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nimbus-eth2/beacon_chain/spec/eip7594_helpers.nim

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# beacon_chain
# Copyright (c) 2018-2024 Status Research & Development GmbH
# Licensed and distributed under either of
# * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
# * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
# at your option. This file may not be copied, modified, or distributed except according to those terms.
{.push raises: [].}
# Uncategorized helper functions from the spec
import
std/algorithm,
results,
eth/p2p/discoveryv5/[node],
kzg4844/[kzg],
ssz_serialization/[
proofs,
types],
./crypto,
./[helpers, digest],
./datatypes/[fulu]
type
CellBytes = array[fulu.CELLS_PER_EXT_BLOB, Cell]
ProofBytes = array[fulu.CELLS_PER_EXT_BLOB, KzgProof]
func sortedColumnIndices(columnsPerSubnet: ColumnIndex,
subnetIds: HashSet[uint64]):
seq[ColumnIndex] =
var res: seq[ColumnIndex] = @[]
for i in 0'u64 ..< columnsPerSubnet:
for subnetId in subnetIds:
let index = DATA_COLUMN_SIDECAR_SUBNET_COUNT * i + subnetId
res.add(ColumnIndex(index))
res.sort
res
func sortedColumnIndexList(columnsPerSubnet: ColumnIndex,
subnetIds: HashSet[uint64]):
List[ColumnIndex, NUMBER_OF_COLUMNS] =
var
res: seq[ColumnIndex]
for i in 0'u64 ..< columnsPerSubnet:
for subnetId in subnetIds:
let index = DATA_COLUMN_SIDECAR_SUBNET_COUNT * i + subnetId
res.add(ColumnIndex(index))
res.sort()
List[ColumnIndex, NUMBER_OF_COLUMNS].init(res)
func get_custody_column_subnets*(node_id: NodeId,
custody_subnet_count: uint64):
HashSet[uint64] =
# Decouples the custody subnet computation part from
# `get_custody_columns`, in order to later use this subnet list
# in order to maintain subscription to specific column subnets.
var
subnet_ids: HashSet[uint64]
current_id = node_id
while subnet_ids.lenu64 < custody_subnet_count:
var
hashed_bytes: array[8, byte]
let
current_id_bytes = current_id.toBytesLE()
hashed_current_id = eth2digest(current_id_bytes)
hashed_bytes[0..7] = hashed_current_id.data.toOpenArray(0,7)
let subnet_id = bytes_to_uint64(hashed_bytes) mod
DATA_COLUMN_SIDECAR_SUBNET_COUNT
subnet_ids.incl(subnet_id)
if current_id == UInt256.high.NodeId:
# Overflow prevention
current_id = NodeId(StUint[256].zero)
current_id += NodeId(StUint[256].one)
subnet_ids
# https://github.com/ethereum/consensus-specs/blob/v1.5.0-alpha.5/specs/_features/eip7594/das-core.md#get_custody_columns
func get_custody_columns*(node_id: NodeId,
custody_subnet_count: uint64):
seq[ColumnIndex] =
let
subnet_ids =
get_custody_column_subnets(node_id, custody_subnet_count)
const
columns_per_subnet =
NUMBER_OF_COLUMNS div DATA_COLUMN_SIDECAR_SUBNET_COUNT
sortedColumnIndices(ColumnIndex(columns_per_subnet), subnet_ids)
func get_custody_columns_set*(node_id: NodeId,
custody_subnet_count: uint64):
HashSet[ColumnIndex] =
# This method returns a HashSet of column indices,
# the method is specifically relevant while peer filtering
let
subnet_ids =
get_custody_column_subnets(node_id, custody_subnet_count)
const
columns_per_subnet =
NUMBER_OF_COLUMNS div DATA_COLUMN_SIDECAR_SUBNET_COUNT
sortedColumnIndices(ColumnIndex(columns_per_subnet), subnet_ids).toHashSet()
func get_custody_column_list*(node_id: NodeId,
custody_subnet_count: uint64):
List[ColumnIndex, NUMBER_OF_COLUMNS] =
# Not in spec in the exact format, but it is useful in sorting custody columns
# before sending, data_column_sidecars_by_range requests
let
subnet_ids =
get_custody_column_subnets(node_id, custody_subnet_count)
const
columns_per_subnet =
NUMBER_OF_COLUMNS div DATA_COLUMN_SIDECAR_SUBNET_COUNT
sortedColumnIndexList(ColumnIndex(columns_per_subnet), subnet_ids)
# https://github.com/ethereum/consensus-specs/blob/v1.5.0-alpha.5/specs/_features/eip7594/das-core.md#compute_matrix
proc compute_matrix*(blobs: seq[KzgBlob]): Result[seq[MatrixEntry], cstring] =
