XOR cipher decryption in Javascript

Question

I have a base64 string that I have to decode, which is AwELBwc= . Using the XOR cipher key given to me, which is 26364 , I have to decode the string to get a number, which I already know ( 7813 ).

How would this be done in Javascript, where you take a base64-encoded string, run it through a XOR cipher with a known key, then output the result?

Answer 1

This code should do what you want:

 function base64ToArray(base64String) { var bstr = atob(base64String); var bytes = []; for (var i = 0; i < bstr.length; i++) { bytes.push(bstr.charCodeAt(i)); } return bytes; } let key = [2,6,3,6,4]; let cipherTextBase64 = 'AwELBwc='; let cipherTextBytes = base64ToArray(cipherTextBase64); let result = key.map((value,index) => { return value ^ cipherTextBytes[index]; }); document.getElementById('output').innerHTML = 'Result: ' + result.join(); console.log('Result: ', result); 

 <div id="output"> </div> 

Answer 2

The function below is inspired by the xor character by character method that Terry Lennox used in his answer.

 function xorDecryptBase64(base64string, cipher) { let keys = cipher.toString().split(''); let charCodes = atob(base64string).split('') .map(function(c){return c.charCodeAt(0)}); return Number(charCodes .map(function(v,i){return v ^ keys[i%keys.length]}) .slice(1).join('') ); } console.log(xorDecryptBase64('AwELBwc=', 26364)); console.log(xorDecryptBase64('AwAFAAIEAA==', 26364));