## modinverse

Small library for finding the modular multiplicative inverses

### 2 releases

Uses old Rust 2015

 0.1.1 Dec 8, 2018 Feb 8, 2017

#851 in Cryptography

Used in 8 crates

5KB

# rust-modinverse

Small library for finding the modular multiplicative inverses. Also has an implementation of the extended Euclidean algorithm built in.

## `modinverse`

Calculates the modular multiplicative inverse x of an integer a such that ax ≡ 1 (mod m).

Such an integer may not exist. If so, this function will return `None`. Otherwise, the inverse will be returned wrapped up in a `Some`.

``````use modinverse::modinverse;

let does_exist = modinverse(3, 26);
let does_not_exist = modinverse(4, 32);

match does_exist {
Some(x) => assert_eq!(x, 9),
None => panic!("modinverse() didn't work as expected"),
}

match does_not_exist {
Some(x) => panic!("modinverse() found an inverse when it shouldn't have"),
None => {},
}
``````

## `egcd`

Finds the greatest common denominator of two integers a and b, and two integers x and y such that ax + by is the greatest common denominator of a and b (Bézout coefficients).

This function is an implementation of the extended Euclidean algorithm.

``````use modinverse::egcd;

let a = 26;
let b = 3;
let (g, x, y) = egcd(a, b);

assert_eq!(g, 1);
assert_eq!(x, -1);
assert_eq!(y, 9);
assert_eq!((a * x) + (b * y), g);
``````

~205KB