391 lines
14 KiB
Nim
391 lines
14 KiB
Nim
# beacon_chain
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# Copyright (c) 2018-2020 Status Research & Development GmbH
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# Licensed and distributed under either of
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# * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
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# * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
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# at your option. This file may not be copied, modified, or distributed except according to those terms.
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# At the time of writing, the exact definitions of what should be used for
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# cryptography in the spec is in flux, with sizes and test vectors still being
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# hashed out. This layer helps isolate those chagnes.
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# BLS signatures can be combined such that multiple signatures are aggregated.
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# Each time a new signature is added, the corresponding public key must be
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# added to the verification key as well - if a key signs twice, it must be added
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# twice to the verification key. Aggregated signatures can be combined
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# arbitrarily (like addition) as long as public keys are aggregated in the same
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# way.
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#
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# In eth2, we use a single bit to record which keys have signed, thus we cannot
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# combined overlapping aggregates - ie if we have an aggregate of signatures of
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# A, B and C, and another with B, C and D, we cannot practically combine them
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# even if in theory it is possible to allow this in BLS.
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{.push raises: [Defect].}
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import
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# Standard library
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options, tables,
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# Internal
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./digest,
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# Status
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stew/[endians2, objects, results, byteutils],
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blscurve,
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chronicles,
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json_serialization,
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# Standard library
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hashes
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export results, json_serialization
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# Type definitions
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# ----------------------------------------------------------------------
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const
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RawSigSize* = 96
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RawPubKeySize* = 48
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# RawPrivKeySize* = 48 for Miracl / 32 for BLST
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type
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BlsValueType* = enum
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Real
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OpaqueBlob
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BlsValue*[N: static int, T: blscurve.PublicKey or blscurve.Signature] = object
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# TODO This is a temporary type needed until we sort out the
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# issues with invalid BLS values appearing in the SSZ test suites.
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case kind*: BlsValueType
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of Real:
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blsValue*: T
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of OpaqueBlob:
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blob*: array[N, byte]
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ValidatorPubKey* = BlsValue[RawPubKeySize, blscurve.PublicKey]
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ValidatorPrivKey* = distinct blscurve.SecretKey
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ValidatorSig* = BlsValue[RawSigSize, blscurve.Signature]
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BlsCurveType* = ValidatorPrivKey | ValidatorPubKey | ValidatorSig
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BlsResult*[T] = Result[T, cstring]
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RandomSourceDepleted* = object of CatchableError
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TrustedSig* = object
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data*: array[RawSigSize, byte]
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SomeSig* = TrustedSig | ValidatorSig
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export AggregateSignature
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# API
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# ----------------------------------------------------------------------
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# https://github.com/ethereum/eth2.0-specs/blob/v0.12.3/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
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# Un-specced in either hash-to-curve or Eth2
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# TODO: Test suite should use `keyGen` instead
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ValidatorPubKey(kind: Real, blsValue: SecretKey(privkey).privToPub())
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proc toRealPubKey(pubkey: ValidatorPubKey): Option[ValidatorPubKey] =
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var validatorKeyCache {.threadvar.}:
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Table[array[RawPubKeySize, byte], Option[ValidatorPubKey]]
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case pubkey.kind:
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of Real:
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return some(pubkey)
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of OpaqueBlob:
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validatorKeyCache.withValue(pubkey.blob, key) do:
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return key[]
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do:
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var val: blscurve.PublicKey
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let maybeRealKey =
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if fromBytes(val, pubkey.blob):
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some ValidatorPubKey(kind: Real, blsValue: val)
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else:
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none ValidatorPubKey
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return validatorKeyCache.mGetOrPut(pubkey.blob, maybeRealKey)
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# TODO this needs a massive comment explaining the reasoning along with every
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# seemingly ad-hoc place where it's called - one shouldn't have to git-blame
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# commits and PRs for information which ought to be inplace here in the code
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proc initPubKey*(pubkey: ValidatorPubKey): ValidatorPubKey =
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let key = toRealPubKey(pubkey)
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if key.isNone:
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return ValidatorPubKey()
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key.get
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func init*(agg: var AggregateSignature, sig: ValidatorSig) {.inline.}=
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## Initializes an aggregate signature context
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## This assumes that the signature is valid
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agg.init(sig.blsValue)
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func aggregate*(agg: var AggregateSignature, sig: ValidatorSig) {.inline.}=
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## Aggregate two Validator Signatures
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## This assumes that they are real signatures
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agg.aggregate(sig.blsValue)
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func finish*(agg: AggregateSignature): ValidatorSig {.inline.}=
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## Canonicalize an AggregateSignature into a signature
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result.kind = Real
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result.blsValue.finish(agg)
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# https://github.com/ethereum/eth2.0-specs/blob/v0.12.3/specs/phase0/beacon-chain.md#bls-signatures
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proc blsVerify*(
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pubkey: ValidatorPubKey, message: openArray[byte],
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signature: ValidatorSig): bool =
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## Check that a signature is valid for a message
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## under the provided public key.
