Revised 2 January 1999
Disclaimer: some of this information may be outdated or otherwise inaccurate. Use it at your own risk.
The master copy of this FAQ is at http://www.cryptography.org/getpgp.htm (and at http://www.cryptography.org/getpgp.txt for the text-only version) .
The official (much more complete) PGP FAQ is available at: http://www.cam.ac.uk.pgp.net/pgpnet/pgp-faq/
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If you are in the USA or Canada, try one of these URLs:
MANY BBS carry PGP. The following carry recent versions of PGP and allow free downloads of PGP.
If you have access to email, but not to ftp, send a message saying "help" to email@example.com or firstname.lastname@example.org
The PGP-Users Mailing List home page at http://pgp.rivertown.net contains many PGP related resources, including resources on privacy, anonymous remailers, and other related fields. The PGP-Users list archives are also linked to the page as is an HTML version of the PGP-FAQ (may not be the most recent), the PGP documentation, resources for MacPGP, links to another mailing list dedicated to PGPfone (which includes one of its authors, Will Price) and the one of a kind, PGPfone Registry, where PGPfone users who would like to test PGPfone with each other can leave messages in a browsable data base to let others find them to connect with each other.
Yes. You can get the official PGP documentation in several languages at http://www.pgpi.com. German documentation is at http://www.geocities.com/Athens/1802/ and French is at http://www.geocities.com/SiliconValley/Bay/9648/.
PGP 5.0 introduces some new algorithms for both public key and conventional encryption. These changes are good from both technical (security & efficiency) and political (patent) standpoints. With the death of the Diffie-Hellman key exchange patent, the freeware PGP new algorithms are 100% free of patent problems, and free of legalese such as come with the RSAREF toolkit. The Diffie-Hellman key exchange key size limit is also larger than the old RSA limit, so PGP encryption is actually more secure, now. The new SHA1 hash function is better than MD5, so signatures are more secure, now, too. The conventional encryption used is all sound, and definitely not the weak link in the chain. This much is good news.
The bad news, of course, is that there will be some interoperability problems, since no earlier versions of PGP can handle these algorithm, and the new PGP freeware doesn't support the old RSA algorithm unless you purchase the RSA support separately.
Protect Your Privacy: A Guide for PGP Users by William Stallings Prentice Hall PTR ISBN 0-13-185596-4 US $19.95 PGP: Pretty Good Privacy by Simson Garfinkel O'Reilly & Associates, Inc. ISBN 1-56592-098-8 US $24.95 E-Mail_Security, How To Keep Your Electronic Messages Private (covers PGP & PEM) by Bruce Schneier 365 pages 1995 pub: John Wiley & Sons, Inc. ISBN 0-471-05318-X $24.95 US The Computer Privacy Handbook: A Practical Guide to E-Mail Encryption, Data Protection, and PGP PRivacy Software by André Bacard Peachpit Press ISBN 1-56609-171-3 US $24.95 800-283-9444 or 510-548-4393 THE OFFICIAL PGP USER'S GUIDE by Philip R. Zimmermann MIT Press April 1995 - 216 pp. - paper - US $14.95 - ISBN 0-262-74017-6 ZIMPP Standard PGP documentation neatly typeset and bound. PGP SOURCE CODE AND INTERNALS by Philip R. Zimmermann April 1995 - 804 pp. - US $55.00 - 0-262-24039-4 ZIMPH How to Use PGP, 61 pages, (Pub #121) from the Superior Broadcasting Company, Box 1533-N, Oil City, PA 16301, phone: (814) 678-8801 (about US $10-$13).
Pretty Good Privacy is legal if you follow these rules:
Don't export PGP from the USA except to Canada, or from Canada except to the USA, without a license (except that printed books containing source code are OK to export).
If you are in the USA, use either the commercial PGP (licensed for commercial use) or MIT PGP using RSAREF (limited to personal, noncommercial use), or use one of the versions of PGP that doesn't support RSA encryption and digital signatures and use th e Diffie-Hellman and DSA algorithms (that aren't patented).
Outside of the USA, where RSA is not patented, you may prefer to use a version of PGP (2.6.3i) that doesn't use RSAREF to avoid the restrictions of that license.
If you are in a country where the IDEA cipher patent holds in software (including the USA and some countries in Europe), make sure you are licensed to use the IDEA cipher commercially before using PGP commercially. (No separate license is required to u se the freeware PGP for personal, noncommercial use). For direct IDEA licensing, contact Ascom Systec:
Erhard Widmer, Ascom Systec AG, Dep't. CMVV Phone +41 64 56 59 83 Peter Hartmann, Ascom Systec AG, Dep't. CMN Phone +41 64 56 59 45 Fax: +41 64 56 59 90 e-mail: IDEA@ascom.ch Mail address: Gewerbepark, CH-5506 Maegenwil (Switzerland)
Network Associates, Inc., has an exclusive marketing agreement for commercial distribution of Philip Zimmermann's copyrighted code. (Selling shareware/freeware disks or connect time is OK, as is building on older GPL versions of PGP.)
If you modify PGP (other than porting it to another platform, fixing a bug, or adapting it to another compiler), don't call it PGP (TM) or Pretty Good Privacy (TM) without Philip Zimmermann's permission.
