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RSKIP125.md

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rskip title description status purpose author layer complexity created
125
Create2
Adopted
Sca, Usa
SMS (@sebastians)
Core
1
2019-04-29

Create2

RSKIP 125
Title Create2
Created 29-APR-19
Author SMS
Purpose Sca, Usa
Layer Core
Complexity 1
Status Adopted

Abstract

The purpose of this IP is to implement the CREATE2 opcode, as added to the Ethereum VM in the EIP 1014

Motivation

Enables the creation of contracts with deterministic and repeatable addresses. This functionality is required for state channels interacting with a contract that only needs to be created on arbitration (also called counterfactual channels).

Specification

Adds a new opcode at 0xf5, which takes 4 stack arguments: endowment, memory_start, memory_length, salt. Behaves identically to CREATE, 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 always 20 bytes,
  • salt is always 32 bytes (a stack item).

The preimage for the final hashing round is thus always exactly 85 bytes long.

Rationale

Address formula

  • Ensures that addresses created with this scheme cannot collide with addresses created using the traditional keccak256(rlp([sender, nonce])) formula, as 0xff 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.

The CREATE behavior change

The original EIP specified what to do in cases of a hash collision of the new address. Basically, in order to prevent this problem, each new contract created by these opcodes would start with its nonce in one, instead of zero. In addition, when there is a collision there is a check done if the existing contract has either non empty code, or non zero nonce, if one of this checks is true then the contract creation fails as if the init_code program would fail.

This RSKIP introduces a new behavior for the CREATE opcode, because every contract created will start with nonce 1, and fail in the rare case that a contract with the same address was previously created. The behavior is exactly the same than in the Ethereum VM, thus improving compatibility.

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

Copyright

Copyright and related rights waived via CC0.