1998-10-06 12:10:02 +00:00
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2000-09-14 12:20:30 +00:00
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GNUPG FREQUENTLY ASKED QUESTIONS
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2000-10-24 15:35:13 +00:00
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2001-09-13 16:26:00 +00:00
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Version: 1.5.5
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Last-Modified: Sep 13, 2001
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2000-10-19 18:33:09 +00:00
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Maintained-by: Nils Ellmenreich <nils 'at' gnupg.org>
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2000-09-14 12:20:30 +00:00
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2000-10-24 15:35:13 +00:00
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2000-09-14 12:20:30 +00:00
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This is the GnuPG FAQ. The latest HTML version is available
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2000-10-02 13:12:00 +00:00
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here. <http://www.gnupg.org/faq.html>
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2000-09-14 12:20:30 +00:00
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The index is generated automatically, so there may be errors here. Not
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all questions may be in the section they belong to. Suggestions about
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how to improve the structure of this FAQ are welcome.
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2000-11-30 11:48:42 +00:00
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Please send additions and corrections to the maintainer. It would be
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most convenient if you could provide the answer to be included
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here. Your help is very much appreciated.
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Please, don't send message like "This should be a FAQ - what's the
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2001-02-20 14:18:55 +00:00
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answer?". If it hasn't been asked before, it isn't a FAQ. In that case
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2000-11-30 11:48:42 +00:00
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you could search in the mailing list archive.
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2000-09-14 12:20:30 +00:00
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2000-10-02 13:12:00 +00:00
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2000-09-14 12:20:30 +00:00
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1. GENERAL
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1.1) What is GnuPG?
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1.2) Is GnuPG compatible with PGP?
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2001-02-20 14:18:55 +00:00
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2. SOURCES of INFORMATION
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2000-09-14 12:20:30 +00:00
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2.1) Where can I find more information?
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2.2) Where do I get GnuPG?
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1998-10-06 12:10:02 +00:00
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2000-09-14 12:20:30 +00:00
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3. INSTALLATION
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3.1) Which OSes does GnuPG run on?
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3.2) Which random gatherer should I use?
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3.3) How do I include support for RSA and IDEA?
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1998-10-06 12:10:02 +00:00
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2000-09-14 12:20:30 +00:00
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4. USAGE
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4.1) What is the recommended key size?
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4.2) Why does it sometimes take so long to create keys?
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4.3) And it really takes long when I work on a remote system. Why?
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4.4) What is the difference between options and commands?
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4.5) I can't delete an user id because it is already deleted on my public
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2000-10-02 13:12:00 +00:00
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keyring?
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2001-08-30 16:39:23 +00:00
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4.6) I can't delete the secret key because my public key disappeared?
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4.7) What are trust, validity and ownertrust?
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4.8) How do I sign a patch file?
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4.9) Where is the "encrypt-to-self" option?
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4.10) How can I get rid of the Version and Comment headers in armored
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2000-09-14 12:20:30 +00:00
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messages?
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2001-08-30 16:39:23 +00:00
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4.11) What does the "You are using the xxxx character set." mean?
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4.12) How can a get list of key IDs used to encrypt a message?
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4.13) I can't decrypt my symmetrical only (-c) encrypted message with
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2000-09-14 12:20:30 +00:00
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a new version of GnuPG.
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2001-09-13 16:26:00 +00:00
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4.14) How can I use GnuPG in an automated environment?
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2001-08-30 16:39:23 +00:00
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4.15) Which email-client can I use with GnuPG?
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4.16) Can't we have a gpg library?
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4.17) I have successfully generated a revocation certificate, but I don't
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2001-05-21 16:19:34 +00:00
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understand how to send it to the key servers.
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2001-08-30 16:39:23 +00:00
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4.18) How do I put my keyring in a different directory?
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1998-10-06 12:10:02 +00:00
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2000-09-14 12:20:30 +00:00
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5. COMPATIBILITY ISSUES
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2001-02-20 14:18:55 +00:00
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5.1) How can I encrypt a message with GnuPG so that PGP is able to decrypt it?
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2000-10-02 13:12:00 +00:00
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5.2) How do I migrate from PGP 2.x to GnuPG?
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2001-02-20 14:18:55 +00:00
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5.3) (removed)
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2000-10-02 13:12:00 +00:00
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5.4) Why is PGP 5.x not able to encrypt messages with some keys?
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5.5) Why is PGP 5.x not able to verify my messages?
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5.6) How do I transfer owner trust values from PGP to GnuPG?
