From 54217772fed49499a980b9ac1d947c6a84f52f51 Mon Sep 17 00:00:00 2001 From: vbuterin Date: Mon, 19 Nov 2018 20:13:58 -0500 Subject: [PATCH] Added domain separation --- specs/core/0_beacon-chain.md | 39 ++++++++++++++++++++++++------------ 1 file changed, 26 insertions(+), 13 deletions(-) diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md index 6914c64e7..22c55a997 100644 --- a/specs/core/0_beacon-chain.md +++ b/specs/core/0_beacon-chain.md @@ -90,6 +90,15 @@ The primary source of load on the beacon chain are "attestations". Attestations | `ENTRY` | `0` | | `EXIT` | `1` | +**Domains for BLS signatures** + +| Name | Value | +| - | :-: | +| `DOMAIN_DEPOSIT` | `0` | +| `DOMAIN_ATTESTATION` | `1` | +| `DOMAIN_PROPOSAL` | `2` | +| `DOMAIN_LOGOUT` | `3` | + ### PoW chain registration contract The initial deployment phases of Ethereum 2.0 are implemented without consensus changes to the PoW chain. A registration contract is added to the PoW chain to deposit ETH. This contract has a `registration` function which takes as arguments `pubkey`, `withdrawal_shard`, `withdrawal_address`, `randao_commitment` as defined in a `ValidatorRecord` below. A BLS `proof_of_possession` of types `bytes` is given as a final argument. @@ -152,8 +161,6 @@ An `AttestationSignedData` has the following fields: ```python { - # Fork version - 'fork_version': 'uint64', # Slot number 'slot': 'uint64', # Shard number @@ -652,7 +659,7 @@ The `add_validator` routine is defined below. This routine should be run for every validator that is inducted as part of a log created on the PoW chain [TODO: explain where to check for these logs]. The status of the validators added after genesis is `PENDING_ACTIVATION`. These logs should be processed in the order in which they are emitted by the PoW chain. -First, a helper function: +First, some helper functions: ```python def min_empty_validator(validators: List[ValidatorRecord], current_slot: int): @@ -662,10 +669,15 @@ def min_empty_validator(validators: List[ValidatorRecord], current_slot: int): return None ``` +```python +def get_fork_version(state: State, slot: uint64): + return state.pre_fork_version if slot < state.fork_slot_number else state.post_fork_version +``` + Now, to add a validator: ```python -def add_validator(validators: List[ValidatorRecord], +def add_validator(state: State, pubkey: int, proof_of_possession: bytes, withdrawal_shard: int, @@ -678,7 +690,8 @@ def add_validator(validators: List[ValidatorRecord], signed_message = as_bytes32(pubkey) + as_bytes2(withdrawal_shard) + withdrawal_address + randao_commitment assert BLSVerify(pub=pubkey, msg=hash(signed_message), - sig=proof_of_possession) + sig=proof_of_possession, + domain=get_fork_version(state, current_slot) * 2**32 + DOMAIN_DEPOSIT) # Pubkey uniqueness assert pubkey not in [v.pubkey for v in validators] rec = ValidatorRecord( @@ -815,9 +828,9 @@ For each one of these attestations: * Compute `parent_hashes` = `[get_block_hash(state, block, slot - CYCLE_LENGTH + i) for i in range(1, CYCLE_LENGTH - len(oblique_parent_hashes) + 1)] + oblique_parent_hashes` (eg, if `CYCLE_LENGTH = 4`, `slot = 5`, the actual block hashes starting from slot 0 are `Z A B C D E F G H I J`, and `oblique_parent_hashes = [D', E']` then `parent_hashes = [B, C, D' E']`). Note that when *creating* an attestation for a block, the hash of that block itself won't yet be in the `state`, so you would need to add it explicitly. * Let `attestation_indices` be `get_shards_and_committees_for_slot(state, slot)[x]`, choosing `x` so that `attestation_indices.shard` equals the `shard` value provided to find the set of validators that is creating this attestation record. * Verify that `len(attester_bitfield) == ceil_div8(len(attestation_indices))`, where `ceil_div8 = (x + 7) // 8`. Verify that bits `len(attestation_indices)....