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>
Etan Kissling
Alex Stokes
Danny Ryan
Hsiao-Wei Wang
George Kadianakis
Tim Beiko
terence tsao
Potuz
Roberto Bayardo
kevaundray