diff --git a/DeDRM_plugin/ineptpdf.py b/DeDRM_plugin/ineptpdf.py
index 8ce9023..9bbf092 100755
--- a/DeDRM_plugin/ineptpdf.py
+++ b/DeDRM_plugin/ineptpdf.py
@@ -427,7 +427,7 @@ def _load_crypto_pycrypto():
             return total
 
         def decrypt(self, data):
-            return _PKCS1_v1_5.new(self._rsa).decrypt(data, b'')
+            return _PKCS1_v1_5.new(self._rsa).decrypt(data, 172)
 
     return (ARC4, RSA, AES)
 
@@ -1901,9 +1901,6 @@ class PDFDocument(object):
         return
 
     def verify_book_key(self, bookkey):
-        if len(bookkey) <= 16:
-            return False
-
         if bookkey[-17] != '\x00' and bookkey[-17] != 0:
             # Byte not null, invalid result
             return False
@@ -1988,11 +1985,12 @@ class PDFDocument(object):
         bookkey = codecs.decode(bookkey.encode('utf-8'),'base64')
         bookkey = rsa.decrypt(bookkey)
 
-        if (self.verify_book_key(bookkey)):
-            bookkey = bookkey[-16:]
-            length = 16
-        else:
-            raise ADEPTError('error decrypting book session key')
+        if len(bookkey) > 16:
+            if (self.verify_book_key(bookkey)):
+                bookkey = bookkey[-16:]
+                length = 16
+            else:
+                raise ADEPTError('error decrypting book session key')
 
         ebx_V = int_value(param.get('V', 4))
         ebx_type = int_value(param.get('EBX_ENCRYPTIONTYPE', 6))