Consolidate internal backend API and implement #90 (#100)

* Consolidate internal backend API and implement #90

* fix a missing ContextCoreAggregateVerify DST

* Remove parallel batch verification mention from this refactoring

* Delete the refactored files

blscurve.nim

@@ -7,9 +7,9 @@
 # This file may not be copied, modified, or distributed except according to
 # those terms.
 
-const BLS_ETH2_SPEC* = "v1.0.0-rc0"
+const BLS_ETH2_SPEC* = "v1.0.0"
 import
-  blscurve/bls_backend,
+  blscurve/bls_public_exports,
   blscurve/keygen_eip2333
 
-export bls_backend, keygen_eip2333
+export bls_public_exports, keygen_eip2333

blscurve/bls_backend.nim

@@ -45,16 +45,8 @@ else:
   const BLS_BACKEND* = Miracl
 
 when BLS_BACKEND == BLST:
-  import ./blst/bls_sig_min_pubkey_size_pop, ./blst/sha256_abi
-  export bls_sig_min_pubkey_size_pop, sha256_abi
+  import ./blst/blst_min_pubkey_sig_core
+  export blst_min_pubkey_sig_core
 else:
-  import
-    ./miracl/bls_signature_scheme
-  export
-    SecretKey, PublicKey, Signature, ProofOfPossession,
-    AggregateSignature,
-    `==`,
-    init, aggregate, finish, aggregateAll,
-    sign, verify, aggregateVerify, fastAggregateVerify,
-    publicFromSecret, isZero,
-    fromHex, fromBytes, toHex, serialize, exportRaw
+  import ./miracl/miracl_min_pubkey_sig_core
+  export miracl_min_pubkey_sig_core

blscurve/bls_public_exports.nim

@@ -0,0 +1,29 @@
+# Nim-BLSCurve
+# Copyright (c) 2018-Present Status Research & Development GmbH
+# Licensed under either of
+#  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
+#  * MIT license ([LICENSE-MIT](LICENSE-MIT))
+# at your option.
+# This file may not be copied, modified, or distributed except according to
+# those terms.
+
+import bls_backend
+
+export
+  BLS_BACKEND, BlsBackendKind,
+  SecretKey, PublicKey, Signature, ProofOfPossession,
+  AggregateSignature, AggregatePublicKey,
+  `==`,
+  init, aggregate, finish, aggregateAll,
+  publicFromSecret,
+  fromHex, fromBytes, toHex, serialize, exportRaw
+
+import bls_sig_min_pubkey
+
+export
+  sign,
+  verify, aggregateVerify, fastAggregateVerify
+
+when BLS_BACKEND == BLST:
+  import ./blst/sha256_abi
+  export sha256_abi

