nimbus-eth2/beacon_chain/spec/crypto.nim

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# beacon_chain
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# Copyright (c) 2018-2020 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.
# 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.
# BLS signatures can be combined such that multiple signatures are aggregated.
# Each time a new signature is added, the corresponding public key must be
# added to the verification key as well - if a key signs twice, it must be added
# twice to the verification key. Aggregated signatures can be combined
# arbitrarily (like addition) as long as public keys are aggregated in the same
# way.
#
# In eth2, we use a single bit to record which keys have signed, thus we cannot
# combined overlapping aggregates - ie if we have an aggregate of signatures of
# A, B and C, and another with B, C and D, we cannot practically combine them
# even if in theory it is possible to allow this in BLS.
{.push raises: [Defect].}
import
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# Internal
./digest, ../ssz/types,
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# Status
stew/[endians2, objects, results, byteutils],
nimcrypto/sysrand,
blscurve,
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chronicles,
json_serialization,
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# Standard library
hashes
export results, json_serialization
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# Type definitions
# ----------------------------------------------------------------------
const
RawSigSize* = 96
RawPubKeySize* = 48
RawPrivKeySize* = 48
type
BlsValueType* = enum
Real
OpaqueBlob
BlsValue*[N: static int, 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:
blob*: array[N, byte]
ValidatorPubKey* = BlsValue[RawPubKeySize, blscurve.PublicKey]
ValidatorPrivKey* = distinct blscurve.SecretKey
ValidatorSig* = BlsValue[RawSigSize, blscurve.Signature]
BlsCurveType* = ValidatorPrivKey | ValidatorPubKey | ValidatorSig
BlsResult*[T] = Result[T, cstring]
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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
template `==`*[N, T](a: BlsValue[N, T], b: T): bool =
a.blsValue == b
template `==`*[N, T](a: T, b: BlsValue[N, T]): bool =
a == b.blsValue
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# API
# ----------------------------------------------------------------------
# https://github.com/ethereum/eth2.0-specs/blob/v0.11.3/specs/phase0/beacon-chain.md#bls-signatures
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func toPubKey*(privkey: ValidatorPrivKey): ValidatorPubKey =
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## Create a private key from a public key
# Un-specced in either hash-to-curve or Eth2
# TODO: Test suite should use `keyGen` instead
when ValidatorPubKey is BlsValue:
ValidatorPubKey(kind: Real, blsValue: SecretKey(privkey).privToPub())
elif ValidatorPubKey is array:
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privkey.getKey.getBytes
else:
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privkey.getKey
# https://github.com/ethereum/eth2.0-specs/blob/v0.11.3/specs/phase0/beacon-chain.md#bls-signatures
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func aggregate*[T](values: openarray[ValidatorSig]): ValidatorSig =
## Aggregate arrays of sequences of Validator Signatures
## This assumes that they are real signatures
result = BlsValue[T](kind: Real, blsValue: values[0].BlsValue)
for i in 1 ..< values.len:
result.blsValue.aggregate(values[i].blsValue)
func aggregate*(x: var ValidatorSig, other: ValidatorSig) =
## Aggregate 2 Validator Signatures
## This assumes that they are real signatures
x.blsValue.aggregate(other.blsValue)
