diff --git a/devscripts/youtube_genalgo.py b/devscripts/youtube_genalgo.py
index f91e8855d3..3b90a2fede 100644
--- a/devscripts/youtube_genalgo.py
+++ b/devscripts/youtube_genalgo.py
@@ -27,15 +27,15 @@
     # 87
     ("qwertyuioplkjhgfdsazxcvbnm1234567890QWERTYUIOPLKJHGFDSAZXCVBNM!@#$^&*()_-+={[]}|:;?/>.<",
      "uioplkjhgfdsazxcvbnm1t34567890QWE2TYUIOPLKJHGFDSAZXCVeNM!@#$^&*()_-+={[]}|:;?/>.<"),
-    # 86 - vfluy6kdb 2013/09/06
+    # 86 - vflHql6Pr 2013/09/24
     ("qwertyuioplkjhgfdsazxcvbnm1234567890QWERTYUIOPLKJHGFDSAZXCVBNM!@#$%^&*()_-+={[|};?/>.<",
-     "yuioplkjhgfdsazxcvbnm12345678q0QWrRTYUIOELKJHGFD-AZXCVBNM!@#$%^&*()_<+={[|};?/>.S"),
+     ";}|[{=+-d)(*&^%$#@!MNBVCXZASDFGHJKLPOIUYT_EWQ0987654321mnbvcxzas/fghjklpoiuytrewq"),
     # 85 - vflkuzxcs 2013/09/11
     ('0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!"#$%&\'()*+,-./:;<=>?@[',
      '3456789a0cdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRS[UVWXYZ!"#$%&\'()*+,-./:;<=>?@'),
-    # 84 - vflg0g8PQ 2013/08/29 (sporadic)
+    # 84 - vflHql6Pr 2013/09/24 (sporadic)
     ("qwertyuioplkjhgfdsazxcvbnm1234567890QWERTYUIOPLKJHGFDSAZXCVBNM!@#$%^&*()_-+={[};?>.<",
-     ">?;}[{=+-_)(*&^%$#@!MNBVCXZASDFGHJKLPOIUYTREWq0987654321mnbvcxzasdfghjklpoiuytr"),
+     "}[{=+-_)g*&^%$#@!MNBVCXZASDFGHJKLPOIUYTRE(Q0987654321mnbvcxzasdf?hjklpoiuytrewq"),
     # 83
     ("qwertyuioplkjhgfdsazxcvbnm1234567890QWERTYUIOPLKJHGFDSAZXCVBNM!#$%^&*()_+={[};?/>.<",
      ".>/?;}[{=+_)(*&^%<#!MNBVCXZASPFGHJKLwOIUYTREWQ0987654321mnbvcxzasdfghjklpoiuytreq"),
diff --git a/youtube_dl/extractor/youtube.py b/youtube_dl/extractor/youtube.py
index 47d5cb7ff8..ec1cf8d30c 100644
--- a/youtube_dl/extractor/youtube.py
+++ b/youtube_dl/extractor/youtube.py
@@ -431,11 +431,11 @@ def _decrypt_signature(self, s):
         elif len(s) == 87:
             return s[6:27] + s[4] + s[28:39] + s[27] + s[40:59] + s[2] + s[60:]
         elif len(s) == 86:
-            return s[5:34] + s[0] + s[35:38] + s[3] + s[39:45] + s[38] + s[46:53] + s[73] + s[54:73] + s[85] + s[74:85] + s[53]
+            return s[80:72:-1] + s[16] + s[71:39:-1] + s[72] + s[38:16:-1] + s[82] + s[:16][::-1]
         elif len(s) == 85:
             return s[3:11] + s[0] + s[12:55] + s[84] + s[56:84]
         elif len(s) == 84:
-            return s[81:36:-1] + s[0] + s[35:2:-1]
+            return s[78:70:-1] + s[14] + s[69:37:-1] + s[70] + s[36:14:-1] + s[80] + s[:14][::-1]
         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: