From: robichau@lambda.msfc.nasa.gov (Paul Robichaux)
Date: Thu, 1 Apr 93 08:18:16 PST
To: cypherpunks@toad.com
Subject: PHRACK: Article from PHRACK 42 on encryption
Message-ID: <9304011902.AA26513@lambda.msfc.nasa.gov>
MIME-Version: 1.0
Content-Type: text/plain


Attached is an article from PHRACK 42 written by "The Racketeer."

Exposing factual errors and flaws in reasoning is left as an exercise
for the reader.

-Paul



              ###################################################
              # The Paranoid Schizophrenics Guide to Encryption #
              #   (or How to Avoid Getting Tapped and Raided)   #
              ###################################################

                        Written by The Racketeer of
                            The /-/ellfire Club


        The purpose of this file is to explain the why and the how of Data
Encryption, with a brief description of the future of computer security,
TEMPEST.

        At the time of this issue's release, two of the more modern software
packages use encryption methods covered in this article, so exercise some of
your neurons and check into newer releases if they are available.  Methods
described in this file use PGP, covering an implementation of Phil Zimmermann's
RSA variant, and the MDC and IDEA conventional encryption techniques by using
PGP and HPACK.

                              --------------------
                              WHY DATA ENCRYPTION?
                              --------------------

        This isn't exactly the typical topic discussed by me in Phrack.
However, the importance of knowing encryption is necessary when dealing with
any quasi-legal computer activity.  I was planning on starting my series on
hacking Novell Networks (so non-Internet users can have something to do), but
recent events have caused me to change my mind and, instead of showing people
how to get into more trouble (well, okay, there is plenty of that in this file
too, since you're going to be working with contraband software), I've opted
instead to show people how to protect themselves from the long arm of the Law.

        Why all this concern?

        Relatively recently, The Masters of Deception (MoD) were raided by
various federal agencies and were accused of several crimes.  The crimes they
did commit will doubtlessly cause more mandates, making the already
too-outrageous penalties even worse.

        "So?" you might ask.  The MoD weren't exactly friends of mine.  In fact,
quite the contrary.  But unlike many of the hackers whom I dealt with in the
"final days" prior to their arrest, I bitterly protested any action against the
MoD.  Admittedly, I followed the episode from the beginning to the end, and the
moral arguments were enough to rip the "Hacker World" to pieces.  But these
moral issues are done, the past behind most of us.  It is now time to examine
the aftermath of the bust.

        According to the officials in charge of the investigation against MoD
members, telephone taps were used to gain evidence against members
successfully.  All data going in and out of their house was monitored and all
voice communications were monitored, especially between members.

        So, how do you make a line secure?  The party line answer is use of
effective encryption methods.

        Federal investigative agencies are currently pushing for more
technological research into the issue of computer security.  All of the popular
techniques which are being used by hackers today are being used by the
government's R&D departments.

        Over the course of the last 5 years, I've watched as the U.S.
Government went from a task force of nearly nil all the way to a powerful
marauder.  Their mission?  Unclear.  Regardless, the research being
accomplished by federally-funded projects dealing with the issues of computer
security are escalating.  I've personally joined and examined many such
conferences and have carefully examined the issues.  Many of these issues will
become future Phrack articles which I'll write.  Others, such as limited-life
semiconductors and deliberate telephone line noise sabotage caused by ACK
packet detections in order to drive telecommunication costs higher, are sadly
unpreventable problems of the future which won't be cured by simple awareness
of the problem.

        They have different names -- Computer Emergency Response Team (CERT),
Computer Assisted Security Investigative Analysis Tool (FBI's CASIAT), the
Secret Service's Computer Fraud Division, or the National Computer Security
Center (NSA's NCSC).  Scores of other groups exist for every network, even
every operating system.  Their goal isn't necessarily to catch hackers; their
goal is to acquire information about the act of hacking itself until it is no
longer is a problem.  Encryption stands in the way.

        Computer Security is literally so VAST a concept that, once a person
awakens to low-level computer mechanics, it becomes nearly impossible to
prevent that person from gaining unauthorized access to machines.  This is
somewhat contradictory to the "it's all social engineering" concept which we
have been hearing about on Nightline and in the papers.  If you can't snag them
one way though, you can get them another -- the fact is that computers are
still too damn vulnerable these days to traditional hacking techniques.

        Because of the ease of breaking through security, it becomes very
difficult to actually create an effective way to protect yourself from any form
of computer hacking.  Look at piracy:  they've tried every trick in the book to
protect software and, so far, the only success they have had was writing
software that sucked so much nobody wanted a copy.

        Furthermore, totally non-CPU related attacks are taking place.  The
passing of Anti-TEMPEST Protection Laws which prevent homes from owning
computers that don't give off RF emissions has made it possible for any Joe
with a few semesters of electrical engineering knowledge to rig together a
device that can read what's on your computer monitor.

     Therefore:

     Q:  How does a person protect their own computer from getting hacked?

     A:  You pretty much can't.

        I've memorized so many ways to bypass computer security that I can
rattle them off in pyramid levels.  If a computer is not even connected to a
network or phone line, people can watch every keystroke typed and everything
displayed on the screen.

        Why aren't the Fedz using these techniques RIGHT NOW?

        I can't say they are not.  However, a little research into TEMPEST
technology resulted in a pretty blunt fact:

        There are too many computer components to scan accurately.  Not the
monitor, oh no!  You're pretty much fucked there.  But accessories for input
and output, such as printers, sound cards, scanners, disk drives, and so
forth...the possibility of parallel CPU TEMPEST technology exists, but there are
more CPU types than any mobile unit could possibly use accurately.

        Keyboards are currently manufactured by IBM, Compaq, Dell, Northgate,
Mitsuma (bleah), Fujitsu, Gateway, Focus, Chichony, Omni, Tandy, Apple, Sun,
Packard-Bell (may they rot in hell), Next, Prime, Digital, Unisys, Sony,
Hewlett-Packard, AT&T, and a scattering of hundreds of lesser companies.  Each
of these keyboards have custom models, programmable models, 100+ key and < 100
key models, different connectors, different interpreters, and different levels
of cable shielding.

        For the IBM compatible alone, patents are owned on multiple keyboard
pin connectors, such as those for OS/2 and Tandy, as well as the fact that the
ISA chipsets are nearly as diverse as the hundreds of manufacturers of
motherboards.  Because of lowest-bid practices, there can be no certainty of
any particular connection -- especially when you are trying to monitor a
computer you've never actually seen!

        In short -- it costs too much for the TEMPEST device to be mobile and
to be able to detect keystrokes from a "standard" keyboard, mostly because
keyboards aren't "standard" enough!  In fact, the only real standard which I
can tell exists on regular computers is the fact that monitors still use good
old CRT technology.

        Arguments against this include the fact that most of the available PC
computers use standard DIN connectors which means that MOST of the keyboards
could be examined.  Furthermore, these keyboards are traditionally serial
connections using highly vulnerable wire (see Appendix B).

        Once again, I raise the defense that keyboard cables are traditionally
the most heavily shielded (mine is nearly 1/4 inch thick) and therefore falls
back on the question of how accurate a TEMPEST device which is portable can be,
and if it is cost effective enough to use against hackers.  Further viewpoints
and TEMPEST overview can be seen in Appendix B.

        As a result, we have opened up the possibility for protection from
outside interference for our computer systems.  Because any DECENT encryption
program doesn't echo the password to your screen, a typical encryption program
could provide reasonable security to your machine.  How reasonable?

        If you have 9 pirated programs installed on your computer at a given
time and you were raided by some law enforcement holes, you would not be
labeled at a felon.  Instead, it wouldn't even be worth their time to even raid
you.  If you have 9 pirated programs installed on your computer, had 200
pirated programs encrypted in a disk box, and you were raided, you would have
to be charged with possession of 9 pirated programs (unless you did something
stupid, like write "Pirated Ultima" or something on the label).

        We all suspected encryption was the right thing to do, but what about
encryption itself?  How secure IS encryption?

