EIP-1014: Skinny CREATE2
Specification
Adds a new opcode (CREATE2
) at 0xf5
, which takes 4 stack arguments: endowment, memory_start, memory_length, salt. Behaves identically to CREATE
(0xf0
), except using keccak256( 0xff ++ address ++ salt ++ keccak256(init_code))[12:]
instead of the usual sender-and-nonce-hash as the address where the contract is initialized at.
The CREATE2
has the same gas
schema as CREATE
, but also an extra hashcost
of GSHA3WORD * ceil(len(init_code) / 32)
, to account for the hashing that must be performed. The hashcost
is deducted at the same time as memory-expansion gas and CreateGas
is deducted: before evaluation of the resulting address and the execution of init_code
.
0xff
is a single byte,address
is always20
bytes,salt
is always32
bytes (a stack item).
The preimage for the final hashing round is thus always exactly 85
bytes long.
The coredev-call at 2018-08-10 decided to use the formula above.
Motivation
Allows interactions to (actually or counterfactually in channels) be made with addresses that do not exist yet on-chain but can be relied on to only possibly eventually contain code that has been created by a particular piece of init code. Important for state-channel use cases that involve counterfactual interactions with contracts.
Rationale
Address formula
- Ensures that addresses created with this scheme cannot collide with addresses created using the traditional
keccak256(rlp([sender, nonce]))
formula, as0xff
can only be a starting byte for RLP for data many petabytes long. - Ensures that the hash preimage has a fixed size,
Gas cost
Since address calculation depends on hashing the init_code
, it would leave clients open to DoS attacks if executions could repeatedly cause hashing of large pieces of init_code
, since expansion of memory is paid for only once. This EIP uses the same cost-per-word as the SHA3
opcode.
Clarifications
The init_code
is the code that, when executed, produces the runtime bytecode that will be placed into the state, and which typically is used by high level languages to implement a 'constructor'.
This EIP makes collisions possible. The behaviour at collisions is specified by EIP-684:
If a contract creation is attempted, due to either a creation transaction or the
CREATE
(or futureCREATE2
) opcode, and the destination address already has either nonzero nonce, or nonempty code, then the creation throws immediately, with exactly the same behavior as would arise if the first byte in the init code were an invalid opcode. This applies retroactively starting from genesis.
Specifically, if nonce
or code
is nonzero, then the create-operation fails.
With EIP-161
Account creation transactions and the
CREATE
operation SHALL, prior to the execution of the initialisation code, increment the nonce over and above its normal starting value by one
This means that if a contract is created in a transaction, the nonce
is immediately non-zero, with the side-effect that a collision within the same transaction will always fail -- even if it's carried out from the init_code
itself.
It should also be noted that SELFDESTRUCT
(0xff
) has no immediate effect on nonce
or code
, thus a contract cannot be destroyed and recreated within one transaction.
Examples
Example 0
- address
0x0000000000000000000000000000000000000000
- salt
0x0000000000000000000000000000000000000000000000000000000000000000
- init_code
0x00
- gas (assuming no mem expansion):
32006
- result:
0x4D1A2e2bB4F88F0250f26Ffff098B0b30B26BF38
Example 1
- address
0xdeadbeef00000000000000000000000000000000
- salt
0x0000000000000000000000000000000000000000000000000000000000000000
- init_code
0x00
- gas (assuming no mem expansion):
32006
- result:
0xB928f69Bb1D91Cd65274e3c79d8986362984fDA3
Example 2
- address
0xdeadbeef00000000000000000000000000000000
- salt
0x000000000000000000000000feed000000000000000000000000000000000000
- init_code
0x00
- gas (assuming no mem expansion):
32006
- result:
0xD04116cDd17beBE565EB2422F2497E06cC1C9833
Example 3
- address
0x0000000000000000000000000000000000000000
- salt
0x0000000000000000000000000000000000000000000000000000000000000000
- init_code
0xdeadbeef
- gas (assuming no mem expansion):
32006
- result:
0x70f2b2914A2a4b783FaEFb75f459A580616Fcb5e
Example 4
- address
0x00000000000000000000000000000000deadbeef
- salt
0x00000000000000000000000000000000000000000000000000000000cafebabe
- init_code
0xdeadbeef
- gas (assuming no mem expansion):
32006
- result:
0x60f3f640a8508fC6a86d45DF051962668E1e8AC7
Example 5
- address
0x00000000000000000000000000000000deadbeef
- salt
0x00000000000000000000000000000000000000000000000000000000cafebabe
- init_code
0xdeadbeefdeadbeefdeadbeefdeadbeefdeadbeefdeadbeefdeadbeefdeadbeefdeadbeefdeadbeefdeadbeef
- gas (assuming no mem expansion):
32012
- result:
0x1d8bfDC5D46DC4f61D6b6115972536eBE6A8854C
Example 6
- address
0x0000000000000000000000000000000000000000
- salt
0x0000000000000000000000000000000000000000000000000000000000000000
- init_code
0x
- gas (assuming no mem expansion):
32000
- result:
0xE33C0C7F7df4809055C3ebA6c09CFe4BaF1BD9e0