diff --git a/oletools/common/errors.py b/oletools/common/errors.py
index 4ee4cb1..f492011 100644
--- a/oletools/common/errors.py
+++ b/oletools/common/errors.py
@@ -4,10 +4,33 @@ Errors used in several tools to avoid duplication
 .. codeauthor:: Intra2net AG <info@intra2net.com>
 """
 
-class FileIsEncryptedError(ValueError):
+class CryptoErrorBase(ValueError):
+    """Base class for crypto-based exceptions."""
+    pass
+
+class UnsupportedEncryptionError(CryptoErrorBase):
     """Exception thrown if file is encrypted and cannot deal with it."""
-    # see also: same class in olevba[3] and record_base
     def __init__(self, filename=None):
-        super(FileIsEncryptedError, self).__init__(
+        super(UnsupportedEncryptionError, self).__init__(
             'Office file {}is encrypted, not yet supported'
             .format('' if filename is None else filename + ' '))
+
+
+class WrongEncryptionPassword(CryptoErrorBase):
+    """Exception thrown if encryption could be handled but passwords wrong."""
+    def __init__(self, filename=None):
+        super(WrongEncryptionPassword, self).__init__(
+            'Given passwords could not decrypt office file{}'
+            .format('' if filename is None else ' ' + filename))
+
+
+class MaxCryptoNestingReached(CryptoErrorBase):
+    """
+    Exception thrown if decryption is too deeply layered.
+
+    (...or decrypt code creates inf loop)
+    """
+    def __init__(self, n_layers, filename=None):
+        super(MaxCryptoNestingReached, self).__init__(
+            'Encountered more than {} layers of encryption for office file{}'
+            .format(n_layers, '' if filename is None else ' ' + filename))