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2001-02-20 14:18:55 +00:00
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5.7) PGP does not like my secret key.
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1998-10-06 12:10:02 +00:00
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2000-09-14 12:20:30 +00:00
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6. PROBLEMS and ERROR MESSAGES
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6.1) Why do I get "gpg: Warning: using insecure memory!"
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2000-11-16 20:29:54 +00:00
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6.2) Large File Support doesn't work ..
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6.3) In the edit menu the trust values is not displayed correctly after
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2000-09-14 12:20:30 +00:00
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signing uids - why?
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2000-11-16 20:29:54 +00:00
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6.4) What does "skipping pubkey 1: already loaded" mean?
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6.5) GnuPG 1.0.4 doesn't create ~/.gnupg ...
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6.6) An ElGamal signature does not verify anymore since version 1.0.2 ...
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6.7) Old versions of GnuPG can't verify ElGamal signatures
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6.8) When I use --clearsign, the plain text has sometimes extra dashes
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2000-09-14 12:20:30 +00:00
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in it - why?
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2000-11-16 20:29:54 +00:00
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6.9) What is the thing with "can't handle multiple signatures"?
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6.10) If I submit a key to a keyserver, nothing happens ...
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2000-12-07 20:14:47 +00:00
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6.11) I get "gpg: waiting for lock ..."
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2000-12-14 10:19:15 +00:00
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6.12) Older gpg's (e.g., 1.0) have problems with keys from newer gpgs ...
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2000-12-19 15:39:57 +00:00
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6.13) With 1.0.4, I get "this cipher algorithm is deprecated ..."
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2001-04-19 11:40:45 +00:00
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6.14) Some dates are displayed as ????-??-??, why?
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6.15) I still have a problem. How do I report a bug?
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6.16) Why doesn't GnuPG support X509 certificates?
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2001-06-13 13:07:48 +00:00
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6.17) Why do national characters in my user ID look funny?
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2001-06-22 09:25:55 +00:00
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6.18) I get 'sed' errors when running ./configure on Mac OS X ...
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1998-10-06 12:10:02 +00:00
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2000-09-14 12:20:30 +00:00
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7. ADVANCED TOPICS
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7.1) How does this whole thing work?
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7.2) Why are some signatures with an ELG-E key valid?
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7.3) How does the whole trust thing work?
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7.4) What kind of output is this: "key C26EE891.298, uid 09FB: ...."?
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7.5) How do I interpret some of the informational outputs?
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7.6) Are the header lines of a cleartext signature part of the signed
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material?
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2001-03-16 11:03:43 +00:00
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7.7) What is the list of preferred algorithms?
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7.8) How do I change the list of preferred algorithms?
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1998-10-06 12:10:02 +00:00
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2000-09-14 12:20:30 +00:00
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8. ACKNOWLEDGEMENTS
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1998-10-06 12:10:02 +00:00
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2000-09-14 12:20:30 +00:00
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1. GENERAL
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1998-10-06 12:10:02 +00:00
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2000-09-14 12:20:30 +00:00
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1.1) What is GnuPG?
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1998-10-06 12:10:02 +00:00
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2000-09-14 12:20:30 +00:00
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GnuPG stands for GNU Privacy Guard and <http://www.gnupg.org>
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is GNU's tool for secure communication and data storage.
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It can be used to encrypt data and to create digital signatures.
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It includes an advanced key management facility and is compliant
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with the proposed OpenPGP Internet standard as described in
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RFC 2440. As <http://www.gnupg.org/rfc2440.html>
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such, it is aimed to be compatible with PGP from NAI Inc.
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1998-10-06 12:10:02 +00:00
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2000-09-14 12:20:30 +00:00
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1.2) Is GnuPG compatible with PGP?
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1998-10-06 12:10:02 +00:00
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2000-09-14 12:20:30 +00:00
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In general, yes. GnuPG and newer PGP releases should be implementing
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the OpenPGP standard. But there are some interoperability
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problems. See questions 5.1ff. for details.
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1998-10-06 12:10:02 +00:00
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2001-02-20 14:18:55 +00:00
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2. SOURCES of INFORMATION
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1998-10-06 12:10:02 +00:00
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2000-09-14 12:20:30 +00:00
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2.1) Where can I find more information?
