# Pureth [EIP-7919](https://github.com/ethereum/EIPs/blob/master/EIPS/eip-7919.md) Implementation for Nimbus-EL
## Motivation
Ethereum users today rely heavily on trusted JSON-RPC endpoints and third-party indexers for accessing and verifying blockchain data. This centralized model introduces critical issues:
- users can be misled by incorrect or incomplete data if a provider is compromised
- wallets and applications risk privacy loss through request profiling
- developers face increasing infrastructure costs
The Pureth Meta-EIP (EIP-7919) addresses these systemic shortcomings by transitioning core execution-layer structures—blocks, transactions, and receipts—to a verifiable SSZ-based format. This enables correctness and completeness proofs over standard RPC responses, allowing any light client, dApp, or third-party tool to trustlessly verify the data they consume.
These changes lay the foundation for a trust-minimized, privacy-preserving, and cost-efficient data access infrastructure for Ethereum.
### LOG Reform for Pureth
Log Reform is really importance part of Pureth which addresses major inefficiencies in current Logs.
Working on LOG Reform would solve following shortcomings :
- Smart contract wallets have to fetch and verify additional transaction receipts within a queried block range because Bloom filters produce false positives, leading to inefficient log retrieval.
- Fetching full receipts because of false positives is impractical for Light clients and mobile devices with resource constraints.
- Eth transfers from smart contracts don't emit logs which leads to problems in tracking transfers.
#### Why important ?
Working on Log Reform is important for following reasons
- Recent implementation from `Geth` has shown that new log indexer returns the results for `eth_getLogs` in milliseconds which other clients with BloomFilter might take few seconds.
- It will help lightClient and dapps to be more efficient by reducing the unnecessary data fetching.
- Reduce data overhead with compact `SSZ` encoding, enable trusless log retrieval with `Merkle proofs`.
- SSZ encoded logs will be available for all Eth Transfers(e.g., CALL, SELFDESTRUCT) and will be good for tracing.
### Normalized transactions / receipts + Serialization harmonization
Ethereum’s execution layer today relies on RLP/MPT-based data structures and JSON-RPC endpoints that together introduce friction, inefficiency, and trust assumptions at multiple levels:
- Core RPC fields (e.g. from, contractAddress, per-tx gasUsed, logIndex, and the “standard” txHash) are not committed on-chain in a directly accessible form
- RLP encoding and linear Merkle-Patricia Tries force clients to fetch and hash entire blobs (full transaction, full receipt, or whole trie branches) even when they only need to verify a single field or a single log.
- withdrawals are stored in SSZ on the Consensus layer but still hashed via an MPT in the Execution layer, creating duplicate codepaths and two different proof formats for the exact same data.
- most client-to-client and client-to-dApp communication remains JSON over HTTP, which is verbose to encode/decode, difficult to prove, and prevents clients from independently recomputing block hashes or verifying payloads without syncing whole blobs.
## Project description
This project will implement EIP-7919 (Pureth) – and its constituent EIPs – in the Nimbus Execution Layer (Nimbus-EL) client.
Each sub-section below outlines what the proposal aims to achieve for the respective EIP:
### EIP-7745:Two dimensional log filter data structure
We will start the work by focussing on the implemention of [EIP-7745:Two dimensional log filter data structure](https://github.com/ethereum/EIPs/blob/master/EIPS/eip-7745.md) in Nimbus EL :-
- Implement a two-dimensional SSZ index (by block and transaction) for precise, efficient log retrieval.
- Provide SSZ-encoded logs with Merkle proofs, verifiable against block headers.
- Remove the need for Bloom filters.
- Updated eth_getLogs with proofs
Once the work on EIP-7745 is complete, we will prioritize other log reform EIPs.
1. EIP-7708: ETH Transfers Emit a Log
The purpose of this EIP is to make all Eth transfers emit logs because currently smart contracts don't emit logs for Eth transfers and this leads to problem in tracking the transfers sometimes.
2. EIP-7799: System Logs
Some Eth balance changes are missing even with after the implementation of EIP-7708, So this EIP aims to add a new list to add all Block level logs so that `eth_getLogs` will be able to provide all the history.
### EIP-6404: SSZ transactions and EIP-6466: SSZ receipts
On the parallel front we will start with the [EIP-6404: SSZ Transactions](https://eips.ethereum.org/EIPS/eip-6404) and followed by [EIP-6466: SSZ receipts](https://eips.ethereum.org/EIPS/eip-6466) in Nimbus El.
#### SSZ transactions
- Define the SSZ Transaction container (including all legacy and new fields) using the ProgressiveContainer.
