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1992-12-29
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Thunderbyte auto disk (de)cryptor. (C) 1992 Thunderbyte B.V.
Table of Contents
1. INTRODUCTION...................................... 2
1.1. Purpose of TbGarble......................... 2
1.2. A Quick start............................... 3
1.3. Benefits.................................... 3
2. USAGE OF THE PROGRAM.............................. 5
2.1. System requirements......................... 5
2.2. Program invocation.......................... 5
2.2.1. Invocation in Config.Sys.............. 5
2.3. Command line options........................ 6
2.3.1. help ................................. 6
2.3.2. remove ............................... 6
2.3.3. off .................................. 6
2.3.4. on ................................... 6
2.3.5. auto ................................. 6
2.3.6. write ................................ 7
2.3.7. query ................................ 7
2.4. Examples:................................... 7
2.5. Creating garbled disks...................... 7
2.6. The encryption key.......................... 7
2.7. The hardware garbler........................ 8
Page i
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Thunderbyte auto disk (de)cryptor. (C) 1992 Thunderbyte B.V.
1. INTRODUCTION
1.1. Purpose of TbGarble
TbGarble is an automatic disk encryptor and decryptor. It can
encrypt and decrypt diskettes while writing and reading on the
fly. No user action is required to convert the data.
Although most devices attached to a PC are specific and not
compatible with other devices of other machines, there is one sort
of device that is very exchangable: the diskettes and their drives.
Of course, due to their purpose it is quite normal that you can
share and exchange your disks with other people, but in some
environments this is undesirable.
Some companies like to exchange their data between their machines,
but not to the outside world. Other companies like to enable their
employees to take their work to home, but not to take games from
home to the company!
These requirements seem to be contradictory. How is it possible
to transport data from machine A to B, but make it impossible to
transport data from machine B to A? It's not important how, but
TbGarble makes it possible, and without increasing chances of
incompatibility or drive failures! TbGarble scrambles and
descrambles data being transferred from and to diskette drives on
the fly. TbGarble acts like a two-way automatic filter. It
determines itself whether a diskette is garbled or not, and
processes all transfers according to this diskette type.
The diskette type is determined while formatting the diskettes. If
the diskette is formatted while garbling was enabled, all future
data being transferred to that diskette will be garbled. Systems
without TbGarble are not able to read or write to those diskettes.
If the diskette is formatted while garbling was disabled, all
future data being transferred to the diskette will not be garbled.
Of course, if TbGarble is configured to process only garbled
diskettes at that time, the machine will not be able to transfer
data to this diskette, nor to read it.
Here are a few examples that will explain the purpose of TbGarble:
Example 1.
You own a company, and the company processes very delicate
data. You don't want employees to take the data to their
homes. One option is to disable all floppy drives, but that
makes it impossible to update data on the machines and to
install new software. A good solution would be to install
TbGarble and configure it to read from both garbled and normal
diskettes, but write only to garbled diskettes.
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Thunderbyte auto disk (de)cryptor. (C) 1992 Thunderbyte B.V.
Example 2.
You own a company, and the company processes very delicate
data. You don't want employees to take the data to their
homes, nor should they be able to install new software (and
possible viruses!) or things like that. A good solution would
be to install TbGarble and configure it to process only garbled
diskettes. The machines will not be able to write or read from
normal diskettes, but it is still possible to exchange data
between machines owned by the company.
Example 3.
You own a company, and employees should be able to take data to
their homes, install new software and so on. However, there are
also some machines that processes accounts, and of course, you
don't want your employees to install software on those
machines. It would be handy on the other hand if it was
possible to exchange data between the "account machines" and the
normal machines. A solution would be to install TbGarble on the
"account machines" and configure them to process only garbled
diskettes. To enable the other machines to exchange data with
these machines you should also install TbGarble on the normal
machines and configure them to process both normal and garbled
diskettes.
1.2. A Quick start
Although we highly recommend a complete reading of this manual, here
are some directions for a quick run of TbGarble:
To load TbGarble type "TbGarble" and press return.
The invocation syntax is:
TBGARBLE [<options>]...
For fast online help type "TbGarble ?" or "TbGarble help".
1.3. Benefits
TbGarble has several advantages over other disk encryptors:
+ It does not require any user intervention. Disks are encrypted
or decrypted on the fly while reading and writing data.
+ TbGarble can be configured to maintain compatibility with
'normal' disks. In this case TbGarble will determine
automatically whether the diskette in the drive is encrypted or
not, and decrypt data only when the disk is encrypted.
+ Because disks are decrypted on the fly, TbGarble will not write
to the disk when decrypting data. The write-protect tab doesn't
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Thunderbyte auto disk (de)cryptor. (C) 1992 Thunderbyte B.V.
need to be removed. There is no increased risk of data
corruption.
+ TbGarble performs very fast. In fact, it is so fast that you
will not be able to detect its presence.
+ TbGarble uses less than 600 bytes of memory, and it can be
loaded into upper memory.
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Thunderbyte auto disk (de)cryptor. (C) 1992 Thunderbyte B.V.
2. USAGE OF THE PROGRAM
2.1. System requirements
TbGarble runs perfectly on standard machines, in line with our
philosophy that there should be a limit to limitations.
+ TbGarble can be executed under DOS version 3.00 (and all later
versions). However, Dos 5.0 or higher is recommended, since
TbGarble has been optimized and designed primarily for use with
these DOS versions.
