@@ -11,4 +11,20 @@ You must compile the contracts to get the `.bin` and `.abi` files. The contracts used are in the repo: https://github.com/hermeznetwork/contracts-circuits
 
 Specifically they have been processed in the commit with hash: `745e8d588496d7762d4084a54bafd4435061ae35`
 
-> abigen version 1.9.21+> abigen version 1.9.21
+
+---
+
+ERC20 go code was generated with the following command:
+```
+abigen --sol erc20.sol --pkg erc20 --out erc20/erc20.go
+```
+
+Versions:
+```
+ $ abigen --version
+abigen version 1.9.21-stable-0287d548
+ $ solc --version
+solc, the solidity compiler commandline interface
+Version: 0.7.1+commit.f4a555be.Linux.g++
+```

@@ -0,0 +1,19 @@
+pragma solidity ^0.7.0;
+
+contract ERC20 {
+    string public constant name = "";
+    string public constant symbol = "";
+    uint8 public constant decimals = 0;
+
+    /*
+    function totalSupply() public constant returns (uint);
+    function balanceOf(address tokenOwner) public constant returns (uint balance);
+    function allowance(address tokenOwner, address spender) public constant returns (uint remaining);
+    function transfer(address to, uint tokens) public returns (bool success);
+    function approve(address spender, uint tokens) public returns (bool success);
+    function transferFrom(address from, address to, uint tokens) public returns (bool success);
+
+    event Transfer(address indexed from, address indexed to, uint tokens);
+    event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
+    */
+}

