rustcrypto_secretkey_demo.rs

#[derive(Clone, Debug)] // Cloneable
pub struct SecretKey {
    scalar: [u64; 2] // Copyable
}

impl Drop for SecretKey {
    fn drop(&mut self) {
        unsafe {
            core::ptr::write_volatile(&mut self.scalar, [0u64; 2]);
            core::sync::atomic::compiler_fence(core::sync::atomic::Ordering::SeqCst);
        }
        println!("Zeroized: {:?}", self);        
    }
}

let (a, ptr) = {
    let b = SecretKey {
        scalar: [43, 32]
        };

    let addr_b = b.scalar.as_ptr();

    println!("Creation address: {:?}", addr_b);

    (b, addr_b)
};

let addr_a = a.scalar.as_ptr();
println!("Returned address: {:?}", addr_a);

println!("Value before zeroizing: {:?}", &a);

drop(a);

let val = unsafe {
    core::slice::from_raw_parts(ptr, 2)
    };

println!("Value at creation address: {:?}", val);