` and higher, if present (i.e. `len(attestation_indices)` is not a multiple of 8), are all zero. -* Derive a group public key by adding the public keys of all of the attesters in `attestation_indices` for whom the corresponding bit in `attester_bitfield` (the ith bit is `(attester_bitfield[i // 8] >> (7 - (i %8))) % 2`) equals 1. -* Let `fork_version = pre_fork_version if slot < fork_slot_number else post_fork_version`. -* Verify that `aggregate_sig` verifies using the group pubkey generated and the serialized form of `AttestationSignedData(fork_version, slot, shard, parent_hashes, shard_block_hash, last_crosslinked_hash, shard_block_combined_data_root, justified_slot)` as the message. +* Derive a `group_public_key` by adding the public keys of all of the attesters in `attestation_indices` for whom the corresponding bit in `attester_bitfield` (the ith bit is `(attester_bitfield[i // 8] >> (7 - (i %8))) % 2`) equals 1. +* Let `data = AttestationSignedData(slot, shard, parent_hashes, shard_block_hash, last_crosslinked_hash, shard_block_combined_data_root, justified_slot)` +* Check `BLSVerify(pubkey=group_public_key, msg=data, sig=aggregate_sig, domain=get_fork_version(state, slot) * 2**32 + DOMAIN_ATTESTATION)` Extend the list of `AttestationRecord` objects in the `state` with those included in the block, ordering the new additions in the same order as they came in the block. @@ -843,12 +856,12 @@ For each `SpecialRecord` `obj` in `block.specials`, verify that its `kind` is on ```python { 'validator_index': 'uint64', - 'signature': '[uint256]' + 'signature': '[uint384]' } ``` Perform the following checks: -* Let `fork_version = pre_fork_version if block.slot < fork_slot_number else post_fork_version`. Verify that `BLSVerify(pubkey=validators[data.validator_index].pubkey, msg=hash(LOGOUT_MESSAGE + bytes8(fork_version)), sig=data.signature)` +* Verify that `BLSVerify(pubkey=validators[data.validator_index].pubkey, msg=hash(LOGOUT_MESSAGE + bytes8(fork_version)), sig=data.signature, domain=get_fork_version(state, current_slot) * 2**32 + DOMAIN_LOGOUT)` * Verify that `validators[validator_index].status == ACTIVE`. Run `exit_validator(data.validator_index, state, penalize=False, current_slot=block.slot)`. @@ -859,16 +872,16 @@ Run `exit_validator(data.validator_index, state, penalize=False, current_slot=bl { 'vote1_aggregate_sig_indices': '[uint24]', 'vote1_data': AttestationSignedData, - 'vote1_aggregate_sig': '[uint256]', + 'vote1_aggregate_sig': '[uint384]', 'vote2_aggregate_sig_indices': '[uint24]', 'vote2_data': AttestationSignedData, - 'vote2_aggregate_sig': '[uint256]', + 'vote2_aggregate_sig': '[uint384]', } ``` Perform the following checks: -* For each `aggregate_sig`, verify that `BLSVerify(pubkey=aggregate_pubkey([validators[i].pubkey for i in aggregate_sig_indices]), msg=vote_data, sig=aggsig)` passes. +* For each `aggregate_sig`, verify that `BLSVerify(pubkey=aggregate_pubkey([validators[i].pubkey for i in aggregate_sig_indices]), msg=vote_data, sig=aggsig, domain=get_fork_version(state, vote_data.slot) * 2**32 + DOMAIN_ATTESTATION)` passes. * Verify that `vote1_data != vote2_data`. * Let `intersection = [x for x in vote1_aggregate_sig_indices if x in vote2_aggregate_sig_indices]`. Verify that `len(intersection) >= 1`. * Verify that `vote1_data.justified_slot < vote2_data.justified_slot < vote2_data.slot <= vote1_data.slot`.