Use the utility instead.

library/OAuth1.php

@@ -528,7 +528,7 @@ class OAuthRequest
    */
   private static function generate_nonce()
   {
-    return bin2hex(random_bytes(16));
+    return Friendica\Util\Strings::getRandomHex(32);
   }
 }
 

src/Network/FKOAuthDataStore.php

@@ -29,7 +29,7 @@ class FKOAuthDataStore extends OAuthDataStore
 	 */
 	private static function genToken()
 	{
-		return bin2hex(random_bytes(16));
+		return Friendica\Util\Strings::getRandomHex(32);
 	}
 
 	/**