@@ -0,0 +1,274 @@
+// Code generated - DO NOT EDIT.
+// This file is a generated binding and any manual changes will be lost.
+
+package erc20
+
+import (
+	"math/big"
+	"strings"
+
+	ethereum "github.com/ethereum/go-ethereum"
+	"github.com/ethereum/go-ethereum/accounts/abi"
+	"github.com/ethereum/go-ethereum/accounts/abi/bind"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/event"
+)
+
+// Reference imports to suppress errors if they are not otherwise used.
+var (
+	_ = big.NewInt
+	_ = strings.NewReader
+	_ = ethereum.NotFound
+	_ = bind.Bind
+	_ = common.Big1
+	_ = types.BloomLookup
+	_ = event.NewSubscription
+)
+
+// ERC20ABI is the input ABI used to generate the binding from.
+const ERC20ABI = "[{\"inputs\":[],\"name\":\"decimals\",\"outputs\":[{\"internalType\":\"uint8\",\"name\":\"\",\"type\":\"uint8\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[],\"name\":\"name\",\"outputs\":[{\"internalType\":\"string\",\"name\":\"\",\"type\":\"string\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[],\"name\":\"symbol\",\"outputs\":[{\"internalType\":\"string\",\"name\":\"\",\"type\":\"string\"}],\"stateMutability\":\"view\",\"type\":\"function\"}]"
+
+// ERC20FuncSigs maps the 4-byte function signature to its string representation.
+var ERC20FuncSigs = map[string]string{
+	"313ce567": "decimals()",
+	"06fdde03": "name()",
+	"95d89b41": "symbol()",
+}
+
+// ERC20Bin is the compiled bytecode used for deploying new contracts.
+var ERC20Bin = "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"
+
+// DeployERC20 deploys a new Ethereum contract, binding an instance of ERC20 to it.
+func DeployERC20(auth *bind.TransactOpts, backend bind.ContractBackend) (common.Address, *types.Transaction, *ERC20, error) {
+	parsed, err := abi.JSON(strings.NewReader(ERC20ABI))
+	if err != nil {
+		return common.Address{}, nil, nil, err
+	}
+
+	address, tx, contract, err := bind.DeployContract(auth, parsed, common.FromHex(ERC20Bin), backend)
+	if err != nil {
+		return common.Address{}, nil, nil, err
+	}
+	return address, tx, &ERC20{ERC20Caller: ERC20Caller{contract: contract}, ERC20Transactor: ERC20Transactor{contract: contract}, ERC20Filterer: ERC20Filterer{contract: contract}}, nil
+}
+
+// ERC20 is an auto generated Go binding around an Ethereum contract.
+type ERC20 struct {
+	ERC20Caller     // Read-only binding to the contract
+	ERC20Transactor // Write-only binding to the contract
+	ERC20Filterer   // Log filterer for contract events
+}
+
+// ERC20Caller is an auto generated read-only Go binding around an Ethereum contract.
+type ERC20Caller struct {
+	contract *bind.BoundContract // Generic contract wrapper for the low level calls
+}
+
+// ERC20Transactor is an auto generated write-only Go binding around an Ethereum contract.
+type ERC20Transactor struct {
+	contract *bind.BoundContract // Generic contract wrapper for the low level calls
+}
+
+// ERC20Filterer is an auto generated log filtering Go binding around an Ethereum contract events.
+type ERC20Filterer struct {
+	contract *bind.BoundContract // Generic contract wrapper for the low level calls
+}
+
+// ERC20Session is an auto generated Go binding around an Ethereum contract,
+// with pre-set call and transact options.
+type ERC20Session struct {
+	Contract     *ERC20            // Generic contract binding to set the session for
+	CallOpts     bind.CallOpts     // Call options to use throughout this session
+	TransactOpts bind.TransactOpts // Transaction auth options to use throughout this session
+}
+
+// ERC20CallerSession is an auto generated read-only Go binding around an Ethereum contract,
+// with pre-set call options.
+type ERC20CallerSession struct {
+	Contract *ERC20Caller  // Generic contract caller binding to set the session for
+	CallOpts bind.CallOpts // Call options to use throughout this session
+}
+
+// ERC20TransactorSession is an auto generated write-only Go binding around an Ethereum contract,
+// with pre-set transact options.
+type ERC20TransactorSession struct {
+	Contract     *ERC20Transactor  // Generic contract transactor binding to set the session for
+	TransactOpts bind.TransactOpts // Transaction auth options to use throughout this session
+}
+
+// ERC20Raw is an auto generated low-level Go binding around an Ethereum contract.
+type ERC20Raw struct {
+	Contract *ERC20 // Generic contract binding to access the raw methods on
+}
+
+// ERC20CallerRaw is an auto generated low-level read-only Go binding around an Ethereum contract.
+type ERC20CallerRaw struct {
+	Contract *ERC20Caller // Generic read-only contract binding to access the raw methods on
+}
+
+// ERC20TransactorRaw is an auto generated low-level write-only Go binding around an Ethereum contract.
+type ERC20TransactorRaw struct {
+	Contract *ERC20Transactor // Generic write-only contract binding to access the raw methods on
+}
+
+// NewERC20 creates a new instance of ERC20, bound to a specific deployed contract.
+func NewERC20(address common.Address, backend bind.ContractBackend) (*ERC20, error) {
+	contract, err := bindERC20(address, backend, backend, backend)
+	if err != nil {
+		return nil, err
+	}
+	return &ERC20{ERC20Caller: ERC20Caller{contract: contract}, ERC20Transactor: ERC20Transactor{contract: contract}, ERC20Filterer: ERC20Filterer{contract: contract}}, nil
+}
+
+// NewERC20Caller creates a new read-only instance of ERC20, bound to a specific deployed contract.
+func NewERC20Caller(address common.Address, caller bind.ContractCaller) (*ERC20Caller, error) {
+	contract, err := bindERC20(address, caller, nil, nil)
+	if err != nil {
+		return nil, err
+	}
+	return &ERC20Caller{contract: contract}, nil
+}
+
