Trait subtle::ConstantTimeEq

source ·

pub trait ConstantTimeEq {
    // Required method
    fn ct_eq(&self, other: &Self) -> Choice;

    // Provided method
    fn ct_ne(&self, other: &Self) -> Choice { ... }
}

Expand description

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

Example

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§

source

fn ct_eq(&self, other: &Self) -> Choice

Determine if two items are equal.

The ct_eq function should execute in constant time.

Returns

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

Provided Methods§

source

fn ct_ne(&self, other: &Self) -> Choice

Determine if two items are NOT equal.

The ct_ne function should execute in constant time.

Returns

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

Implementations on Foreign Types§

source §

fn ct_eq(&self, _rhs: &[T]) -> Choice

Check whether two slices of ConstantTimeEq types are equal.

Note

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);