        If you think that the world of the Hackers is deeply shrouded with
extreme prejudice, I bet you can't wait to talk with crypto-analysts.  These
people are traditionally the biggest bunch of holes I've ever laid eyes on.  In
their mind, people have been debating the concepts of encryption since the dawn
of time, and if you come up with a totally new method of data encryption, -YOU
ARE INSULTING EVERYONE WHO HAS EVER DONE ENCRYPTION-, mostly by saying "Oh, I
just came up with this idea for an encryption which might be the best one yet"
when people have dedicated all their lives to designing and breaking encryption
techniques -- so what makes you think you're so fucking bright?

        Anyway, crypto-(anal)ysts tend to take most comments as veiled insults,
and are easily terribly offended.  Well, make no mistake, if I wanted to insult
these people, I'd do it.  I've already done it.  I'll continue to do it.  And I
won't thinly veil it with good manners, either.

        The field of Crypto-analysis has traditionally had a mathematical
emphasis.  The Beal Cipher and the German Enigma Cipher are some of the more
popular views of the field.  Ever since World War 2, people have spent time
researching how technology was going to affect the future of data encryption.

        If the United States went to war with some other country, they'd have a
strong advantage if they knew the orders of the opposing side before they were
carried out.  Using spies and wire taps, they can gain encrypted data referred
to as Ciphertext.  They hand the information over to groups that deal with
encryption such as the NSA and the CIA, and they attempt to decode the
information before the encrypted information is too old to be of any use.

        The future of Computer Criminology rests in the same ways.  The
deadline on white collar crimes is defaulted to about 3-4 years, which is
called the Statute of Limitations.  Once a file is obtained which is encrypted,
it becomes a task to decrypt it within the statute's time.

        As most crypto-analysts would agree, the cost in man-hours as well as
supercomputer time would make it unfeasible to enforce brute force decryption
techniques of random encryption methods.  As a result of this, government
regulation stepped in.

        The National Security Agency (referred to as "Spooks" by the relatively
famous tormenter of KGB-paid-off hackers, Cliff Stoll, which is probably the
only thing he's ever said which makes me think he could be a real human being)
released the DES -- Data Encryption Standard.  This encryption method was
basically solid and took a long time to crack, which was also the Catch-22.

        DES wasn't uncrackable, it was just that it took "an unreasonable
length of time to crack."  The attack against the word "unreasonable" keeps
getting stronger and stronger.  While DES originated on Honeywell and DEC PDPs,
it was rumored that they'd networked enough computers together to break a
typical DES encrypted file.  Now that we have better computers and the cost
requirements for high-speed workstations are even less, I believe that even if
they overestimated "unreasonable" a hundredfold, they'd be in the "reasonable"
levels now.

To explain how fast DES runs these days...

        I personally wrote a password cracker for DES which was arguably the
very first true high-speed cracker.  It used the German "Ultra-Fast Crypt"
version of the DES algorithm, which happened to contain a static variable used
to hold part of the previous attempt at encrypting the password, called the
salt.  By making sure the system wouldn't resalt on every password attempt, I
was able to guess passwords out of a dictionary at the rate of 400+ words per
second on a 386-25 (other methods at that time were going at about 30 per
second).  As I understand it now, levels at 500+ for the same CPU have been
achieved.

        Now this means I can go through an entire dictionary in about five
minutes on a DES-encrypted segment.  The NSA has REAL cash and some of the
finest mathematicians in the world, so if they wanted to gain some really
decent speed on encryption, DES fits the ideal for parallel programming.
Splitting a DES segment across a hundred CPUs, each relatively modern, they
could crank out terraflops of speed.  They'd probably be able to crack the code
within a few days if they wanted to.

        Ten years from now, they could do it in a few seconds.

        Of course, the proper way to circumnavigate DES encryption is to locate
and discover a more reliable, less popular method.  Because the U.S. Government
regulates it, it doesn't mean it's the best.  In fact, it means it's the
fucking lamest thing they could sweeten up and hope the public swallows it!
The last attempt the NSA made at regulating a standard dealing with encryption,
they got roasted.