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## returns `true` if the signature is valid, `false` otherwise.
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##
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## The proof-of-possession MUST be verified before calling this function.
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## It is recommended to use the overload that accepts a proof-of-possession
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## to enforce correct usage.
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if signature.kind != Real:
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# Invalid signatures are possible in deposits (discussed with Danny)
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return false
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let realkey = toRealPubKey(pubkey)
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if realkey.isNone:
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# TODO: chronicles warning
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return false
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# TODO: remove fully if the comment below is not true anymore and
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# and we don't need this workaround
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# # TODO bls_verify_multiple(...) used to have this workaround, and now it
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# # lives here. No matter the signature, there's also no meaningful way to
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# # verify it -- it's a kind of vacuous truth. No pubkey/sig pairs. Sans a
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# # getBytes() or similar mechanism, pubKey == default(ValidatorPubKey) is
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# # a way to create many false positive matches. This seems odd.
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# if pubkey.getBytes() == default(ValidatorPubKey).getBytes():
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# return true
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realkey.get.blsValue.verify(message, signature.blsValue)
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func blsSign*(privkey: ValidatorPrivKey, message: openArray[byte]): ValidatorSig =
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## Computes a signature from a secret key and a message
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ValidatorSig(kind: Real, blsValue: SecretKey(privkey).sign(message))
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proc blsFastAggregateVerify*(
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publicKeys: openArray[ValidatorPubKey],
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message: openArray[byte],
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signature: ValidatorSig
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): bool =
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## Verify the aggregate of multiple signatures on the same message
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## This function is faster than AggregateVerify
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##
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## The proof-of-possession MUST be verified before calling this function.
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## It is recommended to use the overload that accepts a proof-of-possession
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## to enforce correct usage.
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# TODO: Note: `invalid` in the following paragraph means invalid by construction
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# The keys/signatures are not even points on the elliptic curves.
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# To respect both the IETF API and the fact that
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# we can have invalid public keys (as in not point on the elliptic curve),
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# requiring a wrapper indirection,
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# we need a first pass to extract keys from the wrapper
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# and then call fastAggregateVerify.
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# Instead:
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# - either we expose a new API: context + init-update-finish
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# in blscurve which already exists internally
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# - or at network/databases/serialization boundaries we do not
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# allow invalid BLS objects to pollute consensus routines
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if signature.kind != Real:
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return false
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var unwrapped: seq[PublicKey]
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for pubkey in publicKeys:
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let realkey = toRealPubKey(pubkey)
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if realkey.isNone:
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return false
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unwrapped.add realkey.get.blsValue
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fastAggregateVerify(unwrapped, message, signature.blsValue)
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proc toGaugeValue*(hash: Eth2Digest): int64 =
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# Only the last 8 bytes are taken into consideration in accordance
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# to the ETH2 metrics spec:
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# https://github.com/ethereum/eth2.0-metrics/blob/6a79914cb31f7d54858c7dd57eee75b6162ec737/metrics.md#interop-metrics
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cast[int64](uint64.fromBytesLE(hash.data.toOpenArray(24, 31)))
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# Codecs
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# ----------------------------------------------------------------------
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func `$`*(x: ValidatorPrivKey): string =
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"<private key>"
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func `$`*(x: BlsValue): string =
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# The prefix must be short
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# due to the mechanics of the `shortLog` function.
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case x.kind
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of Real: x.blsValue.toHex()
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of OpaqueBlob: "r:" & x.blob.toHex()
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func toRaw*(x: ValidatorPrivKey): array[32, byte] =
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# TODO: distinct type - see https://github.com/status-im/nim-blscurve/pull/67
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when BLS_BACKEND == BLST:
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result = SecretKey(x).exportRaw()
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else:
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# Miracl exports to 384-bit arrays, but Curve order is 256-bit
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let raw = SecretKey(x).exportRaw()
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result[0..32-1] = raw.toOpenArray(48-32, 48-1)
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func toRaw*(x: BlsValue): auto =
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if x.kind == Real:
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x.blsValue.exportRaw()
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else:
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x.blob
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func toRaw*(x: TrustedSig): auto =
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x.data
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func toHex*(x: BlsCurveType): string =
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toHex(toRaw(x))
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func fromRaw*(T: type ValidatorPrivKey, bytes: openArray[byte]): BlsResult[T] =
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var val: SecretKey
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if val.fromBytes(bytes):
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ok ValidatorPrivKey(val)
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else:
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err "bls: invalid private key"
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func fromRaw*[N, T](BT: type BlsValue[N, T], bytes: openArray[byte]): BlsResult[BT] =
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# This is a workaround, so that we can deserialize the serialization of a
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# default-initialized BlsValue without raising an exception
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when defined(ssz_testing) or BT is ValidatorPubKey:
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ok BT(kind: OpaqueBlob, blob: toArray(N, bytes))
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else:
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# Try if valid BLS value
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var val: T
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if fromBytes(val, bytes):
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ok BT(kind: Real, blsValue: val)
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else:
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ok BT(kind: OpaqueBlob, blob: toArray(N, bytes))
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func fromHex*(T: type BlsCurveType, hexStr: string): BlsResult[T] {.inline.} =
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## Initialize a BLSValue from its hex representation
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try:
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T.fromRaw(hexStr.hexToSeqByte())
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except ValueError:
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err "bls: cannot parse value"
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func `==`*(a, b: BlsValue): bool =
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# The assumption here is that converting to raw is mostly fast!
