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Ethereum 2.0 Phase 0 -- Deposit Contract
Notice: This document is a work-in-progress for researchers and implementers.
Table of contents
Introduction
This document represents the specification for the beacon chain deposit contract, part of Ethereum 2.0 Phase 0.
Constants
Contract
| Name | Value |
|---|---|
DEPOSIT_CONTRACT_ADDRESS |
TBD |
DEPOSIT_CONTRACT_TREE_DEPTH |
2**5 (= 32) |
Ethereum 1.0 deposit contract
The initial deployment phases of Ethereum 2.0 are implemented without consensus changes to Ethereum 1.0. A deposit contract at address DEPOSIT_CONTRACT_ADDRESS is added to Ethereum 1.0 for deposits of ETH to the beacon chain. Validator balances will be withdrawable to the shards in Phase 2 (i.e. when the EVM 2.0 is deployed and the shards have state).
deposit function
The deposit contract has a public deposit function to make deposits. It takes as arguments pubkey: bytes[48], withdrawal_credentials: bytes[32], signature: bytes[96] corresponding to a DepositData object.
Deposit amount
The ETH sent to the deposit contract, i.e. the deposit amount, is burnt on Ethereum 1.0. The minimum deposit amount is MIN_DEPOSIT_AMOUNT Gwei.
Withdrawal credentials
One of the DepositData fields is withdrawal_credentials. It is a commitment to credentials for withdrawing validator balance (e.g. to another validator, or to shards). The first byte of withdrawal_credentials is a version number. As of now, the only expected format is as follows:
withdrawal_credentials[:1] == BLS_WITHDRAWAL_PREFIX_BYTEwithdrawal_credentials[1:] == hash(withdrawal_pubkey)[1:]wherewithdrawal_pubkeyis a BLS pubkey
The private key corresponding to withdrawal_pubkey will be required to initiate a withdrawal. It can be stored separately until a withdrawal is required, e.g. in cold storage.
Deposit log
Every Ethereum 1.0 deposit emits a Deposit log for consumption by the beacon chain. The deposit contract does little validation, pushing most of the validator onboarding logic to the beacon chain. In particular, the proof of possession (a BLS12-381 signature) is not verified by the deposit contract.
Vyper code
The deposit contract source code, written in Vyper, is available here.
Note: To save on gas the deposit contract uses a progressive Merkle root calculation algorithm that requires only O(log(n)) storage. See here for a Python implementation, and here for a formal correctness proof.