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aggregate builder and proposer for simplified typing and optimized verification

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protolambda 2021-06-21 00:55:45 +02:00
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specs/sharding/beacon-chain.md
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@ -34,15 +34,8 @@
- [`ShardBlobHeader`](#shardblobheader) - [`ShardBlobHeader`](#shardblobheader)
- [`SignedShardBlob`](#signedshardblob) - [`SignedShardBlob`](#signedshardblob)
- [`SignedShardBlobHeader`](#signedshardblobheader) - [`SignedShardBlobHeader`](#signedshardblobheader)
- [ShardBlock](#shardblock)
- [`ShardBlockHeader`](#shardblockheader)
- [`SignedShardBlock`](#signedshardblock)
- [`SignedShardBlockHeader`](#signedshardblockheader)
- [`PendingShardHeader`](#pendingshardheader) - [`PendingShardHeader`](#pendingshardheader)
- [`ShardBlobReference`](#shardblobreference) - [`ShardBlobReference`](#shardblobreference)
- [`SignedShardBlobReference`](#signedshardblobreference)
- [`ShardBlockReference`](#shardblockreference)
- [`SignedShardBlockReference`](#signedshardblockreference)
- [`ShardProposerSlashing`](#shardproposerslashing) - [`ShardProposerSlashing`](#shardproposerslashing)
- [`ShardWork`](#shardwork) - [`ShardWork`](#shardwork)
- [Helper functions](#helper-functions) - [Helper functions](#helper-functions)
@ -116,8 +109,7 @@ The following values are (non-configurable) constants used throughout the specif
| Name | Value | | Name | Value |
| - | - | | - | - |
| `DOMAIN_SHARD_PROPOSER` | `DomainType('0x80000000')` | | `DOMAIN_SHARD_BLOB` | `DomainType('0x80000000')` |
| `DOMAIN_SHARD_BUILDER` | `DomainType('0x81000000')` |
### Shard Work Status ### Shard Work Status
@ -247,8 +239,6 @@ class ShardBlobBody(Container):
data: List[BLSPoint, POINTS_PER_SAMPLE * MAX_SAMPLES_PER_BLOCK] data: List[BLSPoint, POINTS_PER_SAMPLE * MAX_SAMPLES_PER_BLOCK]
# Latest block root of the Beacon Chain, before shard_blob.slot # Latest block root of the Beacon Chain, before shard_blob.slot
beacon_block_root: Root beacon_block_root: Root
# Builder of the data, pays data-fee to proposer
builder_index: BuilderIndex
# TODO: fee payment amount fields (EIP 1559 like) # TODO: fee payment amount fields (EIP 1559 like)
``` ```
@ -269,8 +259,6 @@ class ShardBlobBodySummary(Container):
data_root: Root data_root: Root
# Latest block root of the Beacon Chain, before shard_blob.slot # Latest block root of the Beacon Chain, before shard_blob.slot
beacon_block_root: Root beacon_block_root: Root
# Builder of the data, pays data-fee to proposer
builder_index: BuilderIndex
# TODO: fee payment amount fields (EIP 1559 like) # TODO: fee payment amount fields (EIP 1559 like)
``` ```
@ -282,18 +270,26 @@ class ShardBlobBodySummary(Container):
class ShardBlob(Container): class ShardBlob(Container):
slot: Slot slot: Slot
shard: Shard shard: Shard
# Proposer of the shard-blob
proposer_index: ValidatorIndex
# Builder of the data, pays data-fee to proposer
builder_index: BuilderIndex
# Blob contents # Blob contents
body: ShardBlobBody body: ShardBlobBody
``` ```
### `ShardBlobHeader` ### `ShardBlobHeader`
Header version of `ShardBlob`. Separates designation (slot, shard) and contents (blob). Header version of `ShardBlob`.
```python ```python
class ShardBlobHeader(Container): class ShardBlobHeader(Container):
slot: Slot slot: Slot
shard: Shard shard: Shard
# Proposer of the shard-blob
proposer_index: ValidatorIndex
# Builder of the data, pays data-fee to proposer
builder_index: BuilderIndex
# Blob contents, without the full data # Blob contents, without the full data
body_summary: ShardBlobBodySummary body_summary: ShardBlobBodySummary
``` ```
@ -316,53 +312,8 @@ Shard proposers can accept `SignedShardBlobHeader` as a data-transaction.
