From 27211311682d6c28d7ca089f6a604cab2efd4612 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mamy=20Andr=C3=A9-Ratsimbazafy?= <mamy_github@numforge.co>
Date: Sun, 27 Sep 2020 17:55:31 +0200
Subject: [PATCH] Move curve specific square root

---
 .../arithmetic/finite_fields_square_root.nim  | 24 ++++---------------
 constantine/curves/addchain_square_roots.nim  | 17 +++++++++++++
 constantine/curves/bls12_377_square_root.nim  | 20 ++++++++++++++++
 3 files changed, 42 insertions(+), 19 deletions(-)
 create mode 100644 constantine/curves/addchain_square_roots.nim
 create mode 100644 constantine/curves/bls12_377_square_root.nim

diff --git a/constantine/arithmetic/finite_fields_square_root.nim b/constantine/arithmetic/finite_fields_square_root.nim
index 24d07e2..588270d 100644
--- a/constantine/arithmetic/finite_fields_square_root.nim
+++ b/constantine/arithmetic/finite_fields_square_root.nim
@@ -7,9 +7,9 @@
 # at your option. This file may not be copied, modified, or distributed except according to those terms.
 
 import
-  std/macros,
   ../primitives,
   ../config/[common, type_fp, curves],
+  ../curves/addchain_square_roots,
   ../io/[io_bigints, io_fields],
   ./bigints, ./finite_fields, ./limbs_montgomery
 
@@ -112,25 +112,11 @@ func sqrt_if_square_p3mod4[C](a: var Fp[C]): SecretBool {.inline.} =
 # Tonelli Shanks for any prime
 # ------------------------------------------------------------
 
-const
-  # with e = 2adicity
-  # p == s * 2^e + 1
-  # root_of_unity = smallest_quadratic_nonresidue^s
-  # exponent = (p-1-2^e)/2^e / 2
-  TonelliShanks_exponent_BLS12_377 = BigInt[330].fromHex"0x35c748c2f8a21d58c760b80d94292763445b3e601ea271e3de6c45f741290002e16ba88600000010a11"
-  TonelliShanks_twoAdicity_BLS12_377 = 46
-  TonelliShanks_root_of_unity_BLS12_377 = Fp[BLS12_377].fromHex"0x382d3d99cdbc5d8fe9dee6aa914b0ad14fcaca7022110ec6eaa2bc56228ac41ea03d28cc795186ba6b5ef26b00bbe8"
-
-{.experimental: "dynamicBindSym".}
-
-macro tsGet(C: static Curve, value: untyped): untyped =
-  return bindSym("TonelliShanks_" & $value & "_" & $C)
-
 func precompute_tonelli_shanks[C](
        a_pre_exp: var Fp[C],
        a: Fp[C]) =
   a_pre_exp = a
-  a_pre_exp.powUnsafeExponent(C.tsGet(exponent))
+  a_pre_exp.powUnsafeExponent(C.tonelliShanks(exponent))
 
 func isSquare_tonelli_shanks[C](
        a, a_pre_exp: Fp[C]): SecretBool =
@@ -139,7 +125,7 @@ func isSquare_tonelli_shanks[C](
   ## Tonelli-Shanks based square root and inverse square root
   ##
   ## a^((p-1-2^e)/(2*2^e))
-  const e = C.tsGet(twoAdicity)
+  const e = C.tonelliShanks(twoAdicity)
   var r {.noInit.}: Fp[C]
   r.square(a_pre_exp) # a^(2(q-1-2^e)/(2*2^e)) = a^((q-1)/2^e - 1)
   r *= a              # a^((q-1)/2^e)
@@ -169,13 +155,13 @@ func sqrt_invsqrt_tonelli_shanks[C](
   template z: untyped = a_pre_exp
   template r: untyped = invsqrt
   var t {.noInit.}: Fp[C]
-  const e = C.tsGet(twoAdicity)
+  const e = C.tonelliShanks(twoAdicity)
 
   t.square(z)
   t *= a
   r = z
   var b = t
-  var root = C.tsGet(root_of_unity)
+  var root = C.tonelliShanks(root_of_unity)
 
   var buf {.noInit.}: Fp[C]
 
diff --git a/constantine/curves/addchain_square_roots.nim b/constantine/curves/addchain_square_roots.nim
new file mode 100644
index 0000000..23081f0
--- /dev/null
+++ b/constantine/curves/addchain_square_roots.nim
@@ -0,0 +1,17 @@
+# 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
+  std/macros,
+  ../config/curves,
+  ./bls12_377_square_root
+
+{.experimental: "dynamicBindSym".}
+
+macro tonelliShanks*(C: static Curve, value: untyped): untyped =
+  return bindSym($C & "_TonelliShanks_" & $value)
diff --git a/constantine/curves/bls12_377_square_root.nim b/constantine/curves/bls12_377_square_root.nim
new file mode 100644
index 0000000..8f74af7
--- /dev/null
+++ b/constantine/curves/bls12_377_square_root.nim
@@ -0,0 +1,20 @@
+# 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
+  ../config/[curves, type_bigint, type_fp],
+  ../io/[io_bigints, io_fields]
+
+const
+  # with e = 2adicity
+  # p == s * 2^e + 1
+  # root_of_unity = smallest_quadratic_nonresidue^s
+  # exponent = (p-1-2^e)/2^e / 2
+  BLS12_377_TonelliShanks_exponent* = BigInt[330].fromHex"0x35c748c2f8a21d58c760b80d94292763445b3e601ea271e3de6c45f741290002e16ba88600000010a11"
+  BLS12_377_TonelliShanks_twoAdicity* = 46
+  BLS12_377_TonelliShanks_root_of_unity* = Fp[BLS12_377].fromHex"0x382d3d99cdbc5d8fe9dee6aa914b0ad14fcaca7022110ec6eaa2bc56228ac41ea03d28cc795186ba6b5ef26b00bbe8"