blscurve/bls_sig_min_pubkey.nim

@@ -0,0 +1,253 @@
+# Nim-BLST
+# Copyright (c) 2020 Status Research & Development GmbH
+# Licensed under either of
+#  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
+#  * MIT license ([LICENSE-MIT](LICENSE-MIT))
+# at your option.
+# This file may not be copied, modified, or distributed except according to
+# those terms.
+
+import bls_backend
+
+# Public API
+# ----------------------------------------------------------------------
+#
+# There are 3 BLS schemes that differ in handling rogue key attacks
+# - basic: requires message signed by an aggregate signature to be distinct
+# - message augmentation: signatures are generated over the concatenation of public key and the message
+#                         enforcing message signed by different public key to be distinct
+# - proof of possession: a separate public key called proof-of-possession is used to allow signing
+#                        on the same message while defending against rogue key attacks
+# with respective ID / domain separation tag:
+# - BLS_SIG_BLS12381G2-SHA256-SSWU-RO-_NUL_
+# - BLS_SIG_BLS12381G2-SHA256-SSWU-RO-_AUG_
+# - BLS_SIG_BLS12381G2-SHA256-SSWU-RO-_POP_
+#   - POP tag: BLS_POP_BLS12381G2-SHA256-SSWU-RO-_POP_
+#
+# We implement the proof-of-possession scheme
+# Compared to the spec API are modified
+# to enforce usage of the proof-of-posession (as recommended)
+
+const DST = "BLS_SIG_BLS12381G2_XMD:SHA-256_SSWU_RO_POP_"
+const DST_POP = "BLS_POP_BLS12381G2_XMD:SHA-256_SSWU_RO_POP_"
+
+func popProve*(secretKey: SecretKey, publicKey: PublicKey): ProofOfPossession =
+  ## Generate a proof of possession for the public/secret keypair
+  # 1. xP = SK * P
+  # 2. PK = point_to_pubkey(xP)
+  # 3. Q = hash_pubkey_to_point(PK)
+  # 4. R = SK * Q
+  # 5. proof = point_to_signature(R)
+  # 6. return proof
+  var pk{.noInit.}: array[48, byte]
+  pk.rawFromPublic(publicKey) # 2. Convert to raw bytes compressed form
+  result.coreSign(secretKey, pk, DST_POP)     # 3-4. hash_to_curve and multiply by secret key
+
+func popProve*(secretKey: SecretKey): ProofOfPossession =
+  ## Generate a proof of possession for the public key associated with the input secret key
+  ## Note: this internally recomputes the public key, an overload that doesn't is available.
+  # 1. xP = SK * P
+  # 2. PK = point_to_pubkey(xP)
+  # 3. Q = hash_pubkey_to_point(PK)
+  # 4. R = SK * Q
+  # 5. proof = point_to_signature(R)
+  # 6. return proof
+  var pubkey {.noInit.}: PublicKey
+  let ok {.used.} = pubkey.publicFromSecret(secretKey)
+  assert ok, "The secret key is INVALID, it should be initialized non-zero with keyGen or derive_child_secretKey"
+  result = popProve(secretKey, pubkey)
+
+func popVerify*(publicKey: PublicKey, proof: ProofOfPossession): bool =
+  ## Verify if the proof-of-possession is valid for the public key
+  ## returns true if valid or false if invalid
+  # 1. R = signature_to_point(proof)
+  # 2. If R is INVALID, return INVALID
+  # 3. If signature_subgroup_check(R) is INVALID, return INVALID
+  # 4. If KeyValidate(PK) is INVALID, return INVALID
+  # 5. xP = pubkey_to_point(PK)
+  # 6. Q = hash_pubkey_to_point(PK)
+  # 7. C1 = pairing(Q, xP)
+  # 8. C2 = pairing(R, P)
+  # 9. If C1 == C2, return VALID, else return INVALID
+  var pk{.noInit.}: array[48, byte]
+  pk.rawFromPublic(publicKey)
+  result = coreVerifyNoGroupCheck(publicKey, pk, proof, DST_POP)
+
+func sign*[T: byte|char](secretKey: SecretKey, message: openarray[T]): Signature =
+  ## Computes a signature
+  ## from a secret key and a message
+  ##
+  ## The SecretKey MUST be directly created via
+  ## `keyGen` or `derive_child_secretKey`
+  ## or deserialized from `fromBytes` or `fromHex`.
+  ## This ensures the precondition that it's not a zero key.
+  result.coreSign(secretKey, message, DST)
+
+func verify*[T: byte|char](
+       publicKey: PublicKey,
+       proof: ProofOfPossession,
+       message: openarray[T],
+       signature: Signature) : 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.
+  ##
+  ## The PublicKey MUST be directly created via
+  ## `publicFromPrivate`
+  ## or deserialized from `fromBytes` or `fromHex`.
+  ## This ensures the precondition that it's not a zero key
+  ## and that is has been subgroup checked
+  if not publicKey.popVerify(proof):
+    return false
+  return publicKey.coreVerifyNoGroupCheck(message, signature, DST)
+
+func verify*[T: byte|char](
+       publicKey: PublicKey,
+       message: openarray[T],
+       signature: Signature) : 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.
+  ##