## `compute_matrix` helper demonstrates the relationship
## between blobs and the `MatrixEntries`
var extended_matrix: seq[MatrixEntry]
for blbIdx, blob in blobs.pairs:
let cellsAndProofs = computeCellsAndKzgProofs(blob)
if cellsAndProofs.isErr:
return err("Computing Extended Matrix: Issue computing cells and proofs")
for i in 0..<fulu.CELLS_PER_EXT_BLOB:
extended_matrix.add(MatrixEntry(
cell: cellsAndProofs.get.cells[i],
kzg_proof: cellsAndProofs.get.proofs[i],
row_index: blbIdx.uint64,
column_index: i.uint64
))
ok(extended_matrix)
# https://github.com/ethereum/consensus-specs/blob/v1.5.0-alpha.5/specs/_features/eip7594/das-core.md#recover_matrix
proc recover_matrix*(partial_matrix: seq[MatrixEntry],
blobCount: int):
Result[seq[MatrixEntry], cstring] =
## This helper demonstrates how to apply recover_cells_and_kzg_proofs
## The data structure for storing cells is implementation-dependent
var extended_matrix: seq[MatrixEntry]
for blob_index in 0..<blobCount:
var
cell_indices: seq[CellIndex]
cells: seq[Cell]
for e in partial_matrix:
if e.row_index == uint64(blob_index):
cell_indices.add(e.column_index)
cells.add(e.cell)
let recoveredCellsAndKzgProofs =
recoverCellsAndKzgProofs(cell_indices, cells)
if recoveredCellsAndKzgProofs.isErr:
return err("Issue in recovering cells and proofs")
for i in 0..<recoveredCellsAndKzgProofs.get.cells.len:
let
cell = recoveredCellsAndKzgProofs.get.cells[i]
proof = recoveredCellsAndKzgProofs.get.proofs[i]
extended_matrix.add(MatrixEntry(
cell: cell,
kzg_proof: proof,
row_index: blob_index.uint64,
column_index: i.uint64
))
ok(extended_matrix)
# https://github.com/ethereum/consensus-specs/blob/v1.5.0-alpha.9/specs/_features/eip7594/das-core.md#get_data_column_sidecars
proc get_data_column_sidecars*(signed_beacon_block: electra.TrustedSignedBeaconBlock,
cellsAndProofs: seq[CellsAndProofs]):
seq[DataColumnSidecar] =
## Given a trusted signed beacon block and the cells/proofs associated
## with each data column (thereby blob as well) corresponding to the block,
## this function assembles the sidecars which can be distributed to
## the peers post data column reconstruction at every slot start.
##
## Note: this function only accepts `TrustedSignedBeaconBlock` as
## during practice we would be computing cells and proofs from
## data columns only after retrieving them from the database, where
## they we were already verified and persisted.
template blck(): auto = signed_beacon_block.message
let
beacon_block_header =
BeaconBlockHeader(
slot: blck.slot,
proposer_index: blck.proposer_index,
parent_root: blck.parent_root,
state_root: blck.state_root,
body_root: hash_tree_root(blck.body))
signed_beacon_block_header =
SignedBeaconBlockHeader(
message: beacon_block_header,
signature: signed_beacon_block.signature.toValidatorSig)
var
sidecars =
newSeqOfCap[DataColumnSidecar](CELLS_PER_EXT_BLOB)
for column_index in 0..<NUMBER_OF_COLUMNS:
var
column_cells: seq[KzgCell]
column_proofs: seq[KzgProof]
for i in 0..<cellsAndProofs.len:
column_cells.add(cellsAndProofs[i].cells)
column_proofs.add(cellsAndProofs[i].proofs)
var sidecar = DataColumnSidecar(
index: ColumnIndex(column_index),
column: DataColumn.init(column_cells),
kzg_commitments: blck.body.blob_kzg_commitments,
kzg_proofs: KzgProofs.init(column_proofs),
signed_block_header: signed_beacon_block_header)
blck.body.build_proof(
KZG_COMMITMENTS_INCLUSION_PROOF_DEPTH_GINDEX.GeneralizedIndex,
sidecar.kzg_commitments_inclusion_proof).expect("Valid gindex")
sidecars.add(sidecar)
sidecars
# Alternative approach to `get_data_column_sidecars` by directly computing
# blobs from blob bundles
proc get_data_column_sidecars*(signed_beacon_block: electra.SignedBeaconBlock,
blobs: seq[KzgBlob]):
