diff --git a/DeDRM_plugin/ineptepub.py b/DeDRM_plugin/ineptepub.py
index fb67cb4..8bab717 100644
--- a/DeDRM_plugin/ineptepub.py
+++ b/DeDRM_plugin/ineptepub.py
@@ -415,12 +415,12 @@ def decryptBook(userkey, inpath, outpath):
                 return 1
             bookkey = rsa.decrypt(codecs.decode(bookkey.encode('ascii'), 'base64'))
             # Padded as per RSAES-PKCS1-v1_5
-            if len(bookkey) != 16:
-                if bookkey[-17] != '\x00' and bookkey[-17] != 0:
+            if len(bookkey) > 16:
+                if bookkey[-17] == '\x00' or bookkey[-17] == 0:
+                    bookkey = bookkey[-16:]
+                else:
                     print("Could not decrypt {0:s}. Wrong key".format(os.path.basename(inpath)))
                     return 2
-                else:
-                    bookkey = bookkey[-16:]
             encryption = inf.read('META-INF/encryption.xml')
             decryptor = Decryptor(bookkey, encryption)
             kwds = dict(compression=ZIP_DEFLATED, allowZip64=False)
diff --git a/DeDRM_plugin/ineptpdf.py b/DeDRM_plugin/ineptpdf.py
index 17ccdcf..669856c 100755
--- a/DeDRM_plugin/ineptpdf.py
+++ b/DeDRM_plugin/ineptpdf.py
@@ -1599,11 +1599,10 @@ class PDFDocument(object):
         bookkey = rsa.decrypt(bookkey)
         #if bookkey[0] != 2:
         #    raise ADEPTError('error decrypting book session key')
-        try:
-        	index = bookkey.index(b'\0') + 1
-        	bookkey = bookkey[index:]
-        except ValueError:
-        	pass
+        if len(bookkey) > 16:
+            if bookkey[-17] == '\x00' or bookkey[-17] == 0:
+                bookkey = bookkey[-16:]
+                length = 16
         ebx_V = int_value(param.get('V', 4))
         ebx_type = int_value(param.get('EBX_ENCRYPTIONTYPE', 6))
         # added because of improper booktype / decryption book session key errors