These are valid questions a lot of people new to Rust have, so:

1. Rust is "backward compatible" in the sense that Rust code can use C libraries and C code can use Rust libraries - both ways via CFFI [1]. Security gaurentees only apply to the Rust code.

2. We've tired static and dynamic analysis of C to find security bugs for decades, there has been a plethora of research and commercial tools in the space. None fix the problem like Rust does [2].

[1] https://michael-f-bryan.github.io/rust-ffi-guide/ [2] https://msrc-blog.microsoft.com/2019/07/18/we-need-a-safer-s...