Trait ConstantTimeGreater

pub trait ConstantTimeGreater {
    // Required method
    fn ct_gt(&self, other: &Self) -> Choice;
}

A type which can be compared in some manner and be determined to be greater than another of the same type.

Required Methods

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

Determine whether self > other.

The bitwise-NOT of the return value of this function should be usable to determine if self <= other.

This function should execute in constant time.

Returns

A Choice with a set bit if self > other, and with no set bits otherwise.

Example

use subtle_ng::ConstantTimeGreater;

let x: u8 = 13;
let y: u8 = 42;

let x_gt_y = x.ct_gt(&y);

assert_eq!(x_gt_y.unwrap_u8(), 0);

let y_gt_x = y.ct_gt(&x);

assert_eq!(y_gt_x.unwrap_u8(), 1);

let x_gt_x = x.ct_gt(&x);

assert_eq!(x_gt_x.unwrap_u8(), 0);

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl ConstantTimeGreater for u8

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

Returns Choice::from(1) iff x > y, and Choice::from(0) iff x <= y.

Note

This algoritm would also work for signed integers if we first flip the top bit, e.g. let x: u8 = x ^ 0x80, etc.

impl ConstantTimeGreater for u16

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

Returns Choice::from(1) iff x > y, and Choice::from(0) iff x <= y.

Note

This algoritm would also work for signed integers if we first flip the top bit, e.g. let x: u8 = x ^ 0x80, etc.

impl ConstantTimeGreater for u32

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

Returns Choice::from(1) iff x > y, and Choice::from(0) iff x <= y.

Note

This algoritm would also work for signed integers if we first flip the top bit, e.g. let x: u8 = x ^ 0x80, etc.

impl ConstantTimeGreater for u64

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

Returns Choice::from(1) iff x > y, and Choice::from(0) iff x <= y.

Note

This algoritm would also work for signed integers if we first flip the top bit, e.g. let x: u8 = x ^ 0x80, etc.

impl ConstantTimeGreater for u128

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

Returns Choice::from(1) iff x > y, and Choice::from(0) iff x <= y.

Note

This algoritm would also work for signed integers if we first flip the top bit, e.g. let x: u8 = x ^ 0x80, etc.

Implementors