```python ```python
class SignedShardBlobHeader(Container): class SignedShardBlobHeader(Container):
message: ShardBlobHeader message: ShardBlobHeader
signature: BLSSignature # Signature by builder.
``` # Once accepted by proposer, the signatures is the aggregate of both.
### ShardBlock
Full blob data signed by builder, to be confirmed by proxy as `ShardBlockHeader`.
```python
class ShardBlock(Container):
# Shard data with fee payment by bundle builder
signed_blob: SignedShardBlob
# Proposer of the shard-blob
proposer_index: ValidatorIndex
```
### `ShardBlockHeader`
Header version of `ShardBlock`, selecting a `SignedShardBlobHeader`.
```python
class ShardBlockHeader(Container):
# Shard commitments and fee payment by blob builder
signed_blob_header: SignedShardBlobHeader
# Proposer of the shard-blob
proposer_index: ValidatorIndex
```
### `SignedShardBlock`
Shard blob, signed for payment, and signed for proposal. Propagated to attesters.
```python
class SignedShardBlock(Container):
message: ShardBlock
signature: BLSSignature
```
### `SignedShardBlockHeader`
Header version of `SignedShardBlock`, substituting the full data within the blob for just the hash-tree-root.
The signature is equally applicable to `SignedShardBlock`,
which the builder can publish as soon as the signed header is seen.
```python
class SignedShardBlockHeader(Container):
message: ShardBlockHeader
signature: BLSSignature signature: BLSSignature
``` ```
@ -390,44 +341,26 @@ Reference version of `ShardBlobHeader`, substituting the body for just a hash-tr
class ShardBlobReference(Container): class ShardBlobReference(Container):
slot: Slot slot: Slot
shard: Shard shard: Shard
# Blob hash-tree-root for reference, enough for uniqueness
body_root: Root
```
### `SignedShardBlobReference`
`ShardBlobReference`, signed by the blob builder. The builder-signature is part of the block identity.
```python
class SignedShardBlobReference(Container):
message: ShardBlobReference
signature: BLSSignature
```
### `ShardBlockReference`
```python
class ShardBlockReference(Container):
# Blob, minimized for efficient slashing
signed_blob_reference: SignedShardBlobReference
# Proposer of the shard-blob # Proposer of the shard-blob
proposer_index: ValidatorIndex proposer_index: ValidatorIndex
``` # Builder of the data
builder_index: BuilderIndex
### `SignedShardBlockReference` # Blob hash-tree-root for slashing reference
body_root: Root
```python
class SignedShardBlockReference(Container):
message: ShardBlockReference
signature: BLSSignature
``` ```
### `ShardProposerSlashing` ### `ShardProposerSlashing`
```python ```python
class ShardProposerSlashing(Container): class ShardProposerSlashing(Container):
signed_reference_1: SignedShardBlockReference slot: Slot
signed_reference_2: SignedShardBlockReference shard: Shard
proposer_index: ValidatorIndex
builder_index: BuilderIndex
body_root_1: Root
body_root_2: Root
signature_1: BLSSignature
signature_2: BLSSignature
``` ```
### `ShardWork` ### `ShardWork`
@ -552,7 +485,7 @@ def get_shard_proposer_index(beacon_state: BeaconState, slot: Slot, shard: Shard
Return the proposer's index of shard block at ``slot``. Return the proposer's index of shard block at ``slot``.
""" """
epoch = compute_epoch_at_slot(slot) epoch = compute_epoch_at_slot(slot)
seed = hash(get_seed(beacon_state, epoch, DOMAIN_SHARD_PROPOSER) + uint_to_bytes(slot) + uint_to_bytes(shard)) seed = hash(get_seed(beacon_state, epoch, DOMAIN_SHARD_BLOB) + uint_to_bytes(slot) + uint_to_bytes(shard))
# Proposer must have sufficient balance to pay for worst case fee burn # Proposer must have sufficient balance to pay for worst case fee burn
EFFECTIVE_BALANCE_MAX_DOWNWARD_DEVIATION = ( EFFECTIVE_BALANCE_MAX_DOWNWARD_DEVIATION = (
@ -717,12 +650,10 @@ def charge_builder(state: BeaconState, index: BuilderIndex, fee: Gwei) -> None:
##### `process_shard_header` ##### `process_shard_header`
```python ```python
def process_shard_header(state: BeaconState, signed_block_header: SignedShardBlockHeader) -> None: def process_shard_header(state: BeaconState, signed_header: SignedShardBlobHeader) -> None:
block_header: ShardBlockHeader = signed_block_header.message header: ShardBlobHeader = signed_header.message
signed_blob_header: SignedShardBlobHeader = block_header.signed_blob_header slot = header.slot
blob_header: ShardBlobHeader = signed_blob_header.message shard = header.shard
slot = blob_header.slot
shard = blob_header.shard
# Verify the header is not 0, and not from the future. # Verify the header is not 0, and not from the future.
assert Slot(0) < slot <= state.slot assert Slot(0) < slot <= state.slot
@ -733,7 +664,7 @@ def process_shard_header(state: BeaconState, signed_block_header: SignedShardBlo
assert shard < get_active_shard_count(state, header_epoch) assert shard < get_active_shard_count(state, header_epoch)
# Verify that the block root matches, # Verify that the block root matches,
# to ensure the header will only be included in this specific Beacon Chain sub-tree. # to ensure the header will only be included in this specific Beacon Chain sub-tree.
assert blob_header.body_summary.beacon_block_root == get_block_root_at_slot(state, slot - 1) assert header.body_summary.beacon_block_root == get_block_root_at_slot(state, slot - 1)
# Check that this data is still pending # Check that this data is still pending
committee_work = state.shard_buffer[slot % SHARD_STATE_MEMORY_SLOTS][shard] committee_work = state.shard_buffer[slot % SHARD_STATE_MEMORY_SLOTS][shard]
@ -741,24 +672,17 @@ def process_shard_header(state: BeaconState, signed_block_header: SignedShardBlo
# Check that this header is not yet in the pending list # Check that this header is not yet in the pending list
current_headers: List[PendingShardHeader, MAX_SHARD_HEADERS_PER_SHARD] = committee_work.status.value current_headers: List[PendingShardHeader, MAX_SHARD_HEADERS_PER_SHARD] = committee_work.status.value
header_root = hash_tree_root(block_header) header_root = hash_tree_root(header)
assert header_root not in [pending_header.root for pending_header in current_headers] assert header_root not in [pending_header.root for pending_header in current_headers]
# Verify proposer # Verify proposer matches
assert block_header.proposer_index == get_shard_proposer_index(state, slot, shard) assert header.proposer_index == get_shard_proposer_index(state, slot, shard)
# Verify proposer signature
block_signing_root = compute_signing_root(block_header, get_domain(state, DOMAIN_SHARD_PROPOSER))
proposer_pubkey = state.validators[block_header.proposer_index].pubkey
assert bls.Verify(proposer_pubkey, block_signing_root, signed_block_header.signature)
# Verify builder requirements # Verify builder and proposer aggregate signature
blob_summary: ShardBlobBodySummary = blob_header.body_summary blob_signing_root = compute_signing_root(header, get_domain(state, DOMAIN_SHARD_BLOB))
builder_index = blob_summary.builder_index builder_pubkey = state.builders[header.builder_index].pubkey
proposer_pubkey = state.validators[header.proposer_index].pubkey
# Verify builder signature assert bls.FastAggregateVerify([builder_pubkey, proposer_pubkey], blob_signing_root, signed_header.signature)
builder = state.builders[builder_index]
blob_signing_root = compute_signing_root(blob_header, get_domain(state, DOMAIN_SHARD_BUILDER)) # TODO new constant
assert bls.Verify(builder.pubkey, blob_signing_root, signed_blob_header.signature)
# Verify the length by verifying the degree. # Verify the length by verifying the degree.
body_summary = header.body_summary body_summary = header.body_summary
@ -771,10 +695,10 @@ def process_shard_header(state: BeaconState, signed_block_header: SignedShardBlo
# Charge builder, with hard balance requirement # Charge builder, with hard balance requirement
fee = Gwei(123) # TODO EIP 1559 like fee? Burn some of it? fee = Gwei(123) # TODO EIP 1559 like fee? Burn some of it?
charge_builder(state, builder_index, fee) charge_builder(state, header.builder_index, fee)
# TODO: proposer is charged for confirmed headers (see charge_confirmed_shard_fees). # TODO: proposer is charged for confirmed headers (see charge_confirmed_shard_fees).