        I'm somewhat convinced that the NSA is against personal security, and
from all the press they give, they don't WANT anyone to have personal security.
Neither does the Media for that matter.

        Because of lamers in the "Biblical Injustice Grievance Group of
Opposing Terrible Sacrilege" (or BIGGOTS) who think that if you violate a LAW
you're going to Hell (see APPENDIX C for my viewpoint of these people) and who
will have convinced Congress to pass ease-of-use wire taps on telephone lines
and networks so that they can monitor casual connections without search
warrants, encryption will be mandatory if you want any privacy at all.

        And to quote Phil Zimmermann, "If privacy is outlawed, only the
outlaws will have privacy."

        Therefore, encryption methods that we must use should be gathered into
very solid categories which do NOT have endorsement of the NSA and also have
usefulness in technique.

HOW TO USE DECENT ENCRYPTION:

(First, go to APPENDIX D, and get yourself a copy of PGP, latest version.)

        First of all, PGP is contraband software, presumably illegal to use in
the United States because of a patent infringement it allegedly carries.  The
patent infringement is the usage of a variant of the RSA encryption algorithm.
Can you patent an algorithm?  By definition, you cannot patent an idea, just a
product -- like source code.  Yet, the patent exists to be true until proven
false.  More examples of how people in the crypto-analyst field can be assholes.

        Anyway, Phil's Pretty Good Software, creators of PGP, were sued and all
rights to PGP were forfeited in the United States of America.  Here comes the
violation of the SECOND law, illegal exportation of a data encryption outside
of the United States of America.  Phil distributed his encryption techniques
outside the USA, which is against the law as well.  Even though Mr. Zimmermann
doesn't do any work with PGP, because he freely gave his source code to others,
people in countries besides the United States are constantly updating and
improving the PGP package.

        PGP handles two very important methods of encryption -- conventional
and public key.  These are both very important to understand because they
protect against completely different things.

                            -----------------------
                            CONVENTIONAL ENCRYPTION
                            -----------------------

        Conventional encryption techniques are easiest to understand.  You
supply a password and the password you enter encrypts a file or some other sort
of data.  By re-entering the password, it allows you to recreate the original
data.

        Simple enough concept, just don't give the password to someone you
don't trust.  If you give the password to the wrong person, your whole business
is in jeopardy.  Of course, that goes with just about anything you consider
important.

        There are doubtlessly many "secure enough" ciphers which exist right
now.  Unfortunately, the availability of these methods are somewhat slim
because of exportation laws.  The "major" encryption programs which I believe
are worth talking about here are maintained by people foreign to the USA.

        The two methods of "conventional" encryption are at least not DES,
which qualifies them as okay in my book.  This doesn't mean they are impossible
to break, but they don't have certain DES limitations which I know exist, such
as 8 character password maximum.  The methods are:  MDC, as available in the
package HPACK; and IDEA, as available in Pretty Good Privacy.

        Once you've installed PGP, we can start by practicing encrypting
some typical files on your PC.  To conventionally encrypt your AUTOEXEC.BAT
file (it won't delete the file after encryption), use the following command:

C:\> pgp -c autoexec.bat
Pretty Good Privacy 2.1 - Public-key encryption for the masses.
(c) 1990-1992 Philip Zimmermann, Phil's Pretty Good Software. 6 Dec 92
Date: 1993/01/19 03:06 GMT

You need a pass phrase to encrypt the file.
Enter pass phrase:                                      { Password not echoed }
Enter same pass phrase again: Just a moment....
Ciphertext file: autoexec.pgp

C:\> dir

 Volume in drive C is RACK'S
 Directory of  c:\autoexec.pgp

autoexec.pgp      330 1-18-93  21:05

        330 bytes in 1 file(s)          8,192 bytes allocated
  52,527,104 bytes free

        PGP will compress the file before encrypting it.  I'd say this is a
vulnerability to the encryption on the basis that the file contains a ZIP file
signature which could conceivably make the overall encryption less secure.
Although no reports have been made of someone breaking PGP this way, I'd feel
more comfortable with the ZIP features turned off.  This is somewhat contrary
to the fact that redundancy checking is another way of breaking ciphertext.
However, it isn't as reliable as checking a ZIP signature.