+  ## The PublicKey MUST be directly created via
+  ## `publicFromPrivate`
+  ## or deserialized from `fromBytes` or `fromHex`.
+  ## This ensures the precondition that it's not a zero key
+  ## and that is has been subgroup checked
+  return publicKey.coreVerifyNoGroupCheck(message, signature, DST)
+
+func aggregateVerify*(
+        publicKeys: openarray[PublicKey],
+        proofs: openarray[ProofOfPossession],
+        messages: openarray[string or seq[byte]],
+        signature: Signature): bool {.noInline.} =
+  ## Check that an aggregated signature over several (publickey, message) pairs
+  ## returns `true` if the signature is valid, `false` otherwise.
+  ##
+  ## Compared to the IETF spec API, it is modified to
+  ## enforce proper usage of the proof-of-possessions
+  # Note: we can't have openarray of openarrays until openarrays are first-class value types
+  if publicKeys.len != proofs.len or publicKeys != messages.len:
+    return false
+  if not(publicKeys.len >= 1):
+    return false
+
+  var ctx{.noInit.}: ContextCoreAggregateVerify[DST]
+
+  ctx.init()
+  for i in 0 ..< publicKeys.len:
+    if not publicKeys[i].popVerify(proofs[i]):
+      return false
+    if not ctx.update(publicKeys[i], messages[i]):
+      return false
+  return ctx.finish(signature)
+
+func aggregateVerify*(
+        publicKeys: openarray[PublicKey],
+        messages: openarray[string or seq[byte]],
+        signature: Signature): bool =
+  ## Check that an aggregated signature over several (publickey, message) pairs
+  ## 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.
+  # Note: we can't have openarray of openarrays until openarrays are first-class value types
+  if publicKeys.len != messages.len:
+    return false
+  if not(publicKeys.len >= 1):
+    return false
+
+  var ctx{.noInit.}: ContextCoreAggregateVerify[DST]
+
+  ctx.init()
+  for i in 0 ..< publicKeys.len:
+    if not ctx.update(publicKeys[i], messages[i]):
+      return false
+  return ctx.finish(signature)
+
+func aggregateVerify*[T: string or seq[byte]](
+        publicKey_msg_pairs: openarray[tuple[publicKey: PublicKey, message: T]],
+        signature: Signature): bool =
+  ## Check that an aggregated signature over several (publickey, message) pairs
+  ## 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.
+  # Note: we can't have tuple of openarrays until openarrays are first-class value types
+  if not(publicKey_msg_pairs.len >= 1):
+    return false
+
+  var ctx{.noInit.}: ContextCoreAggregateVerify[DST]
+
+  ctx.init()
+  for i in 0 ..< publicKey_msg_pairs.len:
+    if not ctx.update(publicKey_msg_pairs[i].publicKey, publicKey_msg_pairs[i].message):
+      return false
+  return ctx.finish(signature)
+
+func fastAggregateVerify*[T: byte|char](
+        publicKeys: openarray[PublicKey],
+        proofs: openarray[ProofOfPossession],
+        message: openarray[T],
+        signature: Signature
+      ): bool =
+  ## Verify the aggregate of multiple signatures on the same message
+  ## This function is faster than AggregateVerify
+  ## Compared to the IETF spec API, it is modified to
+  ## enforce proper usage of the proof-of-posession
+  # 1. aggregate = pubkey_to_point(PK_1)
+  # 2. for i in 2, ..., n:
+  # 3.     next = pubkey_to_point(PK_i)
+  # 4.     aggregate = aggregate + next
+  # 5. PK = point_to_pubkey(aggregate)
+  # 6. return CoreVerify(PK, message, signature)
+  if publicKeys.len == 0:
+    return false
+  if not publicKeys[0].popVerify(proofs[0]):
+    return false
+  var aggPK {.noInit.}: AggregatePublicKey
+  aggPK.init(publicKeys[0])
+  for i in 1 ..< publicKeys.len:
+    if not publicKeys[i].popVerify(proofs[i]):
+      return false
+    # We assume that the PublicKey is in on curve, in the proper subgroup
+    aggPK.aggregate(publicKeys[i])
+
+  var aggAffine{.noInit.}: PublicKey
+  aggAffine.finish(aggAffine)
+  return coreVerifyNoGroupCheck(aggAffine, message, signature, DST)
+
+func fastAggregateVerify*[T: byte|char](
+        publicKeys: openarray[PublicKey],
+        message: openarray[T],
+        signature: Signature
+      ): 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.
+  # 1. aggregate = pubkey_to_point(PK_1)
+  # 2. for i in 2, ..., n:
+  # 3.     next = pubkey_to_point(PK_i)
+  # 4.     aggregate = aggregate + next
+  # 5. PK = point_to_pubkey(aggregate)
+  # 6. return CoreVerify(PK, message, signature)
+  if publicKeys.len == 0:
+    return false
+
+  var aggAffine{.noInit.}: PublicKey
+  if not aggAffine.aggregateAll(publicKeys):
+    return false
+  return coreVerifyNoGroupCheck(aggAffine, message, signature, DST)