This is vpat101.exe readme file.

Vpat101.exe is an add-on utility for TorDisk images.
It fix a security bug in disk images created by tordisk
versions prior to 1.01. Without applaying this patch
to old disk images TorDisk v 1.01 can't mount it
(Data error: Cyclic Redundancy Check error while mounting).

This patch is not requiered to disk images created by
TorDisk v 1.01 and later.

To apply a patch to disk image run it in NT's command 
dos box prompt with the disk image file name as the 
only parameter, for example,

$ vpat101.exe c:\mysecret.dat

Remember, that this utility reqiered a crypt32b.dll from
crypter distribution.

This utility ask you a disk image passphrase, and create
a backup header data - 1 Kb file with old unpatched
header named (in this example) "mysecret.b01".
You can (and should, due to security reasons) remove
this backup file AFTER you ensure that newer patched
image are valid and could be mounted by current TorDisk 
release (please, run a chkdsk after disk mounting).
In case of failure you can copy over this backup header
to file with 0 offset.

This utility have one bug - it fails and call DrWatson
if you specify an invalid password.

In any problem please call author, tor@crec.mipt.ru.

Appendix:
---------
security bug fixed by vpat101.exe description:
The initialization vector (IV) for master disk key
due to program mistake is fixed and predictable
(but should be random and non-predictable).
This is not so serious bug giving a backdoor for
intruder, it only weakened overall disk security.
This bug don't influence to key's and encryption
quality.