        Although PGP will doubtlessly become the more popular of the two
programs, HPACK's encryption "strength" is that by being less popular, it will
probably not be as heavily researched as PGP's methods will be.  Of course, by
following PGP, new methods of encryption will doubtlessly be added as the
program is improved.

        Here is how you'd go about encrypting an entire file using the HPACK
program using the MDC "conventional" encryption:

C:\> hpack A -C secret.hpk secret.txt
HPACK - The multi-system archiver Version 0.78a0 (shareware version)
For Amiga, Archimedes, Macintosh, MSDOS, OS/2, and UNIX
Copyright (c) Peter Gutmann 1989 - 1992.  Release date: 1 Sept 1992

Archive is 'SECRET.HPK'

Please enter password (8..80 characters):
Reenter password to confirm:
Adding SECRET  .TXT

Done

        Anyway, I don't personally think HPACK will ever become truly popular
for any reason besides its encryption capabilities.  ZIP has been ported to an
amazing number of platforms, in which lies ZIP's encryption weakness.  If you
think ZIP is safe, remember that you need to prevent the possibility of four
years of attempted password cracking in order to beat the Statutes of
Limitations:

        Here is the introduction to ZIPCRACK, and what it had to say about how
easy it is to break through this barrier:

(Taken from ZIPCRACK.DOC)
-----
     ZIPCRACK is a program designed to demonstrate how easy it is to find
passwords on files created with PKZIP.  The approach used is a fast,
brute-force attack, capable of scanning thousands of passwords per second
(5-6000 on an 80386-33).  While there is currently no known way to decrypt
PKZIP's files without first locating the correct password, the probability that
a particular ZIP's password can be found in a billion-word search (which takes
about a day on a fast '486) is high enough that anyone using the encryption
included in PKZIP 1.10 should be cautious (note:  as of this writing, PKZIP
version 2.00 has not been released, so it is not yet known whether future
versions of PKZIP will use an improved encryption algorithm).  The author's
primary purpose in releasing this program is to encourage improvements in ZIP
security.  The intended goal is NOT to make it easy for every computer user to
break into any ZIP, so no effort has been made to make the program
user-friendly.
----- End Blurb

        Likewise, WordPerfect is even more vulnerable.  I've caught a copy of
WordPerfect Crack out on the Internet and here is what it has to say about
WordPerfect's impossible-to-break methods:

(Taken from WPCRACK.DOC:)
-----
WordPerfect's manual claims that "You can protect or lock your documents with a
password so that no one will be able to retrieve or print the file without
knowing the password - not even you," and "If you forget the password, there is
absolutely no way to retrieve the document."  [1]

Pretty impressive!  Actually, you could crack the password of a Word Perfect
5.x file on a 8 1/2" x 11" sheet of paper, it's so simple.  If you are counting
on your files being safe, they are NOT.  Bennet [2] originally discovered how
the file was encrypted, and Bergen and Caelli [3] determined further
information regarding version 5.x.  I have taken these papers, extended them,
and written some programs to extract the password from the file.
----- End Blurb

                             ---------------------
                             PUBLIC KEY ENCRYPTION
                             ---------------------

        Back to the Masters of Deception analogy -- they were telephone
tapped.  Conventional encryption is good for home use, because only one person
could possibly know the password.  But what happens when you want to transmit
the encrypted data by telephone?  If the Secret Service is listening in on your
phone calls, you can't tell the password to the person that you want to send
the encrypted information to.  The SS will grab the password every single time.

        Enter Public-Key encryption!   The concepts behind Public-Key are very
in-depth compared to conventional encryption.  The idea here is that passwords
are not exchanged; instead a "key" which tells HOW to encrypt the file for the
other person is given to them.  This is called the Public Key.

