diff --git a/devscripts/youtube_genalgo.py b/devscripts/youtube_genalgo.py
index 014324439f..6f1d6ef99e 100644
--- a/devscripts/youtube_genalgo.py
+++ b/devscripts/youtube_genalgo.py
@@ -26,9 +26,9 @@
     # 85
     ("qwertyuioplkjhgfdsazxcvbnm1234567890QWERTYUIOPLKJHGFDSAZXCVBNM!@#$%^&*()_-+={[};?/>.<",
      ".>/?;}[{=+-_)(*&^%$#@!MNBVCXZASDFGHJKLPOIUYTREWQ0q876543r1mnbvcx9asdfghjklpoiuyt2"),
-    # 84
+    # 84 - vflh9ybst 2013/08/23 (sporadic)
     ("qwertyuioplkjhgfdsazxcvbnm1234567890QWERTYUIOPLKJHGFDSAZXCVBNM!@#$%^&*()_-+={[};?>.<",
-     "<.>?;}[{=+-_)(*&^%$#@!MNBVCXZASDFGHJKLPOIUYTREWQ09876543q1mnbvcxzasdfghjklpoiuew2"),
+     "yuioplkjhgfdsazxcvbnm1234567890QWERrYUIOPLKqHGFDSAZXCVBNM!@#$%^&*()_-+={[};?>.<"),
     # 83
     ("qwertyuioplkjhgfdsazxcvbnm1234567890QWERTYUIOPLKJHGFDSAZXCVBNM!#$%^&*()_+={[};?/>.<",
      ".>/?;}[{=+_)(*&^%<#!MNBVCXZASPFGHJKLwOIUYTREWQ0987654321mnbvcxzasdfghjklpoiuytreq"),
diff --git a/youtube_dl/extractor/youtube.py b/youtube_dl/extractor/youtube.py
index e4987b2b39..af01c9da02 100644
--- a/youtube_dl/extractor/youtube.py
+++ b/youtube_dl/extractor/youtube.py
@@ -427,7 +427,7 @@ def _decrypt_signature(self, s):
         elif len(s) == 85:
             return s[83:34:-1] + s[0] + s[33:27:-1] + s[3] + s[26:19:-1] + s[34] + s[18:3:-1] + s[27]
         elif len(s) == 84:
-            return s[83:27:-1] + s[0] + s[26:5:-1] + s[2:0:-1] + s[27]
+            return s[5:40] + s[3] + s[41:48] + s[0] + s[49:84]
         elif len(s) == 83:
             return s[81:64:-1] + s[82] + s[63:52:-1] + s[45] + s[51:45:-1] + s[1] + s[44:1:-1] + s[0]
         elif len(s) == 82: