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tip title author created status type category
1
transaction gas fee can be paid by third accout
2019-01-11
Draft
Standards Track
Core

Abstract

This draft TIP describes the mechanism of gas paying agent, when sending a transaction, others can pay the transaction fee instead of sender.

Motivation

The customers can send transactions without enough TRUE, this is friendly to DApp development.

Specification

In order for the mechanism to work, the transaction will add some messages. The original transaction takes the following form:

- AccountNonce: Number of transactions sent by the sender.
- GasPrice: Number of Wei to be paid per unit of gas for this transaction.
- GasLimit: Maximum amount of gas should be used for this transaction.
- Recipient: Address of the beneficiary for this transaction.
- Value: Amount of token to be transacted.
- Data: Virtual machine code for smart contract deployment or miscellaneous use.
- V,R,S: Cryptographic values corresponding to the signature of the transaction, and used to determine the sender of the transaction.

Here is the new form:

- AccountNonce: Number of transactions sent by the sender.
- GasPrice: Number of Wei to be paid per unit of gas for this transaction.
- GasLimit: Maximum amount of gas should be used for this transaction.
- Recipient: Address of the beneficiary for this transaction.
- Value: Amount of token to be transacted.
- Data: Virtual machine code for smart contract deployment or miscellaneous use.
- Payer: The payer sender wants the transaction to be paid by.
- V,R,S: Cryptographic values corresponding to the signature of the transaction, and used to determine the sender of the transaction.
- PV,PR,PS: Cryptographic values corresponding to the signature of the payment, used to determine the payer of the transaction.

Create

paid by sender

When a user creates a new transaction, if the transaction to be paid by himself, he can set fields Payer,PV,PR,PS nil, send the transaction to a node directly. Sign the transaction with these fields:

  • AccountNonce
  • GasPrice
  • GasLimit
  • Recipient
  • Value
  • Code This is compatible with original transaction and web3.js can work well for it.

paid by a third account

If the transaction to be paid by a third payer account:

  1. the sender signs the transaction with these fields:

    • AccountNonce
    • GasPrice
    • GasLimit
    • Recipient
    • Value
    • Code
    • Payer

  2. Then send the transaction to the payer by a offchain message.

  3. The payer signs the transaction with these fields to confirm the payment:

    • AccountNonce
    • GasPrice
    • GasLimit
    • Recipient
    • Value
    • Code
    • Sender

  4. Then sends the transaction to a node.

Validate

When a node receives a transaction, it will checks whether a transaction is valid accrording to the consensus rules:

  • validate whether the transaction is signed properly
  • if payer is setted, check the payment signature
  • ensure the nonce ordering
  • check the sender and payer's funds to cover the costs

Excute

VM excutes the transaction and deducts the transaction fee from payer account.

Implementation

  1. https://github.com/truechain/truechain-engineering-code/blob/master/core/types/transaction.go
  2. https://github.com/truechain/truechain-engineering-code/blob/master/core/types/transaction_signing.go