        You retain the PRIVATE key and the PASSWORD.  They tell you how to
decrypt the file that someone sent you.  There is no "straight" path between
the Public Key and the Private Key, so just because someone HAS the public key,
it doesn't mean they can produce either your Secret Key or Password.  All it
means is that if they encrypt the file using the Public Key, you will be able
to decrypt it.  Furthermore, because of one-way encryption methods, the output
your Public Key produces is original each time, and therefore, you can't
decrypt the information you encrypted with the Public Key -- even if you
encrypted it yourself!

        Therefore, you can freely give out your own Public Key to anyone you
want, and any information you receive, tapped or not, won't make a difference.
As a result, you can trade anything you want and not worry about telephone
taps!  This technique supposedly is being used to defend the United States'
Nuclear Arsenal, if you disbelieve this is secure.

        I've actually talked with some of the makers of the RSA "Public-Key"
algorithm, and, albeit they are quite brilliant individuals, I'm somewhat
miffed at their lack of enthusiasm for aiding the public in getting a hold of
tools to use Public Key.  As a result, they are about to get railroaded by
people choosing to use PGP in preference to squat.

        Okay, maybe they don't have "squat" available.  In fact, they have a
totally free package with source code available to the USA public (no
exportation of code) which people can use called RSAREF.  Appendix E explains
more about why I'm not suggesting you use this package, and also how to obtain
it so you can see for yourself.

        Now that we know the basic concepts of Public-Key, let's go ahead and
create the basics for effective tap-proof communications.

Generation of your own secret key (comments in {}s):

C:\> pgp -kg               {  Command used to activate PGP for key generation }
Pretty Good Privacy 2.1 - Public-key encryption for the masses.
(c) 1990-1992 Philip Zimmermann, Phil's Pretty Good Software. 6 Dec 92
Date: 1993/01/18 19:53 GMT

Pick your RSA key size:
        1)       384 bits- Casual grade, fast but less secure
        2)       512 bits- Commercial grade, medium speed, good security
        3)      1024 bits- Military grade, very slow, highest security
Choose 1, 2, or 3, or enter desired number of bits: 3  {DAMN STRAIGHT MILITARY}

Generating an RSA key with a 1024-bit modulus...
You need a user ID for your public key.  The desired form for this
user ID is your name, followed by your E-mail address enclosed in
<angle brackets>, if you have an E-mail address.
For example:  John Q. Smith <12345.6789@compuserve.com>

Enter a user ID for your public key:
The Racketeer <rack@lycaeum.hfc.com>

You need a pass phrase to protect your RSA secret key.
Your pass phrase can be any sentence or phrase and may have many
words, spaces, punctuation, or any other printable characters.
Enter pass phrase:                                     { Not echoed to screen }
Enter same pass phrase again:                          {  "    "    "    "    }
Note that key generation is a VERY lengthy process.

We need to generate 105 random bytes.  This is done by measuring the
time intervals between your keystrokes.  Please enter some text on your
keyboard, at least 210 nonrepeating keystrokes, until you hear the beep:
1 .*                                                             { decrements }
-Enough, thank you.
..................................................++++ ........++++
Key generation completed.

        It took a 33-386DX a grand total of about 10 minutes to make the key.
Now that it has been generated, it has been placed in your key ring.  We can
examine the key ring using the following command:

C:\> pgp -kv
Pretty Good Privacy 2.1 - Public-key encryption for the masses.
(c) 1990-1992 Philip Zimmermann, Phil's Pretty Good Software. 6 Dec 92
Date: 1993/01/18 20:19 GMT

Key ring: 'c:\pgp\pubring.pgp'
Type bits/keyID   Date       User ID
pub  1024/7C8C3D  1993/01/18 The Racketeer <rack@lycaeum.hfc.com>
1 key(s) examined.

        We've now got a viable keyring with your own keys.  Now, you need to
extract your Public Key so that you can have other people encrypt shit and have
it sent to you.  In order to do this, you need to be able to mail it to them.
Therefore, you need to extract it in ASCII format.  This is done by the
following:

C:\> pgp -kxa "The Racketeer <rack@lycaeum.hfc.com>"
Pretty Good Privacy 2.1 - Public-key encryption for the masses
(c) 1990-1992 Philip Zimmermann, Phil's Pretty Good Software. 6 Dec 92
Date: 1993/01/18 20:56 GMT

Extracting from key ring:  'c:\pgp\pubring.pgp', userid "The Racketeer
<rack@lycaeum.hfc.com>".

