Trait subtle::ConstantTimeEq

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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§

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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§

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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.

Object Safety§

This trait is not object safe.

Implementations on Foreign Types§

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impl ConstantTimeEq for Ordering

Ordering is #[repr(i8)] making it possible to leverage i8::ct_eq.

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

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impl ConstantTimeEq for i8

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fn ct_eq(&self, other: &i8) -> Choice

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impl ConstantTimeEq for i16

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fn ct_eq(&self, other: &i16) -> Choice

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impl ConstantTimeEq for i32

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fn ct_eq(&self, other: &i32) -> Choice

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impl ConstantTimeEq for i64

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fn ct_eq(&self, other: &i64) -> Choice

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impl ConstantTimeEq for i128

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fn ct_eq(&self, other: &i128) -> Choice

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impl ConstantTimeEq for isize

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

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impl ConstantTimeEq for u8

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fn ct_eq(&self, other: &u8) -> Choice

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impl ConstantTimeEq for u16

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fn ct_eq(&self, other: &u16) -> Choice

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impl ConstantTimeEq for u32

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fn ct_eq(&self, other: &u32) -> Choice

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impl ConstantTimeEq for u64

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fn ct_eq(&self, other: &u64) -> Choice

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impl ConstantTimeEq for u128

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fn ct_eq(&self, other: &u128) -> Choice

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impl ConstantTimeEq for usize

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

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impl<T: ConstantTimeEq> ConstantTimeEq for [T]

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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);

Implementors§