In Altair, light client sync protocol exchanges `BeaconBlockHeader`
structures for tracking current progress. Wrapping `BeaconBlockHeader`
inside a `LightClientHeader` allows future extensions of this header,
e.g., to also track `ExecutionPayloadHeader`.
Note: This changes the JSON REST format by adding a `beacon` nesting.
For SSZ, the serialization format stays same (but overall root changes).
* Add @description decorator
* Unify test case naming style
* more clean ups
* Altair tests cleanup
* Clean up Altair and Bellatrix `process_deposit` tests
* Clean up Bellatrix tests
* Clean up Capella tests
* PR feedback from @ralexstokes
* Add comments on the deposit fork version tests
* Remove `test_incorrect_sig_other_version` since it is duplicate to `test_ineffective_deposit_with_bad_fork_version`
* Add `test_ineffective_deposit_with_current_fork_version`
While the light client sync protocol currently provides access to the
latest `BeaconBlockHeader`, obtaining the matching execution data needs
workarounds such as downloading the full block.
Having ready access to the EL state root simplifies use cases that need
a way to cross-check `eth_getProof` responses against LC data.
Access to `block_hash` unlocks scenarios where a CL light client drives
an EL without `engine_newPayload`. As of Altair, only the CL beacon
block root is available, but the EL block hash is needed for engine API.
Other fields in the `ExecutionPayloadHeader` such as `logs_bloom` may
allow light client applications to monitor blocks for local interest,
e.g. for transfers affecting a certain wallet. This enables to download
only the few relevant blocks instead of every single one.
A new `LightClientStore` is proposed into the Capella spec that may be
used to sync LC data that includes execution data. Existing pre-Capella
LC data will remain as is, but can be locally upgraded before feeding it
into the new `LightClientStore` so that light clients do not need to run
a potentially expensive fork transition at a specific time. This enables
the `LightClientStore` to be upgraded at a use case dependent timing at
any time before Capella hits. Smart contract and embedded deployments
benefit from reduced code size and do not need synchronization with the
beacon chain clock to perform the Capella fork.
Introduce `get_lc_beacon_slot` and `get_lc_beacon_root` accessors
similar to `get_current_slot(state)` to account for future extensions
to the light client header structure that may override how those fields
are accessed. Idea is to extend with execution accessors in the future.
Introduce `block_to_light_client_header` helper function to enable
future forks to override it with additional info (e.g., execution),
without having to change the general light client logic.
Likewise, update existing light client data creation flow to use
`block_to_light_client_header` and default-initialize empty fields.
Furthermore, generalize `create_update` helper to streamline test code
using `block_to_light_client_header`.
Note: In Altair spec, LC header is the same as `BeaconBlockHeader`.
however; future forks will extend it with more information.
* EIP4844: bytes_to_bls_field() must not accept values >= BLS_MODULUS
bytes_to_bls_field() will be used in the precompile and hence it should error out when provided with malicious inputs.
* EIP4844: Add hash_to_bls_field() for use in compute_challenges()
The previous commit made bytes_to_bls_field() be strict about its inputs. However in compute_challenges() we are
dealing with Fiat-Shamir and hash outputs that could be innocuously higher than the modulus. For this reason we add the
hash_to_bls_field() helper for use in compute_challenges().
* EIP4844: Further use of bytes_to_bls_field() // Fix executable spec
Co-authored-by: Hsiao-Wei Wang <hsiaowei.eth@gmail.com>
Additionally, it makes the Fiat-Shamir hashing logic more robust by making the challenges independent of each other. It also makes it more efficient to implement by moving both challenge computations to a single function needing a single transcript hash.
Co-authored-by: George Kadianakis <desnacked@riseup.net>
Co-authored-by: Dankrad Feist <mail@dankradfeist.de>
- Implemented many of Alex's comments including reinsertion of the
withdrawal index in the BeaconState
- Implemented Sean's suggestion of separating the logic for block
production so that one matches the list in the payload with what
`get_expected_withdrawals` returns
- Changed `get_expected_wihdrawals` to match the current behavior and
moved it to `beacon-chain.md`
This commit changes the public API of the KZG library to the following high-level API:
```
- verify_kzg_proof()
- compute_aggregate_kzg_proof()
- verify_aggregate_kzg_proof()
- blob_to_kzg_commitment()
```
compared to the previous much more low-level API:
```
- compute_powers()
- matrix_lincomb()
- lincomb()
- bytes_to_bls_field()
- evaluate_polynomial_in_evaluation_form()
- verify_kzg_proof()
- compute_kzg_proof()
```
This means that all the cryptographic logic (including Fiat-Shamir) is now isolated and hidden in the KZG library and the `validator.md` file ends up being significantly simplified, only calling high-level KZG functions.