+ TbGarble requires about 4 Kb of free memory to be invoked.
After termination it requires only 600 bytes of memory.
2.2. Program invocation
It is recommended to invoke TbGarble automatically from within your
Config.Sys or Autoexec.Bat file.
There are three possible ways to invoke TbGarble:
To invoke TbGarble from the DOS prompt or within the Autoexec.Bat
file:
<path>TbGarble
To invoke TbGarble from the Config.Sys as a TSR (Dos 4+):
Install=<path>TbGarble.Exe
To invoke TbGarble from the Config.Sys as a device driver:
Device=<path>TbGarble.Exe
TbGarble should always work correctly after being started from
within the Autoexec.Bat. The "Install=" Config.Sys command is
NOT available in DOS 3.xx.
In addition to the three invocation possibilities DOS 5+ users can
"highload" TbGarble into an UMB (upper memory block) if it is
available:
LoadHigh <path>TbGarble.Exe
Within the Config.Sys file TbGarble can also be loaded high:
DeviceHigh=<path>TbGarble.Exe
2.2.1. Invocation in Config.Sys
-> Invoking TbGarble as a device driver does not work in all OEM
versions of DOS. If it doesn't work use the "Install=" command
or load TbGarble from within the Autoexec.Bat.
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Thunderbyte auto disk (de)cryptor. (C) 1992 Thunderbyte B.V.
2.3. Command line options
It is possible to specify options on the command line.
optionword parameter short explanation
---------- --------- ----- ----------------------------
help ? =display this helpscreen
remove r =remove TbMem from memory
off [=<driveID>] d =read and write only normal
on [=<driveID>] e =read and write only garbled
auto [=<driveID>] a =read and write garbled and normal
write [=<driveID>] w =read garbled and normal, write only garbled
query q =display diskette types
TbGarble will by default use option 'auto' for both diskette
drives.
2.3.1. help (?)
If you specify this option TbGarble will show you the brief help as
shown above.
2.3.2. remove (r)
This option can be used to remove the resident part of TbGarble
from your system's memory. All memory used by TbGarble will be
released. Unfortunately, the removal of a TSR (like TbGarble) is
not always possible. TbGarble checks whether it is safe to remove
the resident part from memory. If it is not safe it just disables
TbGarble. A TSR can not be removed if another TSR has been started
after it. If this happens with TbGarble it will completely disable
itself.
2.3.3. off (d)
This option can be used to disable TbGarble. If you disable
TbGarble, the machine will behave as if TbGarble wasn't loaded: it
is no longer possible to use encrypted disks.
You can optionally specify the drive for which this option applies.
2.3.4. on (e)
If you specify this option, TbGarble will encrypt data to be
written to disk, and decrypt data read from disk. It will not check
if the disk is actually encrypted, so normal disks can not be read
in this case.
You can optionally specify the drive for which this option applies.
2.3.5. auto (a)
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Thunderbyte auto disk (de)cryptor. (C) 1992 Thunderbyte B.V.
If you specify this option, TbGarble will automatically detect
whether a disk in the drive is encrypted or not, and enable itself
if the disk is encrypted, and disable itself when the disk is not
encrypted. If you use this mode, you can read and write data from
normal and encrypted disks without any special user actions.
You can optionally specify the drive for which this option applies.
2.3.6. write (w)
This option is almost the same as option 'auto', except for one
thing: you can not write data to 'normal' disks! 'Normal' disks can
be read however. There are no restrictions on the use of encrypted
disks.
You can optionally specify the drive for which this option applies.
2.3.7. query (q)
If you use option 'auto' or 'write' it is not possible to find out
whether a disk is encrypted or not because TbGarble decrypts any
encrypted disk when you try to read data. Option 'query' can be
used to find out whether a disk is encrypted.
2.4. Examples:
C:\utils\TbGarble
or:
Device=C:\utils\TbGarble.Exe
TbGarble is installed with the 'auto' mode for both diskette
drives.
C:\utils\TbGarble on=B
TbGarble uses the 'auto' mode for drive A, but forces drive B to be
encrypted.
2.5. Creating garbled disks
In the 'auto' and 'off' mode, TbGarble will make a disk normal when
the disk is being formatted.
To create an encrypted diskette, you must specify the 'on' or
'write' option of TbGarble before formatting the disk.
After the disk has been formatted, you can write (copy) data to it
if TbGarble option 'on', 'write' or 'auto' is used.
2.6. The encryption key
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Thunderbyte auto disk (de)cryptor. (C) 1992 Thunderbyte B.V.
All unregistered versions of TbGarble use the same encryption key.
Registered versions of TbGarble will use a random defined key in
the TBAV.KEY file.
If you are a registered user, nobody can determine your encryption
key if they do not have access to your TBAV.KEY file. Make sure to
keep a backup of your TBAV.KEY file! If you lose your key, there
is no way to read your encrypted disks anymore!!!
2.7. The hardware garbler
The main disadvantage of TbGarble is that it can be removed from
the Config.Sys, and then the protection is gone.
TbGarble is also available as an add-on card for the PC with AT and
MCA buses. The Garbler can no longer be disabled, and is
immediately active. It is even possible to boot from encrypted
disks!
If you have the hardware card, you can still use TbGarble.Exe to
configure the hardware garbler. Before the TbGarble invocation,
dipswitches on the card determine the behavior of the Garbler.
Of course the card can also be configured to deny user
configuration.
Consult the accompanying documentation of the card for more
information.
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