> wrap an existing C crypto library
I know it's mostly semantics but calling C from C++ still requires some wrapping(extern "C", integrating build system, etc).
I've found with bindgen unless there's some crazy macro shenanigans going on it's actually quicker for me to integrate C libraries into Rust then wrangling CMake/Make/etc. The C FFI is very much a first-class citizen in Rust.
Even doubly so if we're talking about a cross-platform library.