tip: 30
title: TRC-30 Code hash instructions
author: llwslc<llwslc@gmail.com>
discussions to: https://github.com/tronprotocol/TIPs/issues/30
category: TRC
status: Final
created: 2019-03-27
To provide a new opcode, which returns the keccak256 hash of a contract's code. Just like EIP1052 in Ethereum.
This TIP specifies a new opcode, which returns the keccak256 hash of a contract's code.
Many contracts need to perform checks on a contract's bytecode, but do not necessarily need the bytecode itself. For instance, a contract may want to check if another contract's bytecode is one of a set of permitted implementations, or it may perform analyses on code and whitelist any contract with matching bytecode if the analysis passes.
Contracts can presently do this using the EXTCODECOPY
opcode, but this is expensive, especially for large contracts, in cases where only the hash is required. As a result, we propose a new opcode, EXTCODEHASH
, which returns the keccak256 hash of a contract's bytecode.
A new opcode, EXTCODEHASH
, is introduced, with number 0x3F. The EXTCODEHASH
takes one argument from the stack, zeros the first 96 bits and pushes to the stack the keccak256 hash of the code of the account at the address being the remaining 160 bits.
In case the account does not exist 0
is pushed to the stack.
In case the account does not have code the keccak256 hash of empty data (i.e. c5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470
) is pushed to the stack.
The energy cost of the EXTCODEHASH
is 400.
As described in the motivation section, this opcode is widely useful, and saves on wasted energy in many cases.
Only the 20 last bytes of the argument are significant (the first 12 bytes are ignored) similarly to the semantics of the BALANCE
, EXTCODESIZE
and EXTCODECOPY
.
The EXTCODEHASH
distincts accounts without code and non-existing accounts.
This is consistent with the way accounts are represented in the state trie.
This also allows smart contracts to check whenever an account exists.
There are no backwards compatibility concerns.
- The
EXTCODEHASH
of the account without code isc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470
what is the keccack256 hash of empty data. - The
EXTCODEHASH
of non-existent account is0
. - The
EXTCODEHASH
of an precompiled contract is eitherc5d246...
or0
. - If
EXTCODEHASH
ofA
isX
, thenEXTCODEHASH
ofA + 2**160
isX
. - The
EXTCODEHASH
of an account that selfdestructed in the current transaction. - The
EXTCODEHASH
of an account that selfdestructed and later the selfdestruct has been reverted. - The
EXTCODEHASH
of an account created in the current transaction. - The
EXTCODEHASH
of an account that has been newly create and later the creation has been reverted. - The
EXTCODEHASH
of an account that firstly does not exist and later is empty. - The
EXTCODEHASH
of an empty account that is going to be cleared by the state clearing rule.