+// NewERC20Transactor creates a new write-only instance of ERC20, bound to a specific deployed contract.
+func NewERC20Transactor(address common.Address, transactor bind.ContractTransactor) (*ERC20Transactor, error) {
+	contract, err := bindERC20(address, nil, transactor, nil)
+	if err != nil {
+		return nil, err
+	}
+	return &ERC20Transactor{contract: contract}, nil
+}
+
+// NewERC20Filterer creates a new log filterer instance of ERC20, bound to a specific deployed contract.
+func NewERC20Filterer(address common.Address, filterer bind.ContractFilterer) (*ERC20Filterer, error) {
+	contract, err := bindERC20(address, nil, nil, filterer)
+	if err != nil {
+		return nil, err
+	}
+	return &ERC20Filterer{contract: contract}, nil
+}
+
+// bindERC20 binds a generic wrapper to an already deployed contract.
+func bindERC20(address common.Address, caller bind.ContractCaller, transactor bind.ContractTransactor, filterer bind.ContractFilterer) (*bind.BoundContract, error) {
+	parsed, err := abi.JSON(strings.NewReader(ERC20ABI))
+	if err != nil {
+		return nil, err
+	}
+	return bind.NewBoundContract(address, parsed, caller, transactor, filterer), nil
+}
+
+// Call invokes the (constant) contract method with params as input values and
+// sets the output to result. The result type might be a single field for simple
+// returns, a slice of interfaces for anonymous returns and a struct for named
+// returns.
+func (_ERC20 *ERC20Raw) Call(opts *bind.CallOpts, result interface{}, method string, params ...interface{}) error {
+	return _ERC20.Contract.ERC20Caller.contract.Call(opts, result, method, params...)
+}
+
+// Transfer initiates a plain transaction to move funds to the contract, calling
+// its default method if one is available.
+func (_ERC20 *ERC20Raw) Transfer(opts *bind.TransactOpts) (*types.Transaction, error) {
+	return _ERC20.Contract.ERC20Transactor.contract.Transfer(opts)
+}
+
+// Transact invokes the (paid) contract method with params as input values.
+func (_ERC20 *ERC20Raw) Transact(opts *bind.TransactOpts, method string, params ...interface{}) (*types.Transaction, error) {
+	return _ERC20.Contract.ERC20Transactor.contract.Transact(opts, method, params...)
+}
+
+// Call invokes the (constant) contract method with params as input values and
+// sets the output to result. The result type might be a single field for simple
+// returns, a slice of interfaces for anonymous returns and a struct for named
+// returns.
+func (_ERC20 *ERC20CallerRaw) Call(opts *bind.CallOpts, result interface{}, method string, params ...interface{}) error {
+	return _ERC20.Contract.contract.Call(opts, result, method, params...)
+}
+
+// Transfer initiates a plain transaction to move funds to the contract, calling
+// its default method if one is available.
+func (_ERC20 *ERC20TransactorRaw) Transfer(opts *bind.TransactOpts) (*types.Transaction, error) {
+	return _ERC20.Contract.contract.Transfer(opts)
+}
+
+// Transact invokes the (paid) contract method with params as input values.
+func (_ERC20 *ERC20TransactorRaw) Transact(opts *bind.TransactOpts, method string, params ...interface{}) (*types.Transaction, error) {
+	return _ERC20.Contract.contract.Transact(opts, method, params...)
+}
+
+// Decimals is a free data retrieval call binding the contract method 0x313ce567.
+//
+// Solidity: function decimals() view returns(uint8)
+func (_ERC20 *ERC20Caller) Decimals(opts *bind.CallOpts) (uint8, error) {
+	var (
+		ret0 = new(uint8)
+	)
+	out := ret0
+	err := _ERC20.contract.Call(opts, out, "decimals")
+	return *ret0, err
+}
+
+// Decimals is a free data retrieval call binding the contract method 0x313ce567.
+//
+// Solidity: function decimals() view returns(uint8)
+func (_ERC20 *ERC20Session) Decimals() (uint8, error) {
+	return _ERC20.Contract.Decimals(&_ERC20.CallOpts)
+}
+
+// Decimals is a free data retrieval call binding the contract method 0x313ce567.
+//
+// Solidity: function decimals() view returns(uint8)
+func (_ERC20 *ERC20CallerSession) Decimals() (uint8, error) {
+	return _ERC20.Contract.Decimals(&_ERC20.CallOpts)
+}
+
+// Name is a free data retrieval call binding the contract method 0x06fdde03.
+//
+// Solidity: function name() view returns(string)
+func (_ERC20 *ERC20Caller) Name(opts *bind.CallOpts) (string, error) {
+	var (
+		ret0 = new(string)
+	)
+	out := ret0
+	err := _ERC20.contract.Call(opts, out, "name")
+	return *ret0, err
+}
+
+// Name is a free data retrieval call binding the contract method 0x06fdde03.
+//
+// Solidity: function name() view returns(string)
+func (_ERC20 *ERC20Session) Name() (string, error) {
+	return _ERC20.Contract.Name(&_ERC20.CallOpts)
+}
+
+// Name is a free data retrieval call binding the contract method 0x06fdde03.
+//
+// Solidity: function name() view returns(string)
+func (_ERC20 *ERC20CallerSession) Name() (string, error) {
+	return _ERC20.Contract.Name(&_ERC20.CallOpts)
+}
+
+// Symbol is a free data retrieval call binding the contract method 0x95d89b41.
+//
+// Solidity: function symbol() view returns(string)
+func (_ERC20 *ERC20Caller) Symbol(opts *bind.CallOpts) (string, error) {
+	var (
+		ret0 = new(string)
+	)
+	out := ret0
+	err := _ERC20.contract.Call(opts, out, "symbol")
+	return *ret0, err
+}
+
+// Symbol is a free data retrieval call binding the contract method 0x95d89b41.
+//
+// Solidity: function symbol() view returns(string)
+func (_ERC20 *ERC20Session) Symbol() (string, error) {
+	return _ERC20.Contract.Symbol(&_ERC20.CallOpts)
+}
+
+// Symbol is a free data retrieval call binding the contract method 0x95d89b41.
+//
+// Solidity: function symbol() view returns(string)
+func (_ERC20 *ERC20CallerSession) Symbol() (string, error) {
+	return _ERC20.Contract.Symbol(&_ERC20.CallOpts)
+}