- Migrate Nimbus’s transaction serialization and deserialization from RLP to SSZ.
- Replace the MPT-based transactions_root in the block header with an SSZ Merkle‐tree root over the SSZ‐encoded transaction list.
- Preserve backward compatibility: accept legacy RLP transactions (converting them into SSZ internally).
- Update the Engine API (executePayload, getPayload, etc.) to consume and produce SSZ‐encoded transactions.
#### SSZ receipts
- Define the SSZ Receipt container(s)—BasicReceipt, CreateReceipt, SetCodeReceipt—with explicit from_, gas_used, contract_address, logs, status, and optional authorities.
- Migrate Nimbus’s receipt generation to produce SSZ receipts instead of RLP tuples.
- Compute the block header’s receipts_root as the SSZ Merkle‐tree root over the SSZ receipt list.
- Remove the legacy logsBloom field (via EIP-7668) from headers and receipts.
- Ensure eth_getTransactionReceipt and related JSON-RPC methods return consistent data while sourcing from the new SSZ receipts.
The following will also be worked upo if there a good enough timeline remaining:
EIP-6465: SSZ withdrawals root
EIP-7807: SSZ execution blocks (End goal of Tamaghna Stretch)
## Specification
For each EIP, this section will eventually detail the technical implementation plan. Here we include placeholders for what those details should cover: architecture changes, algorithms, data structures, and any relevant interfaces or API updates
### EIP-7745:Two dimensional log filter data structure
Implementing EIP-7745 in [Nimbus-EL](https://github.com/status-im/nimbus-eth1) involves updating the RPC layer to build and query the SSZ log filter, generate Merkle proofs, and handle pattern matching.
1. Define LogEntry and LogFilter structs
```nim
type LogEntry = object
address: Address
topics: List[Bytes32, 4]
data: Bytes
blockNumber: uint64
txHash: Bytes32
logIndex: uint64
type LogFilter = ProgressiveList[LogEntry]
```
- Use `ProgressiveList` for dynamic log growth
2. Build Two-Dimensional Log Index
The log index is constructed during receipt processing to enable efficient log retrieval. Each log entry is stored with its associated metadata, and logs are organized in a two-dimensional structure (by block and transaction). Additionally, Logs are stored in per-block Merkle trees, with roots linked to the block’s state or receipt trie for verifiable queries.
```nim
proc buildLogIndex(receipts: seq[Receipt], block: Block): LogFilter =
for receipt in receipts:
for log in receipt.logs:
result.add(LogEntry(
address: log.address,
topics: log.topics,
data: log.data,
blockNumber: block.number,
txHash: receipt.txHash,
logIndex: log.index
))
# Add a dummy log entry to mark the end of the block's logs
result.add(LogEntry(
address: Address(zeros(20)),
topics: @[],
data: @[],
blockNumber: block.number,
txHash: Bytes32(zeros(32)),
logIndex: high(uint64)
))
```
3. Implement FNV-1a Hashing for Filtering
4. Pattern Matching and Verification
- Implement `singleProver`, `matchAnyProver`, and `matchSequenceProver` (inspired by Geth PoC)
- Use set operations for union (matchAnyProver) and intersection (matchSequenceProver)
5. Process Partial Proofs
- Handle unproven gaps in filter rows
- Treat unproven gaps as potential match ranges, ensuring exhaustiveness. Verify count field for partial proofs.
6. Update `eth_getLogs`
- Modify to return SSZ-encoded LogFilter with proofs
7. Test with Provided Vectors
- Implement binary proof parsing (little-endian) and validate against JSON test cases. Integrate with Nimbus’s test suite (tests directory).
8. Test with Kurtosis (Local testnet)
- Send transactions (e.g., ERC-20, EIP-7708 logs), verify SSZ logs and proofs
### EIP-6404: SSZ Transactions
1. Define the SSZ Transaction container
```
type Transaction* = CompatibleUnion[
RlpTransaction
]
type RlpTransaction* = CompatibleUnion[
RlpLegacyReplayableBasicTransaction,
RlpLegacyReplayableCreateTransaction,
RlpLegacyBasicTransaction,
RlpLegacyCreateTransaction,
RlpAccessListBasicTransaction,
RlpAccessListCreateTransaction,
RlpBasicTransaction,
RlpCreateTransaction,
RlpBlobTransaction,
RlpSetCodeTransaction
]
```
2. Serialization & Deserialization
- Replace all RLP-based encodeTransaction and decodeTransaction calls with SSZ serializers.
- Implement lossless conversion from legacy RLP transactions to SSZ (fromRLP(txRlp): SSZTransaction).
