Zeroing out memory isn't sufficient, as discussed here: http://www.daemonology.net/blog/2014-09-06-zeroing-buffers-i...

That said, this was discussed on reddit[0], it sounds like there is a way to guarantee that you did zero out memory (but not necessarily copies of that memory, as discussed in the link above), and because Rust is intended to be memory safe, it's not as much of an issue if you don't/can't.

http://www.reddit.com/r/rust/comments/2fnb82/zeroing_buffers...