Philip Zimmermann was under investigation for alleged violation of export regulations, with a grand jury hearing evidence for about 28 months, ending 11 January 1996. The Federal Government chose not to comment on why it decided to not prosecute, nor i s it likely to. The Commerce Secretary stated that he would seek relaxed export controls for cryptographic products, since studies show that U. S. industry is being harmed by current regulations. Philip endured some serious threats to his livelihood and f reedom, as well as some very real legal expenses, for the sake of your right to electronic privacy.
The battle is won, but the war is not over. The regulations that caused him so much grief and which continue to dampen cryptographic development, harm U. S. industry, and do violence to the U. S. National Security by eroding the First Ammendment of the U. S. Constitution and encouraging migration of cryptographic industry outside of the U. S. A. are still on the books.
If you are a U. S. Citizen, please write to your U. S. Senators, Congressional Representative, President, and Vice President pleading for a more sane and fair cryptographic policy. Several legislative efforts will, if successful, relax the export controls of cryptographic software from the U.S.
Within the U.S. there is no legal obstacle for use of strong encryption.
In an ideal world everyone would have the right to use encryption. Unfortunately, your right to use encryption may be restricted or does not exist.
In France, the government prohibits the use of encryption without prior permission, that you won't get if you are a private citizen.
Germany is said to consider banning the use and distribution of strong cryptographic software in the name of "national security."
United Kingdom may adopt a key escrow system.
For a recent update on the legal situation see The Crypto Law Survey http://cwis.kub.nl/~frw/people/koops/lawsurvy.htm
PGP can do conventional encryption only of a file (-c) option, but you might want to investigate some of the other alternatives if you do this a lot.
Alternatives include Quicrypt and Atbash2 for DOS, DLOCK for DOS & UNIX, Curve Encrypt (for the Mac), HPACK (many platforms), and a few others.
Quicrypt is interesting in that it comes in two flavors: shareware exportable and registered secure. Atbash2 is interesting in that it generates ciphertext that can be read over the telephone or sent by Morse code. DLOCK is a no-frills strong encryptio n program with complete source code. Curve Encrypt has certain user-friendliness advantages. HPACK is an archiver (like ZIP or ARC), but with strong encryption. A couple of starting points for your search are:
If you have the Norton Utilities, Norton WipeInfo is pretty good. I use DELETE.EXE in del110.zip, which is really good at deleting existing files, but doesn't wipe "unused" space.
PGPfone is for private telephone calls over a modem or the Internet.
Bill Dorsey, Pat Mullarky, and Paul Rubin have come out with a program called Nautilus that enables you to engage in secure voice conversations between people with multimedia PCs and modems capable of at least 7200 bps (but 14.4 kbps is better). See:
Secure File System (SFS) is a DOS device driver that encrypts an entire partition on the fly using SHA in feedback mode.
Secure Drive also encrypts an entire DOS partition, using IDEA, which is patented.
Secure Device is a DOS device driver that encrypts a virtual, file-hosted volume with IDEA.
Cryptographic File System (CFS) is a Unix device driver that uses DES. CryptDisk is a ShareWare package for Macintosh that uses strong IDEA encryption like PGP.
PGPDisk is also available somewhere at http://www.nai.com.
S/MIME is gaining a foothold on the secure email market, but my experience with it has been rather negative. Current implementations of S/MIME (1) don't allow secure key lengths to be used except in "U. S. Only" versions, (2) require payment of an annual fee to a key certification authority who verifies only that you got email to your key certificate's address at least once, (3) have much more limited key management facilities than PGP, and (4) the first time I tried to make S/MIME work, it flat out failed to perform as advertised. On the positive side, S/MIME is integrated into email packages like Microsoft Outlook 98 and Netscape Messenger almost as well as PGP is integrated into Eudora, and once the kinks are taken out, the secure version of S/MIME (1024-bit RSA keys and 128-bit RC-2 keys) will be good enough for most people. The "export" edition (512-bit RSA keys and 40-bit RC-2 keys) is a very bad idea, because it gives a false sense of security.
RIPEM is the third most popular freeware email encryption package, but it is losing ground fast. I like PGP better for lots of reasons, but if for some reason you want to check or generate a PEM signature (and if you are very tolerant of arcane and confusing command line interfaces), get a copy from ftp://idea.sec.dsi.unimi.it/pub/crypt/code/.
The latest PGP version will interact with key servers automatically if you are connected to the Internet and if you configure them to. For manual key publication, send mail to one of these addresses with the single word "help" in the subject line to fi nd out how to use them. These servers synchronize keys with each other. There are other key servers, too.
Yes and no. Yes, it is secure against most human attackers when used on a physically secure system in accordance with its instructions. This includes using a good passphrase to protect your private keys and keeping your passphrase and private keys truly private. No, it is not secure if you don't understand what you are doing. It is also true that God knows your thoughts even before you encrypt them, so you can't hide anything from Him. http://ebible.org/bible/web/Psalms.htm#C139V1
Yes. Please only do so in appropriate forums, and provide pointers to the home location of this FAQ.
Michael Paul Johnson email@example.com maintains this FAQ. My PGP public keys are at ftp://ebible.org/pub/mpjdhkey.asc (Diffie-Hellman/DSA) and ftp://ebible.org/pub/mpjkey.asc (RSA) as well as on the public key servers.
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