3. Block Header Changes
In the block builder, compute
```
nim
blockHeader.transactions_root = SSZHashTreeRoot(txList: seq[SSZTransaction])
```
instead of the MPT root.
4. Engine API Updates
- Update engine_getPayload / engine_executePayload handlers to accept/return SSZ‐encoded transactions in the ExecutionPayload.
- Maintain backward compatibility by detecting the fork epoch and routing legacy clients through an RLP codepath.
5. Testing
- Unit tests for SSZ Transaction round-trip encoding/decoding.
- Consensus tests: verify that the SSZ transactions_root matches reference vectors.
- Mempool & devp2p: ensure SSZ txs are hashed and propagated correctly.
### EIP-6466: SSZ Receipts
1. Define the SSZ Receipt union and container types
```
type Receipt* = CompatibleUnion[
BasicReceipt,
CreateReceipt,
SetCodeReceipt
]
## Receipt for regular transactions (no contract create)
type BasicReceipt* = ProgressiveContainer[active_fields=[1,1,0,1,1]](
from_: ExecutionAddress, # signer address
gas_used: GasAmount, # exact gas used
logs: ProgressiveList[Log],
status: bool # success/failure
)
## Receipt for contract-creation transactions
type CreateReceipt* = ProgressiveContainer[active_fields=[1,1,1,1,1]](
from_: ExecutionAddress,
gas_used: GasAmount,
contract_address: ExecutionAddress,
logs: ProgressiveList[Log],
status: bool
)
## Receipt for SetCode (EIP-7702) transactions
type SetCodeReceipt* = ProgressiveContainer[active_fields=[1,1,0,1,1,1]](
from_: ExecutionAddress,
gas_used: GasAmount,
logs: ProgressiveList[Log],
status: bool,
authorities: ProgressiveList[ExecutionAddress]
)
```
- Wraps every historical RLP-based transaction type in one SSZ union.
- Retains the original RLP payload and TransactionType tag in the SSZ bytes, enabling perfect round-trip back to RLP and preserving legacy sig_hash and txHash.
- Allows SSZ serializers to treat all transactions uniformly while still encoding the original RLP shape when requested.
2. Receipt Generation
After each transaction execution, collect:
- from_ (sender address, from signature recovery)
- gas_used (measure per‐tx gas rather than cumulative)
- logs (as SSZ Log objects, preserving address/topics/data)
- contract_address if it was a CREATE tx
- authorities for SetCode txs
Instantiate the appropriate SSZ container and append to the block’s receipt list.
3. Block Header Changes
- Replace the MPT receipts root with an SSZ hash tree root:
```
blockHeader.receipts_root = SSZHashTreeRoot(receiptList: seq[Receipt])
```
- Remove the legacy logsBloom field from both headers and receipts.
4. JSON-RPC & Engine API Updates
5. Backwards Compatibility
- For blocks prior to the SSZ‐receipts fork, continue serving RLP receipts and computing the MPT root.
- After fork activation, Nimbus switches to SSZ receipts automatically.
6. Testing & Validation
Unit Tests:
- Round-trip SSZ encode/decode for each receipt variant.
- Verify that from_, gas_used, contract_address, and authorities match expected values.
Consensus Vectors:
- Compare receipts_root against reference SSZ roots for sample blocks.
Integration Tests:
Run a private devnet with the SSZ receipts+Transactions fork block; ensure eth_getTransactionReceipt returns correct data and legacy clients remain compatible.
Performance Benchmarks:
Measure RPC latency and storage impact before vs. after using SSZ.
### EIP-6465: SSZ Withdrawals Root
Aligning withdrawals with SSZ removes MPT complexity and unifies proof formats.
1. SSZ Withdrawals List
```
Withdrawal(ProgressiveContainer[active_fields=[1, 1, 1, 1]]):
index: WithdrawalIndex
validator_index: ValidatorIndex
address: ExecutionAddress
amount: Gwei
```
2. Block Header & Payload Changes
4. Codepath Cleanup
- Remove MPT‐related withdrawal hashing and merkle proof code.
- Ensure CL‐EL test compatibility: Nimbus-CL proofs of withdrawals now match Nimbus-EL’s SSZ root.
4. Unit tests for SSZ Withdrawals list.
- Cross‐client sync test: process a block in Nimbus-EL and verify withdrawals_root in Nimbus-CL.