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1998-10-06 12:10:02 +00:00
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2000-09-14 12:20:30 +00:00
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Here's a list of on-line resources:
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1998-10-06 12:10:02 +00:00
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2000-09-14 12:20:30 +00:00
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<http://www.gnupg.org/docs.html> is the
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documentation page. Have a look at the HOWTOs and the GNU Privacy
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Handbook (GPH, available in English, Spanish and Russian). The
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latter provides a detailed user's guide to GnuPG. You'll also find a
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document about how to convert from PGP 2.x to GnuPG.
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1998-10-06 12:10:02 +00:00
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2000-09-14 12:20:30 +00:00
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On <http://lists.gnupg.org>
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2001-07-10 13:05:54 +00:00
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you'll find an online archive of the GnuPG mailing lists. Most
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interesting should be gnupg-users for all user-related issues and
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gnupg-devel if you want to get in touch with the developers.
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In addition, searchable archives can be found on MARC, e.g.:
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GnuPG-users: <http://marc.theaimsgroup.com/?l=gnupg-users&r=1&w=2>,
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GnuPG-devel: <http://marc.theaimsgroup.com/?l=gnupg-devel&r=1&w=2>.
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1998-10-06 12:10:02 +00:00
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2000-09-14 12:20:30 +00:00
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*PLEASE:*
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Before posting to a list, read this FAQ and the available
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2000-10-24 15:35:13 +00:00
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documentation. In addition, search the list archive - maybe your
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question has already been discussed. This way you help people focus
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on topics that have not yet been resolved.
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2000-09-14 12:20:30 +00:00
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2001-01-25 18:31:06 +00:00
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The GnuPG source distribution contains a subdirectory
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./doc where some additional documentation is located
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(mainly interesting for hackers, not the casual user).
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2000-09-14 12:20:30 +00:00
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2.2) Where do I get GnuPG?
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2000-11-28 15:53:59 +00:00
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You can download the GNU Privacy Guard from its primary FTP server
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2000-09-14 12:20:30 +00:00
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ftp.gnupg.org or from
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one of the mirrors: <http://www.gnupg.org/mirror.html>
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2000-10-19 18:33:09 +00:00
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The current version is 1.0.4, please upgrade to this version as it
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fixes a security bug regarding the verification of multiple signatures.
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2000-09-14 12:20:30 +00:00
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3. INSTALLATION
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3.1) Which OSes does GnuPG run on?
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It should run on most Unices as well as Windows 95 and Windows NT. A
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list of OSes reported to be OK is presented at
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http://www.gnupg.org/gnupg.html#supsys .
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3.2) Which random gatherer should I use?
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"Good" random numbers are crucial for the security of your
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encryption. Different operating systems provide a variety of more or
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less quality random data. Linux and *BSD provide kernel generated
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random data through /dev/random - this should be the preferred
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choice on these systems. Also Solaris users with the SUNWski package
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installed have a /dev/random. In these cases, use the configure
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2000-10-24 15:35:13 +00:00
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option --enable-static-rnd=linux. In addition, there's
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also the kernel random device by Andi Maier
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< http://www.cosy.sbg.ac.at/~andi>
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<http://www.cosy.sbg.ac.at/~andi>, but it's still beta. Use at
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own risk!
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2000-09-14 12:20:30 +00:00
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On other systems, the Entropy Gathering Daemon (EGD) is a good
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2000-10-24 15:35:13 +00:00
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choice. It is a perl-daemon that monitors system activity and hashes
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2000-09-14 12:20:30 +00:00
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it into random data. See the download page <http://www.gnupg.org/download.html>
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how to obtain egd. Use --enable-static-rnd=egd here.
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If the above options do not work, you can use the random number
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generator "unix". This is *very* slow and should be
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avoided. The random quality isn't very good so don't use it on
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sensitive data.
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3.3) How do I include support for RSA and IDEA?
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2000-10-02 13:12:00 +00:00
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RSA is included as of GnuPG 1.0.3.
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2000-09-14 12:20:30 +00:00
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2000-10-02 13:12:00 +00:00
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The official GnuPG distribution does not contain IDEA due to a
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patent restriction. The patent does not expire before 2007 so don't
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expect official support before then.
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2001-09-13 16:26:00 +00:00
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However, there is an unofficial module to include it even
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2000-10-02 13:12:00 +00:00
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in earlier version of GnuPG. It's available from
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2000-09-14 12:20:30 +00:00
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<ftp://ftp.gnupg.org/pub/gcrypt/contrib/>
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2000-10-02 13:12:00 +00:00
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<ftp://ftp.gnupg.org/pub/gcrypt/contrib/>. Look for idea.c.
