csecp256k1

commit ed95eae3e2fc1573cea860bb9eb09875e1ed25cd
parent fd8257987717027b2b7658b2466cc06a0f62460b
Author: Jared Tobin <jared@jtobin.io>
Date:   Tue, 12 Mar 2024 17:44:17 +0400

lib: add warning re: context usage

Diffstat:
M
lib/Crypto/Secp256k1.hs
 | 
14
++++++++++++++

1 file changed, 14 insertions(+), 0 deletions(-)
diff --git a/lib/Crypto/Secp256k1.hs b/lib/Crypto/Secp256k1.hs
@@ -156,6 +156,17 @@ instance Exception Secp256k1Exception
 --   that has /not/ been randomized, and so /doesn't/ offer additional
 --   side-channel attack protection. For that, use 'wrcontext'.
 --
+--   Do /not/ attempt to use the created 'Context' value outside
+--   of a 'wcontext' or 'wrcontext' block, as the internal
+--   bitcoin-core/secp256k1 context will have been destroyed by then.
+--   For example, don't be cheeky and do something like:
+--
+--   > do
+--   >   context <- wcontext pure
+--   >   derive_pub context seckey
+--
+--   unless you like segfaults.
+--
 --   >>> wcontext $ \tex -> parse_pub tex bytestring
 --   "<bitcoin-core/secp256k1 public key>"
 wcontext
@@ -176,6 +187,9 @@ wcontext = bracket create destroy where
 --   Use this function to execute computations that may benefit from
 --   additional side-channel attack protection.
 --
+--   As with 'wcontext', do /not/ attempt to use a created 'Context'
+--   value outside of the 'wrcontext' block.
+--
 --   >>> wrcontext entropy $ \tex -> sign tex sec msg
 --   "<bitcoin-core/secp256k1 signature>"
 wrcontext