nimbus-eth2/beacon_chain/spec/crypto.nim

317 lines
11 KiB
Nim

# beacon_chain
# Copyright (c) 2018-2019 Status Research & Development GmbH
# Licensed and distributed under either of
# * MIT license (license terms in the root directory or at http://opensource.org/licenses/MIT).
# * Apache v2 license (license terms in the root directory or at http://www.apache.org/licenses/LICENSE-2.0).
# at your option. This file may not be copied, modified, or distributed except according to those terms.
# At the time of writing, the exact definitions of what should be used for
# cryptography in the spec is in flux, with sizes and test vectors still being
# hashed out. This layer helps isolate those chagnes.
# Useful conversation about BLS signatures (TODO: condense this)
#
# I can probably google this somehow, but bls signatures, anyone knows off the
# top of their head if they have to be combined one by one, or can two group
# signatures be combined? what happens to overlap then?
# Danny Ryan
# @djrtwo
# Dec 21 12:00
# Yeah, you can do any linear combination of signatures. but you have to
# remember the linear combination of pubkeys that constructed
# if you have two instances of a signature from pubkey p, then you need 2*p in
# the group pubkey
# because the attestation bitfield is only 1 bit per pubkey right now,
# attestations do not support this
# it could be extended to support N overlaps up to N times per pubkey if we
# had N bits per validator instead of 1
# We are shying away from this for the time being. If there end up being
# substantial difficulties in network layer aggregation, then adding bits
# to aid in supporting overlaps is one potential solution
# Jacek Sieka
# @arnetheduck
# Dec 21 12:02
# ah nice, you anticipated my followup question there :) so it's not a
# straight-off set union operation
# Danny Ryan
# @djrtwo
# Dec 21 12:02
# depending on the particular network level troubles we run into
# right
# aggregatng sigs and pubkeys are both just ec adds
# https://github.com/ethereum/py-evm/blob/d82b10ae361cde6abbac62f171fcea7809c4e3cf/eth/_utils/bls.py#L191-L202
# subtractions work too (i suppose this is obvious). You can linearly combine
# sigs or pubs in any way
import
sequtils,
stew/objects, hashes, nimcrypto/utils,
blscurve, json_serialization,
../version, digest
export
json_serialization
export
blscurve.init, blscurve.getBytes, blscurve.combine,
blscurve.`$`, blscurve.`==`,
blscurve.Signature
type
BlsValueType* = enum
Real
OpaqueBlob
BlsValue*[T] = object
# TODO This is a temporary type needed until we sort out the
# issues with invalid BLS values appearing in the SSZ test suites.
case kind*: BlsValueType
of Real:
blsValue*: T
of OpaqueBlob:
when T is blscurve.Signature:
blob*: array[96, byte]
else:
blob*: array[48, byte]
ValidatorPubKey* = BlsValue[blscurve.VerKey]
# ValidatorPubKey* = blscurve.VerKey
# ValidatorPubKey* = array[48, byte]
# The use of byte arrays proved to be a dead end pretty quickly.
# Plenty of code needs to be modified for a successful build and
# the changes will negatively affect the performance.
# ValidatorPrivKey* = BlsValue[blscurve.SigKey]
ValidatorPrivKey* = blscurve.SigKey
ValidatorSig* = BlsValue[blscurve.Signature]
BlsCurveType* = VerKey|SigKey|Signature
ValidatorPKI* = ValidatorPrivKey|ValidatorPubKey|ValidatorSig
proc init*[T](BLS: type BlsValue[T], val: auto): BLS =
result.kind = BlsValueType.Real
result.blsValue = init(T, val)
func `$`*(x: BlsValue): string =
if x.kind == Real:
$x.blsValue
else:
