nimbus-eth2/beacon_chain/state_transition.nim

84 lines
3.7 KiB
Nim

# beacon_chain
# Copyright (c) 2018 Status Research & Development GmbH
# Licensed and distributed under either of
# * MIT license (license terms in the root directory or at http://opensource.org/licenses/MIT).
# * Apache v2 license (license terms in the root directory or at http://www.apache.org/licenses/LICENSE-2.0).
# at your option. This file may not be copied, modified, or distributed except according to those terms.
# A imcomplete implementation of the state transition function, as described
# under "Per-block processing" in https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md
#
# The code is here mainly to verify the data types and get an idea about
# missing pieces - needs testing throughout
import
options,
./spec/[beaconstate, crypto, datatypes, digest, helpers],
./ssz,
milagro_crypto # nimble install https://github.com/status-im/nim-milagro-crypto@#master
func checkAttestations(state: BeaconState, blck: BeaconBlock):
seq[ProcessedAttestation] =
discard
func process_block*(state: BeaconState, blck: BeaconBlock): Option[BeaconState] =
## When a new block is received, all participants must verify that the block
## makes sense and update their state accordingly. This function will return
## the new state, unless something breaks along the way
# XXX: simplistic way to be able to rollback state
var state = state
let
parent_hash = blck.ancestor_hashes[0]
slot = blck.slot
parent_slot = slot - 1 # XXX Not!! can skip slots...
# TODO actually get parent block, which means fixing up BeaconState refs above;
# there's no distinction between active/crystallized state anymore, etc.
state.recent_block_hashes =
append_to_recent_block_hashes(state.recent_block_hashes, parent_slot, slot,
parent_hash)
state.pending_attestations.add checkAttestations(state, blck)
doAssert blck.attestations.len <= MAX_ATTESTATION_COUNT
for attestation in blck.attestations:
if attestation.data.slot <= blck.slot - MIN_ATTESTATION_INCLUSION_DELAY:
return
if attestation.data.slot >= max(parent_slot - CYCLE_LENGTH + 1, 0):
return
#doAssert attestation.data.justified_slot == justification_source if attestation.data.slot >= state.last_state_recalculation_slot else prev_cycle_justification_source
# doAssert attestation.data.justified_block_hash == get_block_hash(state, block, attestation.data.justified_slot).
# doAssert either attestation.data.last_crosslink_hash or attestation.data.shard_block_hash equals state.crosslinks[shard].shard_block_hash.
let attestation_participants = get_attestation_participants(
state, attestation.data, attestation.attester_bitfield)
var
agg_pubkey: ValidatorPubKey
empty = true
for attester_idx in attestation_participants:
let validator = state.validators[attester_idx]
if empty:
agg_pubkey = validator.pubkey
empty = false
else:
agg_pubkey.combine(validator.pubkey)
# Verify that aggregate_sig verifies using the group pubkey.
let msg = hashSSZ(attestation.data)
# For now only check compilation
# doAssert attestation.aggregate_sig.verifyMessage(msg, agg_pubkey)
debugEcho "Aggregate sig verify message: ", attestation.aggregate_sig.verifyMessage(msg, agg_pubkey)
return some(state)
# Extend the list of AttestationRecord objects in the active_state, ordering the new additions in the same order as they came in the block.
# TODO
# Verify that the slot % len(get_indices_for_slot(state, slot-1)[0])'th attester in get_indices_for_slot(state, slot-1)[0]is part of at least one of the AttestationRecord objects; this attester can be considered to be the proposer of the block.
# TODO