# https://github.com/ethereum/eth2.0-specs/blob/v0.11.3/specs/phase0/beacon-chain.md#bls-signatures
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func blsVerify*(
pubkey: ValidatorPubKey, message: openArray[byte],
signature: ValidatorSig): bool =
## Check that a signature is valid for a message
## under the provided public key.
## returns `true` if the signature is valid, `false` otherwise.
##
## The proof-of-possession MUST be verified before calling this function.
## It is recommended to use the overload that accepts a proof-of-possession
## to enforce correct usage.
if signature.kind != Real:
# Invalid signatures are possible in deposits (discussed with Danny)
return false
if pubkey.kind != Real:
# TODO: chronicles warning
return false
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# TODO: remove fully if the comment below is not true anymore and
# and we don't need this workaround
# # TODO bls_verify_multiple(...) used to have this workaround, and now it
# # lives here. No matter the signature, there's also no meaningful way to
# # verify it -- it's a kind of vacuous truth. No pubkey/sig pairs. Sans a
# # getBytes() or similar mechanism, pubKey == default(ValidatorPubKey) is
# # a way to create many false positive matches. This seems odd.
# if pubkey.getBytes() == default(ValidatorPubKey).getBytes():
# return true
pubkey.blsValue.verify(message, signature.blsValue)
func blsSign*(privkey: ValidatorPrivKey, message: openarray[byte]): ValidatorSig =
## Computes a signature from a secret key and a message
ValidatorSig(kind: Real, blsValue: SecretKey(privkey).sign(message))
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func blsFastAggregateVerify*[T: byte|char](
publicKeys: openarray[ValidatorPubKey],
message: openarray[T],
signature: ValidatorSig
): bool =
## Verify the aggregate of multiple signatures on the same message
## This function is faster than AggregateVerify
##
## The proof-of-possession MUST be verified before calling this function.
## It is recommended to use the overload that accepts a proof-of-possession
## to enforce correct usage.
# TODO: Note: `invalid` in the following paragraph means invalid by construction
# The keys/signatures are not even points on the elliptic curves.
# To respect both the IETF API and the fact that
# we can have invalid public keys (as in not point on the elliptic curve),
# requiring a wrapper indirection,
# we need a first pass to extract keys from the wrapper
# and then call fastAggregateVerify.
# Instead:
# - either we expose a new API: context + init-update-finish
# in blscurve which already exists internally
# - or at network/databases/serialization boundaries we do not
# allow invalid BLS objects to pollute consensus routines
if signature.kind != Real:
return false
var unwrapped: seq[PublicKey]
for pubkey in publicKeys:
if pubkey.kind != Real:
return false
unwrapped.add pubkey.blsValue
return fastAggregateVerify(unwrapped, message, signature.blsValue)
proc newKeyPair*(): BlsResult[tuple[pub: ValidatorPubKey, priv: ValidatorPrivKey]] =
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## Generates a new public-private keypair
## This requires entropy on the system
# The input-keying-material requires 32 bytes at least for security
# The generation is deterministic and the input-keying-material
# must be protected against side-channel attacks
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var ikm: array[32, byte]
if randomBytes(ikm) != 32:
return err "bls: no random bytes"
var
sk: SecretKey
pk: PublicKey
if keyGen(ikm, pk, sk):
ok((ValidatorPubKey(kind: Real, blsValue: pk), ValidatorPrivKey(sk)))
else:
err "bls: cannot generate keypair"
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proc toGaugeValue*(hash: Eth2Digest): int64 =
# Only the last 8 bytes are taken into consideration in accordance
# to the ETH2 metrics spec:
# https://github.com/ethereum/eth2.0-metrics/blob/6a79914cb31f7d54858c7dd57eee75b6162ec737/metrics.md#interop-metrics
cast[int64](uint64.fromBytesLE(hash.data[24..31]))
# Codecs
# ----------------------------------------------------------------------
func `$`*(x: ValidatorPrivKey): string =
"<private key>"
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func `$`*(x: BlsValue): string =
