pub trait ConstantTimeEq {
    fn ct_eq(&self, other: &Self) -> Choice;
Expand description

An Eq-like trait that produces a Choice instead of a bool.


use subtle::ConstantTimeEq;
let x: u8 = 5;
let y: u8 = 13;

assert_eq!(x.ct_eq(&y).unwrap_u8(), 0);
assert_eq!(x.ct_eq(&x).unwrap_u8(), 1);

Required methods

Determine if two items are equal.

The ct_eq function should execute in constant time.

  • Choice(1u8) if self == other;
  • Choice(0u8) if self != other.

Implementations on Foreign Types

Check whether two slices of ConstantTimeEq types are equal.


This function short-circuits if the lengths of the input slices are different. Otherwise, it should execute in time independent of the slice contents.

Since arrays coerce to slices, this function works with fixed-size arrays:

let a: [u8; 8] = [0,1,2,3,4,5,6,7];
let b: [u8; 8] = [0,1,2,3,0,1,2,3];

let a_eq_a = a.ct_eq(&a);
let a_eq_b = a.ct_eq(&b);

assert_eq!(a_eq_a.unwrap_u8(), 1);
assert_eq!(a_eq_b.unwrap_u8(), 0);