secp256k1

commit aae76295f8d86754de5a4560e4d6c7f2213ac5e6
parent 5873f4b163896cd7b7197c9d9f5fb3683a9e8aaa
Author: Jared Tobin <jared@jtobin.io>
Date:   Tue, 17 Jun 2025 14:47:52 +0400

lib: make parse_int256 total

Diffstat:
M
bench/Main.hs
 | 
23
++++++++++++++---------
M
bench/Weight.hs
 | 
11
++++++++---
M
lib/Crypto/Curve/Secp256k1.hs
 | 
9
++++-----

3 files changed, 26 insertions(+), 17 deletions(-)
diff --git a/bench/Main.hs b/bench/Main.hs
@@ -28,6 +28,11 @@ main = defaultMain [
   , ecdh
   ]
 
+parse_int256 :: BS.ByteString -> Integer
+parse_int256 bs = case S.parse_int256 bs of
+  Nothing -> error "bang"
+  Just s -> s
+
 remQ :: Benchmark
 remQ = env setup $ \x ->
     bgroup "remQ (remainder modulo _CURVE_Q)" [
@@ -35,7 +40,7 @@ remQ = env setup $ \x ->
     , bench "remQ (2 ^ 255 - 19)" $ nf S.remQ x
     ]
   where
-    setup = pure . S.parse_int256 $ B16.decodeLenient
+    setup = pure . parse_int256 $ B16.decodeLenient
       "7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffed"
 
 parse_point :: Benchmark
@@ -48,8 +53,8 @@ parse_point = bgroup "parse_point" [
 parse_integer :: Benchmark
 parse_integer = env setup $ \ ~(small, big) ->
     bgroup "parse_int256" [
-      bench "parse_int256 (small)" $ nf S.parse_int256 small
-    , bench "parse_int256 (big)" $ nf S.parse_int256 big
+      bench "parse_int256 (small)" $ nf parse_int256 small
+    , bench "parse_int256 (big)" $ nf parse_int256 big
     ]
   where
     setup = do
@@ -73,7 +78,7 @@ mul = env setup $ \x ->
     , bench "(2 ^ 255 - 19) G" $ nf (S.mul S._CURVE_G) x
     ]
   where
-    setup = pure . S.parse_int256 $ B16.decodeLenient
+    setup = pure . parse_int256 $ B16.decodeLenient
       "7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffed"
 
 precompute :: Benchmark
@@ -88,7 +93,7 @@ mul_wnaf = env setup $ \ ~(tex, x) ->
   where
     setup = do
       let !tex = S.precompute
-          !int = S.parse_int256 $ B16.decodeLenient
+          !int = parse_int256 $ B16.decodeLenient
             "7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffed"
       pure (tex, int)
 
@@ -103,7 +108,7 @@ derive_pub = env setup $ \ ~(tex, x) ->
   where
     setup = do
       let !tex = S.precompute
-          !int = S.parse_int256 $ B16.decodeLenient
+          !int = parse_int256 $ B16.decodeLenient
             "7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffed"
       pure (tex, int)
 
@@ -120,7 +125,7 @@ schnorr = env setup $ \ ~(tex, big) ->
   where
     setup = do
       let !tex = S.precompute
-          !int = S.parse_int256 $ B16.decodeLenient
+          !int = parse_int256 $ B16.decodeLenient
             "7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffed"
       pure (tex, int)
 
@@ -137,7 +142,7 @@ ecdsa = env setup $ \ ~(tex, big, pub, msg, sig) ->
   where
     setup = do
       let !tex = S.precompute
-          big = S.parse_int256 $ B16.decodeLenient
+          big = parse_int256 $ B16.decodeLenient
             "7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffed"
           Just pub = S.derive_pub big
           msg = "i approve of this message"
@@ -203,7 +208,7 @@ t = case S.parse_point t_bs of
   Just !pt -> pt
 
 s_sk :: Integer
-s_sk = S.parse_int256 . B16.decodeLenient $
+s_sk = parse_int256 . B16.decodeLenient $
   "B7E151628AED2A6ABF7158809CF4F3C762E7160F38B4DA56A784D9045190CFEF"
 
 s_sig :: BS.ByteString
diff --git a/bench/Weight.hs b/bench/Weight.hs
@@ -15,6 +15,11 @@ instance NFData S.Affine
 instance NFData S.ECDSA
 instance NFData S.Context
 
+parse_int :: BS.ByteString -> Integer
+parse_int bs = case S.parse_int256 bs of
+  Nothing -> error "bang"
+  Just v -> v
+
 big :: Integer
 big = 0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffed
 
@@ -42,8 +47,8 @@ remQ = W.wgroup "remQ" $ do
 
 parse_int256 :: W.Weigh ()
 parse_int256 = W.wgroup "parse_int256" $ do
-  W.func' "parse_int256 (small)" S.parse_int256 (BS.replicate 32 0x00)
-  W.func' "parse_int256 (big)" S.parse_int256 (BS.replicate 32 0xFF)
+  W.func' "parse_int (small)" parse_int (BS.replicate 32 0x00)
+  W.func' "parse_int (big)" parse_int (BS.replicate 32 0xFF)
 
 add :: W.Weigh ()
 add = W.wgroup " add" $ do
@@ -108,7 +113,7 @@ ecdh = W.wgroup "ecdh" $ do
       "bd02b9dfc8ef760708950bd972f2dc244893b61b6b46c3b19be1b2da7b034ac5"
 
 s_sk :: Integer
-s_sk = S.parse_int256 . B16.decodeLenient $
+s_sk = parse_int . B16.decodeLenient $
   "B7E151628AED2A6ABF7158809CF4F3C762E7160F38B4DA56A784D9045190CFEF"
 
 s_sig :: BS.ByteString
diff --git a/lib/Crypto/Curve/Secp256k1.hs b/lib/Crypto/Curve/Secp256k1.hs
@@ -703,11 +703,10 @@ derive_pub' = mul_wnaf
 --   >>> import qualified Data.ByteString as BS
 --   >>> parse_int256 (BS.replicate 32 0xFF)
 --   <2^256 - 1>
-parse_int256 :: BS.ByteString -> Integer
-parse_int256 bs
-  | BS.length bs /= 32 =
-      error "ppad-secp256k1 (parse_int256): requires exactly 32-byte input"
-  | otherwise = roll32 bs
+parse_int256 :: BS.ByteString -> Maybe Integer
+parse_int256 bs = do
+  guard (BS.length bs == 32)
+  pure $! roll32 bs
 
 -- | Parse compressed secp256k1 point (33 bytes), uncompressed point (65
 --   bytes), or BIP0340-style point (32 bytes).