# r: is short for random. The prefix must be short
# due to the mechanics of the `shortLog` function.
"r:" & toHex(x.blob, true)
func `==`*(a, b: BlsValue): bool =
if a.kind != b.kind: return false
if a.kind == Real:
return a.blsValue == b.blsValue
else:
return a.blob == b.blob
func getBytes*(x: BlsValue): auto =
if x.kind == Real:
getBytes x.blsValue
else:
x.blob
func shortLog*(x: BlsValue): string =
($x)[0..7]
func shortLog*(x: BlsCurveType): string =
($x)[0..7]
proc hash*(x: BlsValue): Hash {.inline.} =
if x.kind == Real:
hash x.blsValue.getBytes()
else:
hash x.blob
template hash*(x: BlsCurveType): Hash =
hash(getBytes(x))
template `==`*[T](a: BlsValue[T], b: T): bool =
a.blsValue == b
template `==`*[T](a: T, b: BlsValue[T]): bool =
a == b.blsValue
func pubKey*(pk: ValidatorPrivKey): ValidatorPubKey =
when ValidatorPubKey is BlsValue:
ValidatorPubKey(kind: Real, blsValue: pk.getKey())
elif ValidatorPubKey is array:
pk.getKey.getBytes
else:
pk.getKey
proc combine*[T](a: openarray[BlsValue[T]]): T =
doAssert a.len > 0 and a[0].kind == Real
result = a[0].blsValue
for i in 1 ..< a.len:
doAssert a[i].kind == Real
result.combine a[i].blsValue
proc combine*[T](x: var BlsValue[T], other: BlsValue[T]) =
doAssert x.kind == Real and other.kind == Real
x.blsValue.combine(other.blsValue)
# https://github.com/ethereum/eth2.0-specs/blob/v0.8.3/specs/bls_signature.md#bls_aggregate_pubkeys
func bls_aggregate_pubkeys*(keys: openArray[ValidatorPubKey]): ValidatorPubKey =
var empty = true
for key in keys:
if empty:
result = key
empty = false
else:
result.combine(key)
# https://github.com/ethereum/eth2.0-specs/blob/v0.8.3/specs/bls_signature.md#bls_verify
func bls_verify*(
pubkey: ValidatorPubKey, msg: openArray[byte], sig: ValidatorSig,
domain: uint64): bool =
# name from spec!
when ValidatorPubKey is BlsValue:
if sig.kind != Real or pubkey.kind != Real:
# TODO: chronicles warning
return false
sig.blsValue.verify(msg, domain, pubkey.blsValue)
else:
sig.verify(msg, domain, pubkey)
# https://github.com/ethereum/eth2.0-specs/blob/v0.8.3/specs/bls_signature.md#bls_verify_multiple
func bls_verify_multiple*(
pubkeys: seq[ValidatorPubKey], message_hashes: openArray[Eth2Digest],
sig: ValidatorSig, domain: uint64): bool =
let L = len(pubkeys)
doAssert L == len(message_hashes)
if sig.kind != Real:
# TODO: chronicles warning
return false
# TODO optimize using multiPairing
for pubkey_message_hash in zip(pubkeys, message_hashes):
let (pubkey, message_hash) = pubkey_message_hash
doAssert pubkey.kind == Real
# TODO spec doesn't say to handle this specially, but it's silly to
# validate without any actual public keys.
if pubkey.blsValue != VerKey() and
not sig.blsValue.verify(message_hash.data, domain, pubkey.blsValue):
return false
true
when ValidatorPrivKey is BlsValue:
func bls_sign*(key: ValidatorPrivKey, msg: openarray[byte],
domain: uint64): ValidatorSig =
# name from spec!
if key.kind == Real:
ValidatorSig(kind: Real, blsValue: key.blsValue.sign(domain, msg))
else:
ValidatorSig(kind: OpaqueBlob)
else:
