XOR is a Swift Library that allows you to compute the eXclusive OR of two Integer arrays.

Documentation

What is XOR ?

Exclusive OR (XOR) compares the bits of two numbers. The operations returns a new number whose bits are set to 1 where the input bits are different and are set to 0 where the input bits are the same.

Image courtesy of The Swift Programming Language Book, CC by 4.0

This algorithm is often used for cryptography and math.

Installation

Swift Package Manager

Add this line to your Package.swift file:

.Package(url: "https://github.com/alexaubry/XOR.git", majorVersion: 1, minor: 0)

Usage

You can compute the XOR of any Array whose Element type conform to Swift's native Integer protocol (that is Int, UInt8, ...).

To do so, use the xor(key:) method on an Integer array.

let array = [0x1a,0x2b,0x3c,0x4d,0x5e,0x6f]
let key = [0x84,0x1b,0x76,0x91,0xfa,0x55]

let result = array.xor(key: key)

// result = [0x9e,0x30,0x4a,0xdc,0xa4,0x3a]

You can also get the original message back by calling the xor(key:) method on a XOR result using the same key.

let originalMessage = result.xor(key: key)
// originalMessage = [0x1a,0x2b,0x3c,0x4d,0x5e,0x6f]

Implementation Details

• If a component (either the receiver or the key) has a smaller length that the other component, padding will be added to it. This allows you to have a key longer than the message, and vice-versa.

Examples:

let message = [0x1a,0x2b]
let key = [0x3c,0x4d,0x5e,0x6f]
// message will be XOR-ed as [0x00,0x00,0x1a,0x2b]

let message = [0x1a,0x2b,0x3c,0x4d]
let key = [0x5e,0x6f]
// the key will be [0x00,0x00,0x5e,0x6f]

• Any common prefix between the receiver and the key will be stripped, in order to remove any leading 0s from the output.

Example:

let message = [0x1a,0x2b,0x3c]
let key = [0x1a,0x4d,0x5e]
// message will be XOR-ed as [0x2b,0x3c] and the key will be [0x4d,0x5e]

Enjoy❓