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Compilation directives are in the headers of these files. Then add
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the following line to your ~/.gnupg/options:
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2000-09-14 12:20:30 +00:00
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load-extension idea
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2001-06-15 13:27:15 +00:00
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2000-09-14 12:20:30 +00:00
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4. USAGE
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4.1) What is the recommended key size?
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1024 bit for DSA signatures; even for plain ElGamal
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1998-10-06 12:10:02 +00:00
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signatures this is sufficient as the size of the hash
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2000-09-14 12:20:30 +00:00
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is probably the weakest link if the key size is larger
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1998-10-06 12:10:02 +00:00
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than 1024 bits. Encryption keys may have greater sizes,
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2000-11-16 20:29:54 +00:00
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but you should then check the fingerprint of this key:
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2001-06-15 13:27:15 +00:00
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"gpg --fingerprint <user ID>".
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1998-10-06 12:10:02 +00:00
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2000-11-16 20:29:54 +00:00
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As for the key algorithms, you should stick with the default (i.e.,
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DSA signature and ElGamal encryption). A ElGamal signing key has the
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following disadvantages: the signature is larger, it is hard to
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create such a key useful for signatures which can withstand some
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real world attacks, you don't get any extra security compared to
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2000-12-07 20:14:47 +00:00
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DSA, there might be compatibility problems with certain PGP
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2000-11-16 20:29:54 +00:00
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versions. It has only been introduced because at the time it was
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2001-09-13 16:26:00 +00:00
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not clear whether there was a patent on DSA.
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2000-11-16 20:29:54 +00:00
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2000-09-14 12:20:30 +00:00
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4.2) Why does it sometimes take so long to create keys?
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The problem here is that we need a lot of random bytes and for that
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we (on Linux the /dev/random device) must collect some random data.
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It is really not easy to fill the Linux internal entropy buffer; I
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talked to Ted Ts'o and he commented that the best way to fill the
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buffer is to play with your keyboard. Good security has its price.
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What I do is to hit several times on the shift, control, alternate,
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2000-12-07 20:14:47 +00:00
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and caps lock keys, because these keys do not produce output to the
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2000-09-14 12:20:30 +00:00
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screen. This way you get your keys really fast (it's the same thing
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2000-10-02 13:12:00 +00:00
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PGP2 does).
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2000-09-14 12:20:30 +00:00
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Another problem might be another program which eats up your random
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bytes (a program (look at your daemons) that reads from
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/dev/[u]random).
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4.3) And it really takes long when I work on a remote system. Why?
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Don't do this at all! You should never create keys or even use GnuPG
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on a remote system because you normally have no physical control
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over your secret key ring (which is in most cases vulnerable to
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advanced dictionary attacks) - I strongly encourage everyone to only
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create keys on a local computer (a disconnected laptop is probably
|
|
|
|
the best choice) and if you need it on your connected box (I know:
|
|
|
|
We all do this) be sure to have a strong password for your account
|
|
|
|
and for your secret key and that you can trust your system
|
|
|
|
administrator.
|
|
|
|
|
|
|
|
When I check GnuPG on a remote system via ssh (I have no Alpha here
|
|
|
|
;-) I have the same problem. It takes a *very* long time to create
|
|
|
|
the keys, so I use a special option, --quick-random, to generate
|
|
|
|
insecure keys which are only good for some tests.
|
|
|
|
|
|
|
|
4.4) What is the difference between options and commands?
|
|
|
|
|
|
|
|
If you do a 'gpg --help', you will get two separate lists. The first
|
|
|
|
is a list of commands. The second is a list of options. Whenever you
|
|
|
|
run GPG, you *must* pick exactly one command (with one
|
|
|
|
exception, see below). You *may* pick one or more options.
|
|
|
|
The command should, just by convention, come at the end of the
|
|
|
|
argument list, after all the options. If the command takes a file
|
|
|
|
(all the basic ones do), the filename comes at the very end. So the
|
|
|
|
basic way to run gpg is:
|
|
|
|
|
|
|
|
gpg [--option something] [--option2] [--option3 something] --command file
|
|
|
|
|
|
|
|
Some options take arguments, for example the --output option (which
|
|
|
|
can be abbreviated -o) is an option that takes a filename. The
|
|
|
|
option's argument must follow immediately after the option itself,
|
|
|
|
otherwise gpg doesn't know which option the argument is supposed to
|
|
|
|
go with. As an option, --output and its filename must come before
|
|
|
|
the command. The --recipient (-r) option takes a name or keyid to
|
|
|
|
encrypt the message to, which must come right after the -r argument.