@@ -13,9 +13,17 @@ ethCommon "github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/ethclient"
 	"github.com/hermeznetwork/hermez-node/common"
+	"github.com/hermeznetwork/hermez-node/eth/contracts/erc20"
 	"github.com/hermeznetwork/hermez-node/log"
 )
 
+// ERC20Consts are the constants defined in a particular ERC20 Token instance
+type ERC20Consts struct {
+	Name     string
+	Symbol   string
+	Decimals uint64
+}
+
 // EthereumInterface is the interface to Ethereum
 type EthereumInterface interface {
 	EthCurrentBlock() (int64, error)
@@ -23,6 +31,8 @@ // EthHeaderByNumber(context.Context, *big.Int) (*types.Header, error)
 	EthBlockByNumber(context.Context, int64) (*common.Block, error)
 	EthAddress() (*ethCommon.Address, error)
 	EthTransactionReceipt(context.Context, ethCommon.Hash) (*types.Receipt, error)
+
+	EthERC20Consts(ethCommon.Address) (*ERC20Consts, error)
 }
 
 var (
@@ -264,3 +274,30 @@ Hash:        block.Hash(),
 	}
 	return b, nil
 }
+
+// EthERC20Consts returns the constants defined for a particular ERC20 Token instance.
+func (c *EthereumClient) EthERC20Consts(tokenAddress ethCommon.Address) (*ERC20Consts, error) {
+	instance, err := erc20.NewERC20(tokenAddress, c.client)
+	if err != nil {
+		return nil, err
+	}
+	name, err := instance.Name(nil)
+	if err != nil {
+		return nil, err
+	}
+
+	symbol, err := instance.Symbol(nil)
+	if err != nil {
+		return nil, err
+	}
+
+	decimals, err := instance.Decimals(nil)
+	if err != nil {
+		return nil, err
+	}
+	return &ERC20Consts{
+		Name:     name,
+		Symbol:   symbol,
+		Decimals: uint64(decimals),
+	}, nil
+}

