ERC23 token standard proposal

[Dexaran]

ERC: 223 Title: Token standard Author: Dexaran, dexaran820@gmail.com Status: Draft Type: ERC Created: 5-03.2017 Resolution: https://github.com/Dexaran/ERC23-tokens ERC20 compatible example: https://github.com/Dexaran/ERC23-tokens/blob/ERC20_compatible/ERC23_token.sol

Abstract

The following describes standard functions a token contract and contract working with specified token can implement to prevent accidentally sends of tokens to contracts and make token transactions behave like ether transactions.

Motivation

Problems of ERC20 that ERC223 will solve:

1. Impossibility of handling incoming transactions in receiver contract.
2. Tokens could be sent to contract that is not designed to work with tokens without handling and potentially could be lost. At least $72000 are lost at the moment. This problem is described here.
3. Token-transactions should match Ethereum ideology of uniformity. When a user needs to transfer his funds, he must always perform transfer. Doesn't matter is user depositing in contract or sending to an externally owned account.

Those will allow contracts to handle incoming token transactions and prevent accidentally sent tokens from being accepted by contracts. For example decentralized exchange will no more need to force users to call approve at token contract then call deposit that is calling transferFrom taking allowed tokens. Token transaction will automatically be handled inside the exchange contract.

The most important here is a call of tokenFallback when performing a transaction to a contract.

Specification

Token Contracts that work with tokens

Methods

NOTE: An important point is that contract developers must implement tokenFallback if they want their contracts to work with the specified tokens.

If the receiver does not implement the tokenFallback function, consider the contract is not designed to work with tokens, then the transaction must fail and no tokens will be transferred. An analogy with an Ether transaction that is failing when trying to send Ether to a contract that did not implement function() payable.

totalSupply

function totalSupply() constant returns (uint256 totalSupply)

Get the total token supply

name

function name() constant returns (string _name)

Get the name of token

symbol

function symbol() constant returns (string _symbol)

Get the symbol of token

decimals

function decimals() constant returns (uint8 _decimals)

Get decimals of token

balanceOf

function balanceOf(address _owner) constant returns (uint256 balance)

Get the account balance of another account with address _owner

transfer(address, uint, bytes)

function transfer(address _to, uint _value, bytes _data) returns (bool success)

function that is always called when someone wants to transfer tokens. This function must transfer tokens and invoke the function tokenFallback (address, uint256, bytes) in _to, if _to is a contract. If the tokenFallback function is not implemented in _to (receiver contract), then the transaction must fail and the transfer of tokens should not occur. If _to is an externally owned address, then the transaction must be sent without trying to execute tokenFallback in _to. _data can be attached to this token transaction and it will stay in blockchain forever (requires more gas). _data can be empty.

NOTE: The recommended way to check whether the _to is a contract or an address is to assemble the code of _to. If there is no code in _to, then this is an externally owned address, otherwise it's a contract.

IMPORTANT: Token fallback function that will be called at receiver contract must be named tokenFallback and take parametersaddress, uint256,bytes. This function must have 0xc0ee0b8a signature.

transfer(address, uint)

function transfer(address _to, uint _value) returns (bool success)

Needed due to backwards compatibility reasons because of ERC20 transfer function doesn't have bytes parameter. This function must transfer tokens and invoke the function tokenFallback(address, uint256, bytes) in _to, if _to is a contract. If the tokenFallback function is not implemented in _to (receiver contract), then the transaction must fail and the transfer of tokens should not occur.

IMPORTANT: Token fallback function that will be called at receiver contract must be named tokenFallback and take parametersaddress, uint256,bytes. This function must have 0xc0ee0b8a signature.

Events

Transfer

event Transfer(address indexed _from, address indexed _to, uint256 _value, bytes _data)

Triggered when tokens are transferred.

Contract to work with tokens

function tokenFallback(address _from, uint _value, bytes _data)

A function to handle token transfers that is called from token contract when token holder is sending tokens. _from is a token sender, _value is amount of incoming tokens and _data is attached data similar to data in Ether transactions. Works like fallback function for Ether transactions and returns nothing.

