Beacon Chain Spec: Message processing

In the initial validation

store.time >= (attestation_slot + 1) * SECONDS_PER_SLOT

Attestations can only affect the fork choice of subsequent slots.

store.time >= pre_state.genesis_time + block.slot * SECONDS_PER_SLOT

Blocks cannot be in the future. If they are, their consideration must be delayed until the are in the past.

In the Beacon state transition

attestation_slot + MIN_ATTESTATION_INCLUSION_DELAY <= state.slot <= attestation_slot + SLOTS_PER_EPOCH

data.target.epoch in (get_previous_epoch(state), get_current_epoch(state))

Also, the source epoch must be the justified checkpoint in the current or previous checkpoint

block.slot == state.slot

This enforce all attestations must vote for the correct checkpoint (the epoch boundary block in this slot)

If there are skip slots, the block root of the slot is the one of the latest block

code: Python

def process_slots(state: BeaconState, slot: Slot) -> None:

assert state.slot <= slot

while state.slot < slot:

process_slot(state)

# Process epoch on the start slot of the next epoch

if (state.slot + 1) % SLOTS_PER_EPOCH == 0:

process_epoch(state)

state.slot += Slot(1)