Key for user ID: The Racketeer <rack@lycaeum.hfc.com>
1024-bit key, Key ID 0C975F, created 1993/01/18

Extract the above key into which file? rackkey

Transport armor file: rackkey.asc

Key extracted to file 'rackkey.asc'.

        Done.  The end result of the key is a file which contains:

-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: 2.1

mQCNAisuyi4AAAEEAN+cY6nUU+VIhYOqBfcc12rEMph+A7iadUi8xQJ00ANvp/iF
+ugZ+GP2ZnzA0fob9cG/MVbh+iiz3g+nbS+ZljD2uK4VyxZfu5alsbCBFbJ6Oa8K
/c/e19lzaksSlTcqTMQEae60JUkrHWpnxQMM3IqSnh3D+SbsmLBs4pFrfIw9AAUR
tCRUaGUgUmFja2V0ZWVyIDxyYWNrQGx5Y2FldW0uaGZjLmNvbT4=
=6rFE
-----END PGP PUBLIC KEY BLOCK-----

        This can be tagged to the bottom of whatever E-Mail message you want to
send or whatever.  This key can added to someone else's public key ring and
thereby used to encrypt information so that it can be sent to you.  Most people
who use this on USENET add it onto their signature files so that it is
automatically posted on their messages.

        Let's assume someone else wanted to communicate with you.  As a result,
they sent you their own Public Key:

-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: 2.1

mQA9AitgcOsAAAEBgMlGLWl8rub0Ulzv3wpxI5OFLRkx3UcGCGsi/y/Qg7nR8dwI
owUy65l9XZsp0MUnFQAFEbQlT25lIER1bWIgUHVkIDwxRHVtUHVkQG1haWxydXMu
Yml0bmV0Pg==
=FZBm
-----END PGP PUBLIC KEY BLOCK-----

        Notice this guy, Mr. One Dumb Pud, used a smaller key size than you
did.  This shouldn't make any difference because PGP detects this
automatically.  Let's now add the schlep onto your key ring.

C:\> pgp -ka dumbpud.asc
Pretty Good Privacy 2.1 - Public-key encryption for the masses.
(c) 1990-1992 Philip Zimmermann, Phil's Pretty Good Software. 6 Dec 92
Date: 1993/01/22 22:17 GMT

Key ring: 'c:\pgp\pubring.$01'
Type bits/keyID   Date       User ID
pub   384/C52715  1993/01/22 One Dumb Pud <1DumPud@mailrus.bitnet>

New key ID: C52715

Keyfile contains:
   1 new key(s)
Adding key ID C52715 from file 'dumbpud.asc' to key ring 'c:\pgp\pubring.pgp'.

Key for user ID: One Dumb Pud <1DumPud@mailrus.bitnet>
384-bit key, Key ID C52715, crated 1993/01/22
This key/userID associate is not certified.

Do you want to certify this key yourself (y/N)?  n {We'll deal with this later}

        Okay, now we have the guy on our key ring.  Let's go ahead and encrypt
a file for the guy.  How about having the honor of an unedited copy of this
file?

C:\> pgp -e encrypt One                     {PGP has automatic name completion}
Pretty Good Privacy 2.1 - Public-key encryption for the masses.
(c) 1990-1992 Philip Zimmermann, Phil's Pretty Good Software. 6 Dec 92
Date: 1993/01/22 22:24 GMT


Recipient's public key will be used to encrypt.
Key for user ID: One Dumb Pud <1DumPud@mailrus.bitnet>
384-bit key, Key ID C52715, created 1993/01/22

WARNING:  Because this public key is not certified with a trusted
signature, it is not known with high confidence that this public key
actually belongs to: "One Dumb Pud <1DumPud@mailrus.bitnet>".

Are you sure you want to use this public key (y/N)? y

-- 
Paul Robichaux, KD4JZG                | May explode if disposed of improperly.
NTI Mission Software Development Div. | RIPEM key on request.