Add README note about key validity assertions at the FFI boundary

diff --git a/lightning-c-bindings/README.md b/lightning-c-bindings/README.md
index 72426bdf334ed0f265cd7a4220c7c4381b1b86c0..0c221c7c6ad44ad4c2d6c4b46b34d176e2a7924d 100644 (file)
--- a/lightning-c-bindings/README.md
+++ b/lightning-c-bindings/README.md
@@ -218,6 +218,9 @@ These include:
          ...
    } LDKChannelKeys;
    ```
+ * Private and public keys are asserted valid at the FFI boundary. Thus, before passing any
+   (untrusted) private or public key material across the boundary, ensure that they represent valid
+   (ie in-range) keys.
    
 **It is highly recommended that you test any code which relies on the C (or C++) bindings in
 valgrind, AddressSanitizer, MemorySanitizer, or other similar tools to ensure correctness.**