# Ethereum 2.0 Phase 1 -- From Phase 0 to Phase 1

**Notice**: This document is a work-in-progress for researchers and implementers.

## Table of contents

<!-- TOC -->

 TODO

<!-- /TOC -->

## Introduction

This document describes the process of moving from Phase 0 to Phase 1 of Ethereum 2.0.

## Configuration

TODO: very unstable/experimental. PLACEHOLDER.

| Name | Value | Unit |
| - | - | - |
| `PHASE_1_FORK_VERSION` | `0x00000001` | `Version` |
| `INITIAL_GASPRICE` | `10` | `Gwei` |

## Fork to Phase 1

### Fork trigger.

TBD. Social consensus, along with state conditions such as epoch boundary, finality, deposits, active validator count, etc. may be part of the decision process to trigger the fork.

### Upgrading the state

After `process_slots` of Phase 0 finishes, but before the first Phase 1 block is processed, an irregular state change is made to upgrade to Phase 1.

```python
def upgrade_to_phase1(pre: phase0.BeaconState) -> BeaconState:
    epoch = get_current_epoch(pre)
    post = BeaconState(
        genesis_time=pre.genesis_time,
        slot=pre.slot,
        fork=Fork(
            previous_version=pre.current_version,
            current_version=PHASE_1_FORK_VERSION,
            epoch=epoch,
        ),
        # History
        latest_block_header=pre.latest_block_header,
        block_roots=pre.block_roots,
        state_roots=pre.state_roots,
        historical_roots=pre.historical_roots,
        # Eth1
        eth1_data=pre.eth1_data,
        eth1_data_votes=pre.eth1_data_votes,
        eth1_deposit_index=pre.eth1_deposit_index,
        # Registry
        validators=List[Validator, VALIDATOR_REGISTRY_LIMIT](
            Validator(
                pubkey=phase0_validator.pubkey,
                withdrawal_credentials=phase0_validator.withdrawal_credentials,
                effective_balance=phase0_validator.effective_balance,
                slashed=phase0_validator.slashed,
                activation_eligibility_epoch=phase0_validator.activation_eligibility_epoch,
                activation_epoch=phase0_validator.activation_eligibility_epoch,
                exit_epoch=phase0_validator.exit_epoch,
                withdrawable_epoch=phase0_validator.withdrawable_epoch,
                next_custody_secret_to_reveal=get_custody_period_for_validator(validator_index, epoch),
                max_reveal_lateness=0,  # TODO custody refactor. Outdated? 
            ) for validator_index, phase0_validator in enumerate(pre.validators)
        ),
        balances=pre.balances,
        # Randomness
        randao_mixes=pre.randao_mixes,
        # Slashings
        slashings=pre.slashings,
        # Attestations
        # previous_epoch_attestations is cleared on upgrade. 
        previous_epoch_attestations=List[PendingAttestation, MAX_ATTESTATIONS * SLOTS_PER_EPOCH](),
        # empty in pre state, since the upgrade is performed just after an epoch boundary.
        current_epoch_attestations=List[PendingAttestation, MAX_ATTESTATIONS * SLOTS_PER_EPOCH](),
        # Finality
        justification_bits=pre.justification_bits,
        previous_justified_checkpoint=pre.previous_justified_checkpoint,
        current_justified_checkpoint=pre.current_justified_checkpoint,
        finalized_checkpoint=pre.finalized_checkpoint,
        # Phase 1
        shard_states=List[ShardState, MAX_SHARDS](
            ShardState(
                slot=0,
                gasprice=INITIAL_GASPRICE,
                data=Root(),
                latest_block_root=Hash(),
            ) for i in range(ACTIVE_SHARDS)
        ),
        online_countdown=Bytes[VALIDATOR_REGISTRY_LIMIT](
            ONLINE_PERIOD for i in range(len(pre.validators))
        ),
        current_light_committee=CompactCommittee(),  # computed after state creation
        next_light_committee=CompactCommittee(),
        # Custody game
        custody_challenge_index=0,
        exposed_derived_secrets=Vector[List[ValidatorIndex, MAX_EARLY_DERIVED_SECRET_REVEALS * SLOTS_PER_EPOCH],
                                       EARLY_DERIVED_SECRET_PENALTY_MAX_FUTURE_EPOCHS]()
    )
    post.current_light_committee = get_light_client_committee(post, post.epoch)
    post.next_light_committee = get_light_client_committee(post, post.epoch + 1)
    return post
```