# Need to align incentive, so proposer does not gain from including unconfirmed headers # Need to align incentive, so proposer does not gain from including unconfirmed headers
increase_balance(state, block_header.proposer_index, fee) increase_balance(state, blob_header.proposer_index, fee)
# Initialize the pending header # Initialize the pending header
index = compute_committee_index_from_shard(state, slot, shard) index = compute_committee_index_from_shard(state, slot, shard)
@ -801,32 +725,33 @@ The goal is to ensure that a proof can only be constructed if `deg(B) < l` (ther
```python ```python
def process_shard_proposer_slashing(state: BeaconState, proposer_slashing: ShardProposerSlashing) -> None: def process_shard_proposer_slashing(state: BeaconState, proposer_slashing: ShardProposerSlashing) -> None:
reference_1: ShardBlockReference = proposer_slashing.signed_reference_1.message # Verify the headers are different
reference_2 : ShardBlockReference = proposer_slashing.signed_reference_2.message assert proposer_slashing.body_root_1 != proposer_slashing.body_root_2
blob_1 = reference_1.signed_blob_reference.message
blob_2 = reference_2.signed_blob_reference.message slot = proposer_slashing.slot
shard = proposer_slashing.shard
proposer_index = proposer_slashing.proposer_index
builder_index = proposer_slashing.builder_index
# Verify header slots match
assert blob_1.slot == blob_2.slot
# Verify header shards match
assert blob_1.shard == blob_2.shard
# Verify header proposer indices match
assert reference_1.proposer_index == reference_2.proposer_index
# Verify the headers are different (i.e. different body, or different builder signature)
assert (
blob_1.body_root != blob_2.body_root
or reference_1.signed_blob_reference.signature != reference_2.signed_blob_reference.signature
)
# Verify the proposer is slashable # Verify the proposer is slashable
proposer = state.validators[reference_1.proposer_index] proposer = state.validators[proposer_index]
assert is_slashable_validator(proposer, get_current_epoch(state)) assert is_slashable_validator(proposer, get_current_epoch(state))
# Verify signatures
for signed_header in (proposer_slashing.signed_reference_1, proposer_slashing.signed_reference_2):
domain = get_domain(state, DOMAIN_SHARD_PROPOSER, compute_epoch_at_slot(signed_header.message.slot))
signing_root = compute_signing_root(signed_header.message, domain)
assert bls.Verify(proposer.pubkey, signing_root, signed_header.signature)
slash_validator(state, reference_1.proposer_index) reference_1 = ShardBlobReference(slot=slot, shard=shard,
proposer_index=proposer_index, builder_index=builder_index,
body_root= proposer_slashing.body_root_1)
reference_2 = ShardBlobReference(slot=slot, shard=shard,
proposer_index=proposer_index, builder_index=builder_index,
body_root= proposer_slashing.body_root_2)
proposer_pubkey = proposer.pubkey
builder_pubkey = state.builders[builder_index].pubkey
domain = get_domain(state, DOMAIN_SHARD_PROPOSER, compute_epoch_at_slot(slot))
signing_root_1 = compute_signing_root(reference_1, domain)
signing_root_2 = compute_signing_root(reference_2, domain)
assert bls.FastAggregateVerify([builder_pubkey, proposer_pubkey], signing_root_1, proposer_slashing.signature_1)
assert bls.FastAggregateVerify([builder_pubkey, proposer_pubkey], signing_root_2, proposer_slashing.signature_2)
slash_validator(state, proposer_index)
``` ```
### Epoch transition ### Epoch transition