Some additional things that this commit does:
- Moves all EIP4844 cryptography into polynomial-commitments.md
- Improves the Fiat-Shamir stack by removing the need for SSZ and by introducing simple domain separators
Co-authored-by: Kevaundray Wedderburn <kevtheappdev@gmail.com>
Co-authored-by: Hsiao-Wei Wang <hsiaowei.eth@gmail.com>
Co-authored-by: Dankrad Feist <mail@dankradfeist.de>
Future light client protocol extensions may include data from the block
in addition to data from the state, e.g., `ExecutionPayloadHeader`.
To prepare for this, also pass the block to the corresponding functions.
In practice, blocks access is easier than historic state access, meaning
there are no practical limitations due to this change.
Add more detailed LC object documentation to explain that the various
merkle proofs are relative to the beacon block's state root.
Likewise, clarify that sync committees relate to the finalized header
(not to the optimistic header, which can be a period ahead).
For LC gossip, the documentation did not specify what slot number to use
for deriving the gossip objects. This missing documentation is now added
to document using `attested_header.slot`.
This PR, a continuation of
replaces `historical_roots` with
`historical_block_roots`.
By keeping an accumulator of historical block roots in the state, it
becomes possible to validate the entire block history that led up to
that particular state without executing the transitions, and without
checking them one by one in backwards order using a parent chain.
This is interesting for archival purposes as well as when implementing
sync protocols that can verify chunks of blocks quickly, meaning they
can be downloaded in any order.
It's also useful as it provides a canonical hash by which such chunks of
blocks can be named, with a direct reference in the state.
In this PR, `historical_roots` is frozen at its current value and
`historical_batches` are computed from the merge epoch onwards.
After this PR, `block_batch_root` in the state can be used to verify an
era of blocks against the state with a simple root check.
The `historical_roots` values on the other hand can be used to verify
that a constant distributed with clients is valid for a particular
state, and therefore extends the block validation all the way back to
genesis without backfilling `block_batch_root` and without introducing
any new security assumptions in the client.
As far as naming goes, it's convenient to talk about an "era" being 8192
slots ~= 1.14 days. The 8192 number comes from the
SLOTS_PER_HISTORICAL_ROOT constant.
With multiple easily verifable blocks in a file, it becomes trivial to
offload block history to out-of-protocol transfer methods (bittorrent /
ftp / whatever) - including execution payloads, paving the way for a
future in which clients purge block history in p2p.
This PR can be applied along with the merge which simplifies payload
distribution from the get-go. Both execution and consensus clients
benefit because from the merge onwards, they both need to be able to
supply ranges of blocks in the sync protocol from what effectively is
"cold storage".
Another possibility is to include it in a future cleanup PR - this
complicates the "cold storage" mode above by not covering exection
payloads from start.
* Remove the work-in-progress note in Bellatrix spec
Bellatrix is done and released.
* Remove work-in-progress notes in Bellatrix specs
* Remove work-in-progress notes in Bellatrix specs
* Remove work-in-progress notes in Bellatrix specs
Improves separation between BLS cryptography and Ethereum SSZ logic.
Now the BLS library just implements bytes_to_bls_field(). Then hash_to_bls_field() does the Ethereum SSZ magic and
calls bytes_to_bls_field().
While the current Altair specs define structures to aid light client
development, one missing key aspect is the network protocol definition.
Certain implementations have started defining their own REST based APIs,
e.g., Lodestar at https://github.com/ChainSafe/lodestar/blob/master/packages/api/src/routes/lightclient.ts
While such APIs are useful, REST does not seem to be the ideomatic
choice as the sole API available at such a low level for Ethereum.
This patch introduces a libp2p based protocol to allow light clients to
sync to the latest `BeaconBlockHeader` in a trustless and decentralized
manner, building on top of prior work from:
- @hwwhww at https://github.com/ethereum/consensus-specs/pull/2267
- @jinfwhuang at https://github.com/ethereum/consensus-specs/pull/2786
- Lodestar's REST API (also has an endpoint to fetch merkle proofs!)
Etan Kissling
Danny Ryan
Hsiao-Wei Wang
henridf
Dankrad Feist
terence tsao
Mikhail Kalinin
Jacek Sieka
dapplion
George Kadianakis
kevaundray
Justin Traglia
Stefan Bratanov
Alex Stokes
Tim Beiko
Roberto Bayardo
Dmitrii Shmatko
Ramana Kumar
Enrico Del Fante
realbigsean
Enrico Del Fante
inphi
Michael Sproul
Potuz
Michael Sproul
ethDreamer
Mark Mackey
Jacek Sieka
Jim McDonald
ethosdev
protolambda
Dustin Brody
Ben Guidarelli
David Theodore