap {
+			collectedFees[tokenID] = big.NewInt(0)
+		}
+	}
+
+	// Process L2Txs
 	for i := 0; i < len(l2txs); i++ {
 		exitIdx, exitAccount, newExit, err := s.processL2Tx(coordIdxsMap, collectedFees, exitTree, &l2txs[i])
 		if err != nil {
@@ -171,6 +199,39 @@ func (s *StateDB) ProcessTxs(coordIdxs []common.Idx, l1usertxs, l1coordinatortxs
 		}
 	}
 
+	// distribute the AccumulatedFees from the processed L2Txs into the
+	// Coordinator Idxs
+	iFee := 0
+	for idx, accumulatedFee := range s.accumulatedFees {
+		// send the fee to the Idx of the Coordinator for the TokenID
+		accCoord, err := s.GetAccount(idx)
+		if err != nil {
+			log.Errorw("Can not distribute accumulated fees to coordinator account: No coord Idx to receive fee", "idx", idx)
+			return nil, err
+		}
+		accCoord.Balance = new(big.Int).Add(accCoord.Balance, accumulatedFee)
+		pFee, err := s.UpdateAccount(idx, accCoord)
+		if err != nil {
+			log.Error(err)
+			return nil, err
+		}
+		if s.zki != nil {
+			s.zki.TokenID3[iFee] = accCoord.TokenID.BigInt()
+			s.zki.Nonce3[iFee] = accCoord.Nonce.BigInt()
+			if babyjub.PointCoordSign(accCoord.PublicKey.X) {
+				s.zki.Sign3[iFee] = big.NewInt(1)
+			}
+			s.zki.Ay3[iFee] = accCoord.PublicKey.Y
+			s.zki.Balance3[iFee] = accCoord.Balance
+			s.zki.EthAddr3[iFee] = common.EthAddrToBigInt(accCoord.EthAddr)
+			s.zki.Siblings3[iFee] = siblingsToZKInputFormat(pFee.Siblings)
+
+			// add Coord Idx to ZKInputs.FeeTxsData
+			s.zki.FeeIdxs[iFee] = idx.BigInt()
+		}
+		iFee++
+	}
+
 	if s.typ == TypeTxSelector {
 		return nil, nil
 	}
@@ -178,7 +239,6 @@ func (s *StateDB) ProcessTxs(coordIdxs []common.Idx, l1usertxs, l1coordinatortxs
 	// once all txs processed (exitTree root frozen), for each Exit,
 	// generate common.ExitInfo data
 	var exitInfos []common.ExitInfo
-	// exitInfos := []common.ExitInfo{}
 	for i := 0; i < nTx; i++ {
 		if !exits[i].exit {
 			continue
@@ -245,9 +305,6 @@ func (s *StateDB) ProcessTxs(coordIdxs []common.Idx, l1usertxs, l1coordinatortxs
 
 	// s.zki.ISInitStateRootFee = s.mt.Root().BigInt()
 
-	// TODO once the Node Config sets the Accounts where to send the Fees
-	// compute fees & update ZKInputs
-
 	// return ZKInputs as the BatchBuilder will return it to forge the Batch
 	return &ProcessTxOutput{
 		ZKInputs:           s.zki,
@@ -606,10 +663,10 @@ func (s *StateDB) applyTransfer(coordIdxsMap map[common.TokenID]common.Idx, coll
 		return err
 	}
 
+	if !tx.IsL1 {
 		// increment nonce
 		accSender.Nonce++
 
-	if !tx.IsL1 {
 		// compute fee and subtract it from the accSender
 		fee, err := common.CalcFeeAmount(tx.Amount, *tx.Fee)
 		if err != nil {
@@ -618,19 +675,16 @@ func (s *StateDB) applyTransfer(coordIdxsMap map[common.TokenID]common.Idx, coll
 		feeAndAmount := new(big.Int).Add(tx.Amount, fee)
 		accSender.Balance = new(big.Int).Sub(accSender.Balance, feeAndAmount)
 
-		// send the fee to the Idx of the Coordinator for the TokenID
 		accCoord, err := s.GetAccount(coordIdxsMap[accSender.TokenID])
 		if err != nil {
 			log.Debugw("No coord Idx to receive fee", "tx", tx)
 		} else {
-			accCoord.Balance = new(big.Int).Add(accCoord.Balance, fee)
-			_, err = s.UpdateAccount(coordIdxsMap[accSender.TokenID], accCoord)
-			if err != nil {
-				log.Error(err)
-				return err
-			}
+			// accumulate the fee for the Coord account
+			accumulated := s.accumulatedFees[accCoord.Idx]
+			accumulated.Add(accumulated, fee)
+
 			if s.typ == TypeSynchronizer {
-				collected := collectedFees[accSender.TokenID]
+				collected := collectedFees[accCoord.TokenID]
 				collected.Add(collected, fee)
 			}
 		}
@@ -753,6 +807,9 @@ func (s *StateDB) applyExit(coordIdxsMap map[common.TokenID]common.Idx, collecte
 	}
 
 	if !tx.IsL1 {
+		// increment nonce
+		acc.Nonce++
+
 		// compute fee and subtract it from the accSender
 		fee, err := common.CalcFeeAmount(tx.Amount, *tx.Fee)
 		if err != nil {
@@ -761,19 +818,16 @@ func (s *StateDB) applyExit(coordIdxsMap map[common.TokenID]common.Idx, collecte
 		feeAndAmount := new(big.Int).Add(tx.Amount, fee)
 		acc.Balance = new(big.Int).Sub(acc.Balance, feeAndAmount)
 
-		// send the fee to the Idx of the Coordinator for the TokenID
 		accCoord, err := s.GetAccount(coordIdxsMap[acc.TokenID])
 		if err != nil {
 			log.Debugw("No coord Idx to receive fee", "tx", tx)
 		} else {
-			accCoord.Balance = new(big.Int).Add(accCoord.Balance, fee)
-			_, err = s.UpdateAccount(coordIdxsMap[acc.TokenID], accCoord)
-			if err != nil {
-				log.Error(err)
-				return nil, false, err
-			}
+			// accumulate the fee for the Coord account
+			accumulated := s.accumulatedFees[accCoord.Idx]
+			accumulated.Add(accumulated, fee)
+
 			if s.typ == TypeSynchronizer {
-				collected := collectedFees[acc.TokenID]
+				collected := collectedFees[accCoord.TokenID]
 				collected.Add(collected, fee)
 			}
 		}