NOTE: msg.sender will be a token-contract inside the tokenFallback function. It may be important to filter which tokens are sent (by token-contract address). The token sender (the person who initiated the token transaction) will be _from inside thetokenFallback function.

IMPORTANT: This function must be named tokenFallback and take parametersaddress, uint256,bytes to match the function signature 0xc0ee0b8a.

Recommended implementation

This is highly recommended implementation of ERC 223 token: https://github.com/Dexaran/ERC23-tokens/tree/Recommended

[ghost]

This proporsal has a new mechanism to protect token tranfers to dead or incorrect contacts, but not fully compatible with original EIP20. I think we have to back compatible with EIP20 at any costs.

[Dexaran]

ERC23 token is compatible with every contract that uses ERC20 token interface. In fact the only difference in transfer is if the address-receiver is a contract then call transferToContract otherwise call basic transferToAddress that works similar to transfer in ERC20. Every contract working with ERC20 assumes you should use approval then transferFrom but not a directly transfer to contract address. approval and transferFrom is fully supported at ERC23 so there is no difference between ERC20 and ERC23 deposits handled by old contracts. The only limitation is you cant transfer ERC23 in old contract while you can transfer ERC20 and it will cause a loss of your ERC20 tokens. For example you are unable to transfer any ERC23 to dao-refund contract while you can transfer BEC in dao-refund and BEC will not be accessible any more for anyone inside dao-refund.

[ghost]

I think we have to make 'transferToContract' public and leave the old semantics of the method 'transfer'.

[Dexaran]

It will cause division of transactions to basic transfer (for addresses) and transferToContract (for contracts) as I suggested earlier. It will allow to call transfer function and send your tokens anywhere you want again. It was the main reason I decided to modify basic transfer as far as your suggestion will not add any more backward compatibility. At the other hand your suggestion to divide transferring functions assumes that UI dev will filter receiver address and decide which function to call. It means you are depending on UI dev and should trust him. I cant see any reason for doing so while there is a way to avoid it.

[Dexaran]

I decided that token transaction must contain bytes data.

It's not a solution of any of the problems I'm aiming to solve but it may be needed for future use. As long as there is a way to attach data to Ether transactions I think there should be a way to do the same with token transactions too. I don't care how exactly this will be used to attach HEX messages to token transactions or to encode inner functions execution but the way to attach data to the transaction (token or Ether) must exist.

I need more feedback to be sure what is the most important thing right now: backwards compatibility or future usability of accepted token standard.

[Dexaran]

Now ERC23 is 100% backwards compatible with ERC20 and will work with every old contract designed to work with ERC20 tokens. You can send token transaction via MEW or even using ERC20 ABI and there will be no problems with it as ERC23 is now supporting both versions of transfer(address, uint, bytes) and transfer(address, uint)

[elaineo]

I support this ECIP. I think it should be bumped for wider review.

[Dexaran]

There is a vulnurability in approve function so I'm thinking on removing it from ERC23 standard as it will never be needed any more because of tokenFallback implementation.

vulnerability is described here

I'm asking for more feedback about is approve needed and in what cases. I'm about to remove approve and transferFrom at all with break of backwards compatibility.

[splix]

@Dexaran if it's ready for Draft, let's merge it

[Dexaran]

This is ready for draft.

[realcodywburns]

lgtm

[splix]

@Dexaran could you rename it to ECIP_1021.md -> ECIP-1021.md?

[Dexaran]

Approved review required: https://github.com/Dexaran/ECIPs/pull/1

[Dexaran]

Only reviews by reviewers with write access count towards mergeability. BTW, which person decides who should have write access, and who should not?

[splix]

@Dexaran could you rename ECIP_1021.md to ECIP-1021.md before merge?

[Dexaran]

I can't. It is a protected branch and I have no write access (?). I can't change anything even in my forked branch without an "approved review".

[splix]

@Dexaran could you try again?

[Dexaran]

There is too much discussion on nonsense details. Let someone with write access merge it as-is and then rename into ECIP-1021.md. I don't see any problems here.