func bls_sign*(key: ValidatorPrivKey, msg: openarray[byte],
domain: uint64): ValidatorSig =
# name from spec!
ValidatorSig(kind: Real, blsValue: key.sign(domain, msg))
proc fromBytes*[T](R: type BlsValue[T], bytes: openarray[byte]): R =
# This is a workaround, so that we can deserialize the serialization of a
# default-initialized BlsValue without raising an exception
when defined(ssz_testing):
# Only for SSZ parsing tests, everything is an opaque blob
R(kind: OpaqueBlob, blob: toArray(result.blob.len, bytes))
else:
# Try if valid BLS value
let success = init(result.blsValue, bytes)
if not success:
# TODO: chronicles trace
result = R(kind: OpaqueBlob)
assert result.blob.len == bytes.len
result.blob[result.blob.low .. result.blob.high] = bytes
proc initFromBytes*[T](val: var BlsValue[T], bytes: openarray[byte]) =
val = fromBytes(BlsValue[T], bytes)
proc initFromBytes*(val: var BlsCurveType, bytes: openarray[byte]) =
val = init(type(val), bytes)
proc writeValue*(writer: var JsonWriter, value: ValidatorPubKey) {.inline.} =
when value is BlsValue:
doAssert value.kind == Real
writer.writeValue($value.blsValue)
else:
writer.writeValue($value)
proc readValue*(reader: var JsonReader, value: var ValidatorPubKey) {.inline.} =
value.initFromBytes(fromHex reader.readValue(string))
proc writeValue*(writer: var JsonWriter, value: ValidatorSig) {.inline.} =
when value is BlsValue:
if value.kind == Real:
writer.writeValue($value.blsValue)
else:
# Workaround: https://github.com/status-im/nim-beacon-chain/issues/374
let asHex = toHex(value.blob, true)
# echo "[Warning] writing raw opaque signature: ", asHex
writer.writeValue(asHex)
else:
writer.writeValue($value)
proc readValue*(reader: var JsonReader, value: var ValidatorSig) {.inline.} =
value.initFromBytes(fromHex reader.readValue(string))
proc writeValue*(writer: var JsonWriter, value: ValidatorPrivKey) {.inline.} =
when value is BlsValue:
doAssert value.kind == Real
writer.writeValue($value.blsValue)
else:
writer.writeValue($value)
proc readValue*(reader: var JsonReader, value: var ValidatorPrivKey) {.inline.} =
value.initFromBytes(fromHex reader.readValue(string))
when ValidatorPrivKey is BlsValue:
proc newPrivKey*(): ValidatorPrivKey =
ValidatorPrivKey(kind: Real, blsValue: SigKey.random())
else:
proc newPrivKey*(): ValidatorPrivKey =
SigKey.random()
when networkBackend == rlpxBackend:
import eth/rlp
when ValidatorPubKey is BlsValue:
proc append*(writer: var RlpWriter, value: ValidatorPubKey) =
writer.append if value.kind == Real: value.blsValue.getBytes()
else: value.blob
else:
proc append*(writer: var RlpWriter, value: ValidatorPubKey) =
writer.append value.getBytes()
proc read*(rlp: var Rlp, T: type ValidatorPubKey): T {.inline.} =
result.initFromBytes rlp.toBytes.toOpenArray
when ValidatorSig is BlsValue:
proc append*(writer: var RlpWriter, value: ValidatorSig) =
writer.append if value.kind == Real: value.blsValue.getBytes()
else: value.blob
else:
proc append*(writer: var RlpWriter, value: ValidatorSig) =
writer.append value.getBytes()
proc read*(rlp: var Rlp, T: type ValidatorSig): T {.inline.} =
result.initFromBytes rlp.toBytes.toOpenArray
proc writeValue*(writer: var JsonWriter, value: VerKey) {.inline.} =
writer.writeValue($value)
proc readValue*(reader: var JsonReader, value: var VerKey) {.inline.} =
value = VerKey.init(reader.readValue(string))
proc writeValue*(writer: var JsonWriter, value: Signature) {.inline.} =
writer.writeValue($value)
proc readValue*(reader: var JsonReader, value: var Signature) {.inline.} =
value = Signature.init(reader.readValue(string))