create file for common signature ops, derivePubkey for ECDSA & BLS

Also cleans up the imports of the ECDSA file and adds the copyright header

constantine/signatures/bls_signatures.nim

@@ -15,7 +15,10 @@ import
     constantine/named/algebras,
     constantine/hash_to_curve/[hash_to_curve, h2c_hash_to_field],
     constantine/hashes,
-    constantine/platforms/views
+    constantine/platforms/views,
+    constantine/signatures/common_signature_ops # for `derivePubkey`
+
+export common_signature_ops
 
 # ############################################################
 #
@@ -34,20 +37,6 @@ import
 {.push raises: [].} # No exceptions allowed in core cryptographic operations
 {.push checks: off.} # No defects due to array bound checking or signed integer overflow allowed
 
-func derivePubkey*[Pubkey, SecKey](pubkey: var Pubkey, seckey: SecKey) =
-  ## Generates the public key associated with the input secret key.
-  ##
-  ## The secret key MUST be in range (0, curve order)
-  ## 0 is INVALID
-  const Group = Pubkey.G
-  type Field = Pubkey.F
-  const EC = Field.Name
-
-  var pk {.noInit.}: EC_ShortW_Jac[Field, Group]
-  pk.setGenerator()
-  pk.scalarMul(seckey)
-  pubkey.affine(pk)
-
 func coreSign*[Sig, SecKey](
     signature: var Sig,
     secretKey: SecKey,

constantine/signatures/common_signature_ops.nim

@@ -0,0 +1,26 @@
+# Constantine
+# Copyright (c) 2018-2019    Status Research & Development GmbH
+# Copyright (c) 2020-Present Mamy André-Ratsimbazafy
+# 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.
+
+import
+    constantine/math/[ec_shortweierstrass],
+    constantine/named/zoo_generators,
+    constantine/named/algebras
+
+func derivePubkey*[Pubkey, SecKey](pubkey: var Pubkey, seckey: SecKey) =
+  ## Generates the public key associated with the input secret key.
+  ##
+  ## The secret key MUST be in range (0, curve order)
+  ## 0 is INVALID
+  const Group = Pubkey.G
+  type Field = Pubkey.F
+  const EC = Field.Name
+
+  var pk {.noInit.}: EC_ShortW_Jac[Field, Group]
+  pk.setGenerator()
+  pk.scalarMul(seckey)
+  pubkey.affine(pk)

constantine/signatures/ecdsa.nim

@@ -1,17 +1,28 @@
+# Constantine
+# Copyright (c) 2018-2019    Status Research & Development GmbH
+# Copyright (c) 2020-Present Mamy André-Ratsimbazafy
+# 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.
+
 import
-  ../hashes,
-  ../named/algebras,
-  ../math/io/[io_bigints, io_fields, io_ec],
-  ../math/elliptic/[ec_shortweierstrass_affine, ec_shortweierstrass_jacobian, ec_scalar_mul, ec_multi_scalar_mul],
-  ../math/[arithmetic, ec_shortweierstrass],
-  ../platforms/[abstractions, views],
-  ../serialization/codecs, # for fromHex and (in the future) base64 encoding
-  ../mac/mac_hmac, # for deterministic nonce generation via RFC 6979
-  ../named/zoo_generators, # for generator
-  ../csprngs/sysrand
+  constantine/hashes,
+  constantine/named/algebras,
+  constantine/math/io/[io_bigints, io_fields, io_ec],
+  constantine/math/elliptic/[ec_shortweierstrass_affine, ec_shortweierstrass_jacobian, ec_scalar_mul, ec_multi_scalar_mul],
+  constantine/math/[arithmetic, ec_shortweierstrass],
+  constantine/platforms/[abstractions, views],
+  constantine/serialization/codecs, # for fromHex and (in the future) base64 encoding
+  constantine/mac/mac_hmac, # for deterministic nonce generation via RFC 6979
+  constantine/named/zoo_generators, # for generator
+  constantine/csprngs/sysrand,
+  constantine/signatures/common_signature_ops # for `derivePubkey`
 
 import std / macros # for `update` convenience helper
 
+export common_signature_ops
+
 type
   ## Decides the type of sampler we use for the nonce. By default
   ## a simple uniform random sampler. Alternatively a deterministic