removing hex2bin to avoid having to add code for this in JS and to not introduce a dependency on paste IDs always having to be hex strings

lib/Model/Paste.php

@@ -117,7 +117,7 @@ class Paste extends AbstractModel
         // if a challenge was sent, we store the HMAC of paste ID & challenge
         if (array_key_exists('challenge', $this->_data['meta'])) {
             $this->_data['meta']['challenge'] = base64_encode(hash_hmac(
-                'sha256', hex2bin($this->getId()), base64_decode($this->_data['meta']['challenge']), true
+                'sha256', $this->getId(), base64_decode($this->_data['meta']['challenge']), true
             ));
         }