### EIP-7807: SSZ Execution Blocks
1. Define the SSZ ExecutionBlockHeader
```
class ExecutionBlockHeader(
ProgressiveContainer[active_fields=[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1]]):
parent_hash: Root
miner: ExecutionAddress
state_root: Bytes32
transactions_root: Root # EIP-6404 transactions.hash_tree_root()
receipts_root: Root # EIP-6466 receipts.hash_tree_root()
number: uint64
gas_limits: GasAmounts
gas_used: GasAmounts
timestamp: uint64
extra_data: ByteList[MAX_EXTRA_DATA_BYTES]
mix_hash: Bytes32
base_fees_per_gas: BlobFeesPerGas
withdrawals_root: Root # EIP-6465 withdrawals.hash_tree_root()
excess_gas: GasAmounts
parent_beacon_block_root: Root
requests_hash: Bytes32 # EIP-6110 execution_requests.hash_tree_root()
system_logs_root: Root # EIP-7799 system_logs.hash_tree_root()
```
2. Block Import/Export
- Migrate Nimbus-EL’s block serialization to SSZ for both headers and full payloads.
- Remove encodings in engine_getPayload / engine_executePayload and transition to ssz
- Update consensus‐to‐execution and execution‐to‐consensus flows to use SSZ objects directly.
3. Testing & Benchmarking
- End-to-end tests: import/export SSZ blocks, verify block hashes in CL.
- Performance benchmarks: measure payload serialization/deserialization speed and binary API throughput(maybe for binary api).
### STEEL Effort
These ssz changes need a stable static testing suite to be tested against and validated upon,Hence there will also be a set of tests developed to test these impl upon initially for the part that consistutes the SSZ changes and lated for the logs parts of the EIP.
## Roadmap
The roadmap and implemention timeline can be broken as follows:-
The following is the timeline by Vineet:
#### Phase 1: 2 weeks
- Finalize the technical implementation details.
- Nimbus-EL architechture understanding.
- Basic Understanding of Nim language
#### Phase2: 7-8 weeks
- EIP-7745: Two-Dimensional Log Filter Data Structure.
- Replace bloom filter with 2D log index
- Test new logs against JSON RPCs
- Test with Kurtosis
#### Phase3: 6-7 weeks
- For other Log reform EIPs
- EIP-7708: ETH Transfers Emit a Log
- Effort estimate
- Should take 5 weeks (approx) to implement
- Emit SSZ logs for opcodes like SELFDESTRUCT or CALL transfers.
- Simulate tests for Eth transfer in smart contract wallet
- EIP-7799: System Logs
- Effort estimate
- Shold take same effort as EIP-7708
The following is by Tamaghna :
#### Phase 1: 5 weeks
- start Implementation of the EIP 6404
- start Implementation of the EIP 6466
- implement the necessary tests realted to 6404 and 6466 in eels
### Phase 2 : 2 weeks
- start Implementation of the EIP 6465
- start Implementation of the EIP 7807
- implement the eels equivalent of the eips
### Phase 3: 5 weeks
- Testing against hive with eels
- set up a local devnet for ssz testing
- integrate with Vineet on the log parts and complete test coverage and interop for a working pureth devnet by devcon -?
#### Possible challenges
- Learning Nim and Nimbus Architecture
- Building a two-dimensional SSZ-based log index (ProgressiveList, EIP-7916) with block and transaction dimensions.
- Validating the implementation against test vectors (proof_test_vectors) and ensuring compatibility with Kurtosis testnet queries is time-consuming.
#### Goal of the project
- Trustless Log Retrieval
- Support decentralization goals of Ethereum by reduding reliance on trusted JSON RPC providers.
- Providing ssz encoded logs with Merkle proofs will enable light clients, dapps and smart contract wallets to verify correcness of logs against block headers.
- Eliminate Bloom Filter Inefficiencies
- Replace bloom filter with 2D log Log index will reduce unnecessary data fetching due to false positives nature of bloom filters
- Improve scalability and efficiency of log queries `eth_getLogs`
## Collaborators
Vineet and @samyxandy (Tamaghna)
- Vineet :- Focussing on Log Reform EIP-7745: Two dimensional log filter data structure
- Tamaghana :- Focussing on EIP-6404: SSZ transactions
We will coordinate and work parallely on separate EIPs for implementation, once core EIPs (7745 and 6404) are done , we will work on other EIPs for Log Reform and Remove old tx types categories in Pureth.
## Mentors
Etan is the mentor for Pureth EIP-7919 implementation
## Resources
| Resource | link |
| --------------------------------------- | ---------------------------------------------------------------------- |
| Pureth EIP-7919 | https://github.com/ethereum/EIPs/blob/master/EIPS/eip-7919.md |
| EIP-7745 : 2D log filter data structure | https://github.com/ethereum/EIPs/blob/master/EIPS/eip-7745.md |
| EIP-7745 details by Zsolt | https://github.com/zsfelfoldi/eip-7745/blob/main/proof_verification.md |
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