# The prefix must be short
# due to the mechanics of the `shortLog` function.
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if x.kind == Real:
x.blsValue.toHex()
else:
"raw: " & x.blob.toHex()
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func toRaw*(x: ValidatorPrivKey): array[RawPrivKeySize, byte] =
SecretKey(x).exportRaw()
func toRaw*(x: BlsValue): auto =
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if x.kind == Real:
x.blsValue.exportRaw()
else:
x.blob
func toHex*(x: BlsCurveType): string =
toHex(toRaw(x))
func fromRaw*(T: type ValidatorPrivKey, bytes: openarray[byte]): BlsResult[T] =
var val: SecretKey
if val.fromBytes(bytes):
ok ValidatorPrivKey(val)
else:
err "bls: invalid private key"
func fromRaw*[N, T](BT: type BlsValue[N, T], bytes: openarray[byte]): BlsResult[BT] =
# 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
ok BT(kind: OpaqueBlob, blob: toArray(N, bytes))
else:
# Try if valid BLS value
var val: T
if fromBytes(val, bytes):
ok BT(kind: Real, blsValue: val)
else:
ok BT(kind: OpaqueBlob, blob: toArray(N, bytes))
func fromHex*(T: type BlsCurveType, hexStr: string): BlsResult[T] {.inline.} =
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## Initialize a BLSValue from its hex representation
try:
T.fromRaw(hexStr.hexToSeqByte())
except ValueError:
err "bls: cannot parse value"
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# Hashing
# ----------------------------------------------------------------------
template hash*(x: BlsCurveType): Hash =
# TODO: prevent using secret keys
bind toRaw
hash(toRaw(x))
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# Serialization
# ----------------------------------------------------------------------
proc writeValue*(writer: var JsonWriter, value: ValidatorPubKey) {.
inline, raises: [IOError, Defect].} =
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writer.writeValue(value.toHex())
proc readValue*(reader: var JsonReader, value: var ValidatorPubKey) {.
inline, raises: [Exception].} =
value = ValidatorPubKey.fromHex(reader.readValue(string)).tryGet()
proc writeValue*(writer: var JsonWriter, value: ValidatorSig) {.
inline, raises: [IOError, Defect].} =
# Workaround: https://github.com/status-im/nim-beacon-chain/issues/374
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writer.writeValue(value.toHex())
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proc readValue*(reader: var JsonReader, value: var ValidatorSig) {.
inline, raises: [Exception].} =
value = ValidatorSig.fromHex(reader.readValue(string)).tryGet()
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proc writeValue*(writer: var JsonWriter, value: ValidatorPrivKey) {.
inline, raises: [IOError, Defect].} =
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writer.writeValue(value.toHex())
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proc readValue*(reader: var JsonReader, value: var ValidatorPrivKey) {.
inline, raises: [Exception].} =
value = ValidatorPrivKey.fromHex(reader.readValue(string)).tryGet()
template fromSszBytes*(T: type BlsValue, bytes: openarray[byte]): auto =
let v = fromRaw(T, bytes)
if v.isErr:
raise newException(MalformedSszError, $v.error)
v[]
# Logging
# ----------------------------------------------------------------------
func shortLog*(x: BlsValue): string =
## Logging for wrapped BLS types
## that may contain valid or non-validated data
# The prefix must be short
# due to the mechanics of the `shortLog` function.
if x.kind == Real:
x.blsValue.exportRaw()[0..3].toHex()
else:
"raw: " & x.blob[0..3].toHex()
func shortLog*(x: ValidatorPrivKey): string =
## Logging for raw unwrapped BLS types
x.toRaw()[0..3].toHex()
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# Initialization
# ----------------------------------------------------------------------
# TODO more specific exceptions? don't raise?
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# For confutils
func init*(T: typedesc[ValidatorPrivKey], hex: string): T {.noInit, raises: [ValueError, Defect].} =
let v = T.fromHex(hex)
if v.isErr:
raise (ref ValueError)(msg: $v.error)
return v[]
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# For mainchain monitor
func init*(T: typedesc[ValidatorPubKey], data: array[RawPubKeySize, byte]): T {.noInit, raises: [ValueError, Defect].} =
let v = T.fromRaw(data)
if v.isErr:
raise (ref ValueError)(msg: $v.error)
return v[]
# For mainchain monitor
func init*(T: typedesc[ValidatorSig], data: array[RawSigSize, byte]): T {.noInit, raises: [ValueError, Defect].} =
let v = T.fromRaw(data)
if v.isErr:
raise (ref ValueError)(msg: $v.error)
return v[]