Appends validator deposits to the Execution Layer block structure. This shifts responsibility of deposit inclusion and validation to the Execution Layer and removes the need for deposit (or eth1data) voting from the Consensus Layer.
Validator deposits list supplied in a block is obtained by parsing deposit contract log events emitted by each deposit transaction included in a given block.
Validator deposits are a core component of the proof-of-stake consensus mechanism. This EIP allows for an in-protocol mechanism of deposit processing on the Consensus Layer and eliminates the proposer voting mechanism utilized currently. This proposed mechanism relaxes safety assumptions and reduces complexity of client software design, contributing to the security of the deposits flow. It also improves validator UX.
Advantages of in-protocol deposit processing consist of, but are not limited to, the following:
| Name | Value | Comment |
|---|---|---|
DEPOSIT_REQUEST_TYPE | b'0' | The EIP-7685 request type byte for deposit operation |
| Name | Value | Comment |
|---|---|---|
DEPOSIT_CONTRACT_ADDRESS | 0x00000000219ab540356cbb839cbe05303d7705fa | Mainnet |
DEPOSIT_EVENT_SIGNATURE_HASH | 0x649bbc62d0e31342afea4e5cd82d4049e7e1ee912fc0889aa790803be39038c5 |
DEPOSIT_CONTRACT_ADDRESS, DEPOSIT_EVENT_SIGNATURE_HASH parameters MUST be included into client software binary distribution.
FORK_BLOCK -- the first block in a blockchain after this EIP has been activated.The structure denoting the new deposit request consists of the following fields:
pubkey: Bytes48withdrawal_credentials: Bytes32amount: uint64signature: Bytes96index: uint64Deposits are a type of EIP-7685 request, with the following encoding:
Beginning with the FORK_BLOCK, each deposit accumulated in the block MUST appear in the EIP-7685 requests list
in the order they appear in the logs. To illustrate:
Consensus layer changes can be summarized into the following list:
ExecutionRequests is extended with a new deposit_requests field to accommodate deposit requests list.BeaconState is appended with deposit_requests_start_index used to switch from the former deposit mechanism to the new one.Eth1Data poll.process_deposit_request function is added to the block processing routine to handle deposit_requests processing.Eth1Data poll once transition is completed.Detailed consensus layer specification can be found in following documents:
electra/beacon-chain.md -- state transition.electra/validator.md -- validator guide.electra/fork.md -- EIP activation.Due to the large follow distance of Eth1Data poll an index of a new validator assigned during deposit processing remains the same across different branches of a block tree, i.e. with existing mechanism (pubkey, index) cache utilized by consensus layer clients is re-org resilient. The new deposit machinery breaks this invariant and consensus layer clients will have to deal with a fact that a validator index becomes fork dependent, i.e. a validator with the same pubkey can have different indexes in different block tree branches.
Detailed analysis shows that process_deposit function is the only place requiring a fork dependent (pubkey, index) cache.
Eth1Data poll deprecationConsensus layer clients will be able to remove Eth1Data poll mechanism in an uncoordinated fashion once transition period is finished. The transition period is considered as finished when a network reaches the point where state.eth1_deposit_index == state.deposit_requests_start_index.
index fieldDeposit index is used to deterministically initialize deposit_requests_start_index in the BeaconState, this prevents same deposit from being applied twice during Eth1Data poll deprecation.
The list is unbounded because of negligible data complexity and absence of potential DoS vectors. See Security Considerations for more details.
DEPOSIT_CONTRACT_ADDRESS and DEPOSIT_EVENT_SIGNATURE_HASHDepending on the design, Deposit smart contract can emit different type of events when deposit is being processed. For instance, Deposit smart contract on Sepolia emits Transfer in addition to DepositEvent. Thus it is important to filter out irrelevant events.
This EIP introduces backwards incompatible changes to the block structure and block validation rule set. But neither of these changes break anything related to user activity and experience.
At the time of the latest update of this document, the total number of submitted deposits is 1,899,120 which is 348MB of deposit data. Assuming frequency of deposit transactions remains the same, historic chain data complexity induced by this EIP can be estimated as 84MB per year which is negligible in comparison to other historical data.
After the beacon chain launch in December 2020, the biggest observed spike in a number of submitted deposits was on June 1, 2023. More than 12,000 deposit transactions were submitted during 24 hours which on average is less than 2 deposit, or 384 bytes of data, per block.
Considering the above, we conclude that data complexity introduced by this proposal is negligible.
The code in the deposit contract costs 15,650 gas to run in the cheapest case (when all storage slots are hot and only a single leaf has to be modified). Some deposits in a batch deposit are more expensive, but those costs, when amortized over a large number of deposits, are small at around ~1,000 gas per deposit. Under current gas pricing rules an extra 6,900 gas is charged to make a CALL that transfers ETH, this is a case of inefficient gas pricing and may be reduced in the future. For future robustness the beacon chain needs to be able to withstand 1,916 deposits in a 30M gas block (15,650 gas per deposit). The limit under current rules is less than 1,271 deposits in a 30M gas block.
With 1 ETH as a minimum deposit amount, the lowest cost of a byte of deposit data is 1 ETH/192 ~ 5,208,333 Gwei. This is several orders of magnitude higher than the cost of a byte of transaction's calldata, thus adding deposit operations to a block does not increase DoS attack surface of the execution layer.
The most consuming computation of deposit processing is signature verification. Its complexity is bounded by a maximum number of deposits per block which is around 1,271 with 30M gas block at the moment. So, it is ~1,271 signature verifications which is roughly ~1.2 seconds of processing (without optimisations like batched signatures verification). An attacker would need to spend 1,000 ETH to slow down block processing by a second which isn't sustainable and viable attack long term.
An optimistically syncing node may be susceptible to a more severe attack scenario. Such a node can't validate a list of deposits provided in a payload which makes it possible for attacker to include as many deposits as the limitation allows to. Currently, it is 8,192 deposits (1.5MB of data) with rough processing time of 8s. Considering an attacker would need to sign off on this block with its crypto economically viable signature (which requires building an alternative chain and feeding it to a syncing node), this attack vector is not considered as viable as it can't result in a significant slow down of a sync process.
An optimistically syncing node has to rely on the honest majority assumption. That is, if adversary is powerful enough to finalize a deposit sequence, a syncing node will have to apply these deposits disregarding the validity of deposit requests with respect to the execution of a given block. Thus, an adversary that can finalize an invalid chain can also convince an honest node to accept fake deposits. The same is applicable to the validity of execution layer world state today and a new deposit processing design is within boundaries of the existing security model in that regard.
Online nodes can't be tricked into this situation because their execution layer validates supplied deposits with respect to the block execution.
This EIP removes a hard limit on a number of deposits per epoch and makes a block gas limit the only limitation on this number. That is, the limit on deposits per epoch shifts from MAX_DEPOSITS * SLOTS_PER_EPOCH = 512 to max_deposits_per_30m_gas_block * SLOTS_PER_EPOCH ~ 32,768 at 30M gas block (we consider max_deposits_per_30m_gas_block = 1,024 for simplicity).
This change affects a number of top ups per epoch which is one of the inputs to the weak subjectivity period computation. One can top up own validators to instantly increase a portion of stake it owns with respect to those validators that are leaking. The analysis does not demonstrate significant reduction of a weak subjectivity period sizes. Moreover, such an attack is not considered as viable because it requires a decent portion of stake to be burned as one of preliminaries.
Copyright and related rights waived via CC0.