Result[seq[DataColumnSidecar], string] =
## Given a signed beacon block and the blobs corresponding to the block,
## this function assembles the sidecars which can be distributed to
## the peers post data column reconstruction at every slot start.
##
## Note: this function only accepts `SignedBeaconBlock` as
## during practice we would be extracting data columns
## before publishing them, all of this happens during block
## production, hence the blocks are yet untrusted and have not
## yet been verified.
template blck(): auto = signed_beacon_block.message
let
beacon_block_header =
BeaconBlockHeader(
slot: blck.slot,
proposer_index: blck.proposer_index,
parent_root: blck.parent_root,
state_root: blck.state_root,
body_root: hash_tree_root(blck.body))
signed_beacon_block_header =
SignedBeaconBlockHeader(
message: beacon_block_header,
signature: signed_beacon_block.signature)
var
sidecars =
newSeqOfCap[DataColumnSidecar](CELLS_PER_EXT_BLOB)
cells = newSeq[CellBytes](blobs.len)
proofs = newSeq[ProofBytes](blobs.len)
for i in 0..<blobs.len:
let
cell_and_proof = computeCellsAndKzgProofs(blobs[i])
if cell_and_proof.isErr():
return err("EIP7549: Could not compute cells")
cells[i] = cell_and_proof.get.cells
proofs[i] = cell_and_proof.get.proofs
for columnIndex in 0..<CELLS_PER_EXT_BLOB:
var
column: seq[KzgCell]
kzgProofOfColumn: seq[KzgProof]
for rowIndex in 0..<blobs.len:
column.add(cells[rowIndex][columnIndex])
kzgProofOfColumn.add(proofs[rowIndex][columnIndex])
var sidecar = DataColumnSidecar(
index: ColumnIndex(columnIndex),
column: DataColumn.init(column),
kzg_commitments: blck.body.blob_kzg_commitments,
kzg_proofs: KzgProofs.init(kzgProofOfColumn),
signed_block_header: signed_beacon_block_header)
blck.body.build_proof(
KZG_COMMITMENTS_INCLUSION_PROOF_DEPTH_GINDEX.GeneralizedIndex,
sidecar.kzg_commitments_inclusion_proof).expect("Valid gindex")
sidecars.add(sidecar)
ok(sidecars)
# https://github.com/ethereum/consensus-specs/blob/v1.5.0-alpha.9/specs/_features/eip7594/peer-sampling.md#get_extended_sample_count
func get_extended_sample_count*(samples_per_slot: int,
allowed_failures: int):
int =
## `get_extended_sample_count` computes the number of samples we
## should query from peers, given the SAMPLES_PER_SLOT and
## the number of allowed failures
# If 50% of the columns are missing, we are able to reconstruct the data
# If 50% + 1 columns are missing, we cannot reconstruct the data
const worstCaseConditionCount = (NUMBER_OF_COLUMNS div 2) + 1
# Compute the false positive threshold
let falsePositiveThreshold =
hypergeom_cdf(0, NUMBER_OF_COLUMNS, worstCaseConditionCount, samples_per_slot)
# Finally, compute the extended sample count
for i in samples_per_slot .. NUMBER_OF_COLUMNS:
if hypergeom_cdf(
allowed_failures,
NUMBER_OF_COLUMNS,
worstCaseConditionCount, i) <= falsePositiveThreshold:
return i
NUMBER_OF_COLUMNS
# https://github.com/ethereum/consensus-specs/blob/v1.5.0-alpha.6/specs/_features/eip7594/p2p-interface.md#verify_data_column_sidecar_inclusion_proof
proc verify_data_column_sidecar_inclusion_proof*(sidecar: DataColumnSidecar):
Result[void, cstring] =
## Verify if the given KZG Commitments are in included
## in the beacon block or not
let gindex =
KZG_COMMITMENTS_INCLUSION_PROOF_DEPTH_GINDEX.GeneralizedIndex
if not is_valid_merkle_branch(
hash_tree_root(sidecar.kzg_commitments),
sidecar.kzg_commitments_inclusion_proof,
KZG_COMMITMENTS_INCLUSION_PROOF_DEPTH.int,
get_subtree_index(gindex),
sidecar.signed_block_header.message.body_root):
return err("DataColumnSidecar: Inclusion proof is invalid")
ok()
# https://github.com/ethereum/consensus-specs/blob/v1.5.0-alpha.6/specs/_features/eip7594/p2p-interface.md#verify_data_column_sidecar_kzg_proofs
proc verify_data_column_sidecar_kzg_proofs*(sidecar: DataColumnSidecar):
Result[void, cstring] =
## Verify if the KZG Proofs consisting in the `DataColumnSidecar`
## is valid or not.
# Check if the data column sidecar index < NUMBER_OF_COLUMNS
if not (sidecar.index < NUMBER_OF_COLUMNS):
return err("Data column sidecar index exceeds the NUMBER_OF_COLUMNS")
# Check is the sidecar column length = sidecar.kzg_commitments length
# and sidecar.kzg_commitments length = sidecar.kzg_proofs length
if not (sidecar.column.len == sidecar.kzg_commitments.len):
return err("Data column sidecar length is not equal to the kzg_commitments length")
if not (sidecar.kzg_commitments.len == sidecar.kzg_proofs.len):
return err("Sidecar kzg_commitments length is not equal to the kzg_proofs length")
# Iterate through the cell indices
var cellIndices =
newSeq[CellIndex](MAX_BLOB_COMMITMENTS_PER_BLOCK)
for _ in 0..<sidecar.column.len:
cellIndices.add(sidecar.index * sidecar.column.lenu64)
let res =
verifyCellKzgProofBatch(sidecar.kzg_commitments.asSeq,
cellIndices,
sidecar.column.asSeq,
sidecar.kzg_proofs.asSeq)
if res.isErr():
return err("DataColumnSidecar: validation failed")
ok()
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