Liren Large Software Subsidy 16/16.iso/t/t246/1.img/OBLIT.DOC

Text File | 1993-07-02 | 9.5 KB | 208 lines

                        OBLIT.DOC - v1.2
                  (C)1993 Tolgathian Software

OVERVIEW

Hello!

 This program is for you security minded people out there,
especially those using encryption. It will completely and
irretrievably destroy the contents of ANY file. It then
deletes it for good measure.

 Just in case you did not know this, when you delete a file, like
the plain text of a message you just encrypted, all MS-DOS does is
remove it from the File Allocation Table. The file is still there,
but it is just removed from the MS-DOS "do not use this space" list.
It can easily be undeleted with the DOS command UNDELETE. If someone
was to undelete a file after you have used OBLIT on it, however, it
will be completely full of garbage when they try and look at it.
Even sophisticated magnetic signature equipment will have a hard
time reconstructing the file, because OBLIT writes over the file
with three patterns five times each. This is a total of fifteen
writes. Good luck to the snoop.


IMPORTANT NOTES ON SECURITY

 Something you need to be aware of, is that many (if not all)
word processors and text editors make "backup" copies of the document
you are working on. These files normally have a BAK extension to
the file. Make sure that if you are trying to OBLIT a file that
you OBLIT other copies of it as well! For example, suppose I have
a file called PERSONAL.TXT and I edit it with my favorite text
editor. Every time I do so, the editor makes a PERSONAL.BAK copy of
the file. If I decide to OBLIT the file PERSONAL.TXT, I must also
OBLIT the file PERSONAL.BAK, otherwise someone could read it.
A simple way to look for multiple copies of a file in a directory
is to do a DIR command on the file, without the extension:
DIR PERSONAL will reveal the files PERSONAL.TXT, PERSONAL.BAK,
and PERSONAL.DOC. You can also specify any extension by using
a * wilcard. DIR PERSONAL.* will reveal the same files above.

 Another word about word processors. Many of them make periodic
saves to a temporary file while you are editing. This way, if
power fails in the middle of what you are doing, the program can
reconstruct your document up to the last time it saved it. This
is not good for security. The program does not use your filename,
it uses a randomly generated or preset one. If at all possible,
TURN THIS FEATURE OFF WHEN EDITING SENSITIVE INFORMATION!!
Otherwise, you can OBLIT and encrypt everything in sight, but a
snoop only has to "undelete" the temporary file(s) they find
and read them instead. If you can not turn this off, find out
from the manual or the manufacturer what the temporary filename
is. When you are through editing, exit the program, use the
MS-DOS undelete function to bring it back, and then OBLIT it.

 I would recommend using a plain vanilla text-editor and not a
word processor for sensitive text. They tend to not outsmart you
and are very straight forward. Usually they only make *.BAK copies
of your work, and who needs Times Roman 24 point fonts in
confidential information anyway?

 One of the keys to good security is Keep It Simple Stupid.
The only thing that needs to be complicated is an encryption
algorithm. The simpler things are, the easier they are to control.



 For the utmost in security, a good encryption program will lock
up your data from intruders and snoops. Depending on the stuff
you are trying to hide, you need to be sure the encryption is
strong against a concerted cryptanalytic attack. Unfortunately,
most commercial software is either weak because the programmer is
not well versed in cryptography, or it is based on a U.S. Government
encryption standard called DES. The Government does not rely on
the DES for military applications. This should warn you that if
you are trying to hide from them that you should NOT use this
kind of encryption. One of the best programs for encryption is
Pretty Good Privacy (PGP) by Phil Zimmerman. This program is
currently in version 2.2, and is available across many BBS systems.
Phil provides a pretty good overview of encryption and security,
and so even if you are not interested in using his program, you
should obtain a copy just to read the documentation he includes.
Chances are after reading it, you will use PGP. The program is excellent.

 If you really need to be extra cautious, you might need to
purchase a bulk degausser. These are basically large AC electro-
magnets. By moving the floppy disk (or hard disk) through their
very powerfull magnetic field, you effectively erase everything
all at once.  Or, if you don't mind losing floppies, you could simply
burn them instead. Hard drives are harder to destroy, so a
degausser is your best bet. I would still OBLIT things first.


