From dev tools we get :
```
window.encryptionKey = 'nosource';

function process(a, b) {
'use strict';
var len = Math.max(a.length, b.length);
var out = [];
for (var i = 0, ca, cb; i < len; i++) {
ca = a.charCodeAt(i % a.length);
cb = b.charCodeAt(i % b.length);
out.push(ca ^ cb);
}
return String.fromCharCode.apply(null, out);
}

(function (global) {
'use strict';
var formEl = document.getElementById('flag-form');
var inputEl = document.getElementById('flag');
var flag = 'Fg4GCRoHCQ4TFh0IBxENAE4qEgwHMBsfDiwJRQImHV8GQAwBDEYvV11BCA==';
formEl.addEventListener('submit', function (e) {
e.preventDefault();
if (btoa(process(inputEl.value, global.encryptionKey)) === flag) {
alert('Your flag is correct!');
} else {
alert('Incorrect, try again.');
}
});
})(window);
```
chaine is the flag decoded from base64 to ascii number equivalence
you can chack on asciitohex website
it is xor cipher
```
#! /usr/bin/python
chaine="22 14 6 9 26 7 9 14 19 22 29 8 7 17 13 0 78 42 18 12 7 48 27 31 14 44 9 69 2 38 29 95 6 64 12 1 12 70 47 87 93 65 8"
L=chaine.split(" ")
for i in range(len(L)):
L[i]=int(L[i])
print (L)

def process(b,L):
maxi=max(len(L),len(b))
liste=[]
for i in range(maxi):
ca = L[i % len(L)]
cb = ord(b[i % len(b)])
liste.append(ca ^ cb)
return liste

b="soupy"
X=process(b,L)
#flag ^ key = cipher
#cipher ^ key = flag
# cipher ^ flag = key
s=""
for u in X:
s+=str(chr(u))
print s

```