Randomize context on initialization

Signed-off-by: Sebastian Geisler <sebastian@blockstream.io>

Cargo.toml

@@ -29,7 +29,7 @@ rand-std = ["rand/std"]
 recovery = ["secp256k1-sys/recovery"]
 endomorphism = ["secp256k1-sys/endomorphism"]
 lowmemory = ["secp256k1-sys/lowmemory"]
-global-context = []
+global-context = ["std", "rand"]
 
 # Use this feature to not compile the bundled libsecp256k1 C symbols,
 # but use external ones. Use this only if you know what you are doing!

src/context.rs

@@ -31,7 +31,9 @@ pub mod global {
             static ONCE: Once = Once::new();
             static mut CONTEXT: Option<Secp256k1<All>> = None;
             ONCE.call_once(|| unsafe {
-                CONTEXT = Some(Secp256k1::new());
+                let mut ctx = Secp256k1::new();
+                ctx.randomize(&mut rand::thread_rng());
+                CONTEXT = Some(ctx);
             });
             unsafe { CONTEXT.as_ref().unwrap() }
         }