= Legalus Stayvus Offus ad Legalus Nauseum =

Tolgathian Software hereby places this program and it's related
documentation into the Public Domain as long as this document file
remains with it and both remain unaltered. It may be archived and
freely distributed across, through and in any medium. It may be
distributed by commercial operations as long as no charge is made
for the software - only a reasonable medium/processing charge may
apply. Tolgathian Software and anyone related to it (i.e.: it's
employees, members, and owners) provide this software as is, and
no gaurantee is made for it's proper operation and fitness for any
purpose. The user understands and agrees that the user will not
hold Tolgathian Software, it's employees, members, or owners
responsible for any direct, incidental, related, consequential,
or otherwise remotely conceived or connected damages as the result
of it's use or misuse. Because of the nature of computers in general
and the power/resources wielded by the government and large
corporations in particular, the user understands that no gaurantee
is made that this program will protect information from disclosure.
The only real secret is the one that only you know.

Sorry to bore you with that stuff, but good heavens! People will
sue the Mayor if they fall and hurt themselves while doing a
handstand on a skateboard going downhill on a gravel sidewalk
backwards with no helmet at rush-hour blindfolded. And some fool
lawyer that should know better will help them do it!
("Doctor! It hurts when I do this!" "Well, don't do it."
 "You Quack! I'm gonna sue you from here 'til Sunday!")


= Internalus Workus =

 This is how it works. OBLIT looks at the file and sees how many
bytes long it is. It then writes three different byte-long bit
patterns over each byte in the file, for the length of the file.
These patterns are:

                11111111
                00000000
                <random>

It does this same operation 5 times, just to make sure that any
latent magnetic signature of the original file is destroyed as
far as possible. With each pass, a different psuedo-random byte
is written. The random number generator is re-seeded with each
pass. (The seed is based on the clock ticks inside your machine.)
As you can see, the last pattern is all random. This is what the
file is left containing before being deleted.

 Be sure that you want to destroy the file before you do so, as
unlike a simple MS-DOS delete, there is NO way for you to bring
this file back from an OBLIT. It is gone. Period.


INSTALLATION

 Copy the OBLIT.COM file from wherever it is now to one of the
directories in your PATH. Some people put utilities in their
DOS directory, others like me put them in a UTILS directory.
If the program is in your PATH, you will be able to use it from
anywhere.
 If this is all strange to you and you do not know what I am
talking about, try this: Suppose the program OBLIT.COM is on a
disk in the A: drive. Suppose you want to copy it to your C:
drive, to a directory called DOS. This is what you would type
at any DOS prompt:

        COPY A:\OBLIT.COM C:\DOS

 This should do the trick. Still stuck? Ask a friend or read the
DOS manual where it talks about directories and such.


USAGE:
        OBLIT [?]

        Items in brackets are optional.
        ?  -include this on the command line for the
            help screen.

OBLIT warns you what it does, and asks for a filename. You must
enter a filename, and the filename can include a path. Suppose I
wanted to OBLIT a file called PERSONAL.TXT on the B: drive in the
directory DOCS. I would type:   B:\DOCS\PERSONAL.TXT

Note that OBLIT doe NOT accept wildcards (*,?) in the filename.
This protects against accidental catastrophic obliterations.
You must run OBLIT for each file you want obliterated.

Note that you can not OBLIT an already deleted file. You must
undelete it first and THEN OBLIT it. You don't know how to use
the undelete command? Look it up in your DOS manual.

Next, OBLIT warns you again that the file will be GONE when it
is done. You must type YES in capital letters for OBLIT to work.
Any other response will abort the operation with an OK message.
If you type YES, then seconds later you can rest assured the file
is absolutely obliterated. An OBLIT takes longer than a delete.
Be patient. On my 386-40 a 70Kbyte file takes about 70 seconds
to obliterate on the hard drive (I have an old slow drive), and
takes 8 minutes on a floppy.


AN OBLITed FILE IS HISTORY! GONE! KAPUT! NICHT! NOT! VOID! NULL!
BE ABSOLUTELY CERTAIN YOU NEVER WANT THE FILE AGAIN. THERE IS
NO TURNING BACK FROM AN OBLIT! REPEAT AFTER ME: "OBLIT IS PERMANENT
LIKE DEATH AND TAXES, THERE IS NO RECOVERY POSSIBLE!"


Good Luck!


Tolgathian Software - purveyors of fine no frills utilities.