set-1-challenge-2.md

Fixed XOR

The challenge

Write a function that takes two equal-length buffers and produces their XOR combination.

If your function works properly, then when you feed it the string:

1c0111001f010100061a024b53535009181c

... after hex decoding, and when XOR'd against:

686974207468652062756c6c277320657965

... should produce:

746865206b696420646f6e277420706c6179

The solution

NodeJS:

const aString = "1c0111001f010100061a024b53535009181c"
const bString = "686974207468652062756c6c277320657965"
const aBuffer = Buffer.from(aString, "hex")
const bBuffer = Buffer.from(bString, "hex")

const XORString = aBuffer.map((a,i) => a ^ bBuffer[i]).toString("hex")
console.log(XORString)

Browser:

const parseHex = string => parseInt(string, 16)

const aString = "1c0111001f010100061a024b53535009181c"
const bString = "686974207468652062756c6c277320657965"
const aBuffer = aString.match(/.{2}/g).map(parseHex)
const bBuffer = bString.match(/.{2}/g).map(parseHex)

const XORString = aBuffer.map((a,i) => (a ^ bBuffer[i]).toString(16)).join("")
console.log(XORString)