@@ -0,0 +1,24 @@
+package eth
+
+import (
+	"os"
+	"testing"
+
+	ethCommon "github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/ethclient"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestEthERC20(t *testing.T) {
+	address := ethCommon.HexToAddress("0x44021007485550008e0f9f1f7b506c7d970ad8ce")
+	ethClient, err := ethclient.Dial(os.Getenv("ETHCLIENT_DIAL_URL"))
+	require.Nil(t, err)
+	client := NewEthereumClient(ethClient, accountAux, ks, nil)
+
+	consts, err := client.EthERC20Consts(address)
+	require.Nil(t, err)
+	assert.Equal(t, "Golem Network Token", consts.Name)
+	assert.Equal(t, "GNT", consts.Symbol)
+	assert.Equal(t, uint64(18), consts.Decimals)
+}

@@ -176,6 +176,7 @@ BlockNum   int64
 	Time       int64
 	Hash       ethCommon.Hash
 	ParentHash ethCommon.Hash
+	Tokens     map[ethCommon.Address]eth.ERC20Consts
 	// state      ethState
 }
 
@@ -200,14 +201,15 @@ func (b *Block) Next() *Block {
 	blockNext := b.copy()
 	blockNext.Rollup.Events = eth.NewRollupEvents()
 	blockNext.Auction.Events = eth.NewAuctionEvents()
-	blockNext.Eth = &EthereumBlock{
-		BlockNum:   b.Eth.BlockNum + 1,
-		ParentHash: b.Eth.Hash,
-	}
+
+	blockNext.Eth.BlockNum = b.Eth.BlockNum + 1
+	blockNext.Eth.ParentHash = b.Eth.Hash
+
 	blockNext.Rollup.Constants = b.Rollup.Constants
 	blockNext.Auction.Constants = b.Auction.Constants
 	blockNext.Rollup.Eth = blockNext.Eth
 	blockNext.Auction.Eth = blockNext.Eth
+
 	return blockNext
 }
 
@@ -360,6 +362,7 @@ BlockNum:   blockNum,
 			Time:       timer.Time(),
 			Hash:       hasher.Next(),
 			ParentHash: ethCommon.Hash{},
+			Tokens:     make(map[ethCommon.Address]eth.ERC20Consts),
 		},
 	}
 	blockCurrent.Rollup.Eth = blockCurrent.Eth
@@ -506,6 +509,23 @@ }
 	}
 
 	return nil, nil
+}
+
+// CtlAddERC20 adds an ERC20 token to the blockchain.
+func (c *Client) CtlAddERC20(tokenAddr ethCommon.Address, constants eth.ERC20Consts) {
+	nextBlock := c.nextBlock()
+	e := nextBlock.Eth
+	e.Tokens[tokenAddr] = constants
+}
+
+// EthERC20Consts returns the constants defined for a particular ERC20 Token instance.
+func (c *Client) EthERC20Consts(tokenAddr ethCommon.Address) (*eth.ERC20Consts, error) {
+	currentBlock := c.currentBlock()
+	e := currentBlock.Eth
+	if constants, ok := e.Tokens[tokenAddr]; ok {
+		return &constants, nil
+	}
+	return nil, fmt.Errorf("tokenAddr not found")
 }
 
 // func newHeader(number *big.Int) *types.Header {

@@ -62,6 +62,19 @@ block, err = c.EthBlockByNumber(context.TODO(), 2)
 	require.Nil(t, err)
 	assert.Equal(t, int64(2), block.EthBlockNum)
 	assert.Equal(t, time.Unix(2, 0), block.Timestamp)
+
+	// Add a token
+	tokenAddr := ethCommon.HexToAddress("0x44021007485550008e0f9f1f7b506c7d970ad8ce")
+	constants := eth.ERC20Consts{
+		Name:     "FooBar",
+		Symbol:   "FOO",
+		Decimals: 4,
+	}
+	c.CtlAddERC20(tokenAddr, constants)
+	c.CtlMineBlock()
+	tokenConstants, err := c.EthERC20Consts(tokenAddr)
+	require.Nil(t, err)
+	assert.Equal(t, constants, *tokenConstants)
 }
 
 func TestClientAuction(t *testing.T) {