add genesis_validators_root to beaconstate and utilize in sig domain separation as well as fork separation

setup.py

@@ -95,7 +95,7 @@ from dataclasses import (
 from eth2spec.utils.ssz.ssz_impl import hash_tree_root
 from eth2spec.utils.ssz.ssz_typing import (
     View, boolean, Container, List, Vector, uint64,
-    Bytes1, Bytes4, Bytes8, Bytes32, Bytes48, Bytes96, Bitlist, Bitvector,
+    Bytes1, Bytes4, Bytes32, Bytes48, Bytes96, Bitlist, Bitvector,
 )
 from eth2spec.utils import bls
 
@@ -117,7 +117,7 @@ from dataclasses import (
 from eth2spec.utils.ssz.ssz_impl import hash_tree_root
 from eth2spec.utils.ssz.ssz_typing import (
     View, boolean, Container, List, Vector, uint64, uint8, bit,
-    ByteList, Bytes1, Bytes4, Bytes8, Bytes32, Bytes48, Bytes96, Bitlist, Bitvector,
+    ByteList, Bytes1, Bytes4, Bytes32, Bytes48, Bytes96, Bitlist, Bitvector,
 )
 from eth2spec.utils import bls
 

specs/phase0/beacon-chain.md

@@ -149,7 +149,7 @@ We define the following Python custom types for type hinting and readability:
 | `Root` | `Bytes32` | a Merkle root |
 | `Version` | `Bytes4` | a fork version number |
 | `DomainType` | `Bytes4` | a domain type |
-| `Domain` | `Bytes8` | a signature domain |
+| `Domain` | `Bytes32` | a signature domain |
 | `BLSPubkey` | `Bytes48` | a BLS12-381 public key |
 | `BLSSignature` | `Bytes96` | a BLS12-381 signature |
 
@@ -473,6 +473,7 @@ class BeaconBlock(Container):
 class BeaconState(Container):
     # Versioning
     genesis_time: uint64
+    genesis_validators_root: Root
     slot: Slot
     fork: Fork
     # History
@@ -795,13 +796,15 @@ def compute_activation_exit_epoch(epoch: Epoch) -> Epoch:
 #### `compute_domain`
 
 ```python
-def compute_domain(domain_type: DomainType, fork_version: Optional[Version]=None) -> Domain:
+def compute_domain(domain_type: DomainType, fork_version: Optional[Version]=None, genesis_root: Root=None) -> Domain:
     """
     Return the domain for the ``domain_type`` and ``fork_version``.
     """
     if fork_version is None:
         fork_version = GENESIS_FORK_VERSION
-    return Domain(domain_type + fork_version)
+    if genesis_root is None:
+        genesis_root = Root()
+    return Domain(domain_type + fork_version + genesis_root[:24])
 ```
 
 #### `compute_signing_root`
@@ -977,7 +980,7 @@ def get_domain(state: BeaconState, domain_type: DomainType, epoch: Epoch=None) -
     """
     epoch = get_current_epoch(state) if epoch is None else epoch
     fork_version = state.fork.previous_version if epoch < state.fork.epoch else state.fork.current_version
-    return compute_domain(domain_type, fork_version)
+    return compute_domain(domain_type, fork_version, state.genesis_validators_root)
 ```
 
 #### `get_indexed_attestation`
@@ -1122,6 +1125,9 @@ def initialize_beacon_state_from_eth1(eth1_block_hash: Bytes32,
             validator.activation_eligibility_epoch = GENESIS_EPOCH
             validator.activation_epoch = GENESIS_EPOCH
 
+    # Set genesis validators root for domain separation and chain versioning
+    state.genesis_validators_root = hash_tree_root(state.validators)
+
     return state
 ```
 

specs/phase0/p2p-interface.md

@@ -615,23 +615,37 @@ ENRs MUST carry a generic `eth2` key with an 16-byte value of the node's current
 |:-------------|:--------------------|
 | `eth2`       | SSZ `ENRForkID`        |
 
-Specifically, the value of the `eth2` key MUST be the following SSZ encoded object (`ENRForkID`), where
+First we define `current_fork` as the following SSZ encoded object
 
 ```
 (
-    current_fork_version: Fork
-    next_fork_version: Fork
+    current_fork_version: Version
+    genesis_validators_root: Root
+)
+```
+
+where
+
+* `current_fork_version` is the fork version at the node's current epoch defined by the wall-clock time (not necessarily the epoch to which the node is sync)
+* `genesis_validators_root` is the static `Root` found in `state.genesis_validators_root`
+
+Specifically, the value of the `eth2` key MUST be the following SSZ encoded object (`ENRForkID`)
+
+```
+(
+    current_fork_digest: Bytes4
+    next_fork_version: Version
     next_fork_epoch: Epoch
 )
 ```
 
 where the fields of `ENRForkID` are defined as
 
-* `current_fork_version` is the fork version at the node's current epoch defined by the wall-clock time (not necessarily the epoch to which the node is sync)
+* `current_fork_digest` is `hash_tree_root(current_fork)[:4]`
 * `next_fork_version` is the fork version corresponding to the next planned hard fork at a future epoch. If no future fork is planned, set `next_fork_version = current_fork_version` to signal this fact
 * `next_fork_epoch` is the epoch at which the next fork is planned and the `current_fork_version` will be updated. If no future fork is planned, set `next_fork_epoch = FAR_FUTURE_EPOCH` to signal this fact
 
-Clients SHOULD connect to peers with `current_fork_version`, `next_fork_version`, and `next_fork_epoch` that match local values.
+Clients SHOULD connect to peers with `current_fork_digest`, `next_fork_version`, and `next_fork_epoch` that match local values.
 
 Clients MAY connect to peers with the same `current_fork_version` but a different `next_fork_version`/`next_fork_epoch`. Unless `ENRForkID` is manually updated to matching prior to the earlier `next_fork_epoch` of the two clients, these type of connecting clients will be unable to successfully interact starting at the earlier `next_fork_epoch`.
 

specs/phase1/beacon-chain.md

@@ -244,6 +244,7 @@ Note that aside from the new additions, `Validator` and `PendingAttestation` hav
 class BeaconState(Container):
     # Versioning
     genesis_time: uint64
+    genesis_validators_root: Root
     slot: Slot
     fork: Fork
     # History

tests/core/pyspec/eth2spec/test/helpers/genesis.py

@@ -43,4 +43,7 @@ def create_genesis_state(spec, validator_balances, activation_threshold):
             validator.activation_eligibility_epoch = spec.GENESIS_EPOCH
             validator.activation_epoch = spec.GENESIS_EPOCH
 
+    # Set genesis validators root for domain separation and chain versioning
+    state.genesis_validators_root = spec.hash_tree_root(state.validators)
+
     return state