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case a.kind
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of Real:
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if a.kind == b.kind:
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a.blsValue == b.blsValue
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else:
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a.toRaw() == b.blob
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of OpaqueBlob:
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if a.kind == b.kind:
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a.blob == b.blob
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else:
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a.blob == b.toRaw()
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# Hashing
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# ----------------------------------------------------------------------
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template hash*(x: BlsCurveType): Hash =
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# TODO: prevent using secret keys
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bind toRaw
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hash(toRaw(x))
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# Serialization
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# ----------------------------------------------------------------------
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{.pragma: serializationRaises, raises: [SerializationError, IOError, Defect].}
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proc writeValue*(writer: var JsonWriter, value: ValidatorPubKey) {.
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inline, raises: [IOError, Defect].} =
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writer.writeValue(value.toHex())
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proc readValue*(reader: var JsonReader, value: var ValidatorPubKey)
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{.serializationRaises.} =
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let key = ValidatorPubKey.fromHex(reader.readValue(string))
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if key.isOk:
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value = key.get
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else:
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# TODO: Can we provide better diagnostic?
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raiseUnexpectedValue(reader, "Valid hex-encoded public key expected")
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proc writeValue*(writer: var JsonWriter, value: ValidatorSig) {.
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inline, raises: [IOError, Defect].} =
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# 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)
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{.serializationRaises.} =
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let sig = ValidatorSig.fromHex(reader.readValue(string))
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if sig.isOk:
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value = sig.get
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else:
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# TODO: Can we provide better diagnostic?
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raiseUnexpectedValue(reader, "Valid hex-encoded signature expected")
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proc writeValue*(writer: var JsonWriter, value: ValidatorPrivKey) {.
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inline, raises: [IOError, Defect].} =
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writer.writeValue(value.toHex())
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proc readValue*(reader: var JsonReader, value: var ValidatorPrivKey)
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{.serializationRaises.} =
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let key = ValidatorPrivKey.fromHex(reader.readValue(string))
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if key.isOk:
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value = key.get
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else:
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# TODO: Can we provide better diagnostic?
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raiseUnexpectedValue(reader, "Valid hex-encoded private key expected")
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template fromSszBytes*(T: type BlsValue, bytes: openArray[byte]): auto =
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let v = fromRaw(T, bytes)
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if v.isErr:
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raise newException(MalformedSszError, $v.error)
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v[]
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# Logging
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# ----------------------------------------------------------------------
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func shortLog*(x: BlsValue): string =
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## Logging for wrapped BLS types
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## that may contain valid or non-validated data
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# The prefix must be short
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# due to the mechanics of the `shortLog` function.
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if x.kind == Real:
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x.blsValue.exportRaw().toOpenArray(0, 3).toHex()
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else:
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"r:" & x.blob.toOpenArray(0, 3).toHex()
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func shortLog*(x: ValidatorPrivKey): string =
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## Logging for raw unwrapped BLS types
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"<private key>"
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func shortLog*(x: TrustedSig): string =
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x.data.toOpenArray(0, 3).toHex()
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# Initialization
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# ----------------------------------------------------------------------
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# TODO more specific exceptions? don't raise?
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# For confutils
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func init*(T: typedesc[ValidatorPrivKey], hex: string): T {.noInit, raises: [ValueError, Defect].} =
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let v = T.fromHex(hex)
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if v.isErr:
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raise (ref ValueError)(msg: $v.error)
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v[]
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# For mainchain monitor
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func init*(T: typedesc[ValidatorPubKey], data: array[RawPubKeySize, byte]): T {.noInit, raises: [ValueError, Defect].} =
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let v = T.fromRaw(data)
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if v.isErr:
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raise (ref ValueError)(msg: $v.error)
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v[]
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# For mainchain monitor
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func init*(T: typedesc[ValidatorSig], data: array[RawSigSize, byte]): T {.noInit, raises: [ValueError, Defect].} =
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let v = T.fromRaw(data)
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if v.isErr:
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raise (ref ValueError)(msg: $v.error)
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v[]
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proc burnMem*(key: var ValidatorPrivKey) =
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key = default(ValidatorPrivKey)
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