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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
The following values are (non-configurable) constants used throughout the specification.
| Name | Value |
|---|---|
DEPOSIT_CONTRACT_TREE_DEPTH |
2**5 (= 32) |
Configuration
Note: The default mainnet configuration values are included here for spec-design purposes.
The different configurations for mainnet, testnets, and YAML-based testing can be found in the configs/constant_presets directory.
These configurations are updated for releases and may be out of sync during dev changes.
| Name | Value |
|---|---|
DEPOSIT_CHAIN_ID |
1 |
DEPOSIT_NETWORK_ID |
1 |
DEPOSIT_CONTRACT_ADDRESS |
TBD |
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 the Ethereum 1.0 chain defined by the chain-id -- DEPOSIT_CHAIN_ID -- and the network-id -- DEPOSIT_NETWORK_ID -- for deposits of ETH to the beacon chain. Validator balances will be withdrawable to the shards in Phase 2.
Note: See here for a comprehensive list of public Ethereum chain chain-id's and network-id's.
deposit function
The deposit contract has a public deposit function to make deposits. It takes as arguments bytes calldata pubkey, bytes calldata withdrawal_credentials, bytes calldata signature, bytes32 deposit_data_root. The first three arguments populate a DepositData object, and deposit_data_root is the expected DepositData root as a protection against malformatted calldata.
Deposit amount
The amount of ETH (rounded down to the closest Gwei) sent to the deposit contract is the deposit amount, which must be of size at least MIN_DEPOSIT_AMOUNT Gwei. Note that ETH consumed by the deposit contract is no longer usable on Ethereum 1.0.
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_PREFIXwithdrawal_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.
DepositEvent log
Every Ethereum 1.0 deposit emits a DepositEvent 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.
Solidity code
The deposit contract source code, written in Solidity, 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.