|
|
|
|
The --encrypt (or -e) command comes after all the options followed
|
|
|
|
by the file you wish to encrypt. So use
|
|
|
|
|
|
|
|
gpg -r alice -o secret.txt -e test.txt
|
|
|
|
|
|
|
|
If you write the options out in full, it is easier to read
|
|
|
|
|
|
|
|
gpg --recipient alice --output secret.txt --encrypt test.txt
|
|
|
|
|
|
|
|
If you're saving it in a file called ".txt" then you'd probably
|
|
|
|
expect to see ASCII-armored text in there, so you need to add the
|
|
|
|
--armor (-a) option, which doesn't take any arguments.
|
|
|
|
|
|
|
|
gpg --armor --recipient alice --output secret.txt --encrypt test.txt
|
|
|
|
|
|
|
|
If you imagine square brackets around the optional parts, it becomes
|
|
|
|
a bit clearer:
|
|
|
|
|
|
|
|
gpg [--armor] [--recipient alice] [--output secret.txt] --encrypt test.txt
|
|
|
|
|
|
|
|
The optional parts can be rearranged any way you want.
|
|
|
|
|
|
|
|
gpg --output secret.txt --recipient alice --armor --encrypt test.txt
|
|
|
|
|
|
|
|
If your filename begins with a hyphen (e.g. "-a.txt"), gnupg assumes
|
|
|
|
this is an option and may complain. To avoid this you have either
|
|
|
|
to use "./-a.txt" or stop the option and command processing with two
|
|
|
|
hyphens: "-- -a.txt".
|
|
|
|
|
|
|
|
*The exception:* signing and encrypting at the same time. Use
|
|
|
|
gpg [--options] --sign --encrypt foo.txt
|
|
|
|
|
|
|
|
|
|
|
|
4.5) I can't delete an user id because it is already deleted on my public
|
2000-10-02 13:12:00 +00:00
|
|
|
keyring?
|
2000-09-14 12:20:30 +00:00
|
|
|
|
|
|
|
Because you can only select from the public key ring, there is no
|
|
|
|
direct way to do this. However it is not very complicated to do it
|
|
|
|
anyway. Create a new user id with exactly the same name and you
|
|
|
|
will see that there are now two identical user ids on the secret
|
|
|
|
ring. Now select this user id and delete it. Both user ids will be
|
|
|
|
removed from the secret ring.
|
|
|
|
|
2001-08-30 16:39:23 +00:00
|
|
|
4.6) I can't delete the secret key because my public key disappeared?
|
|
|
|
|
|
|
|
To select a key a search is always done on the public keyring,
|
|
|
|
therefore it is not possible to select an secret key without
|
|
|
|
having the public key. Normally it shoud never happen that the
|
|
|
|
public key got lost but the secret key is still available. The
|
|
|
|
reality is different, so we GnuPG implements a special way to do
|
|
|
|
deal with it: Simply use the long keyid which you can figure out
|
|
|
|
by using the --with-colons options (it is the fifth field in the
|
|
|
|
lines beginning with "sec").
|
|
|
|
|
|
|
|
4.7) What are trust, validity and ownertrust?
|
2000-09-14 12:20:30 +00:00
|
|
|
|
|
|
|
"ownertrust" is used instead of "trust" to make clear that this is
|
|
|
|
the value you have assigned to a key to express how much you trust
|
|
|
|
the owner of this key to correctly sign (and so introduce) other
|
|
|
|
keys. "validity", or calculated trust, is a value which says how
|
|
|
|
much GnuPG thinks a key is valid (that it really belongs to the one
|
|
|
|
who claims to be the owner of the key). For more see the chapter
|
|
|
|
"The Web of Trust" in the Manual.
|
|
|
|
|
2001-08-30 16:39:23 +00:00
|
|
|
4.8) How do I sign a patch file?
|
2000-09-14 12:20:30 +00:00
|
|
|
|
|
|
|
Use "gpg --clearsign --not-dash-escaped ...". The problem with
|
|
|
|
--clearsign is that all lines starting with a dash are quoted with
|
|
|
|
"- "; obviously diff produces many of lines starting with a dash and
|
|
|
|
these are then quoted and that is not good for patch ;-). To use a
|
|
|
|
patch file without removing the cleartext signature, the special
|
|
|
|
option --not-dash-escaped may be used to suppress generation of
|
|
|
|
these escape sequences. You should not mail such a patch because
|
|
|
|
spaces and line endings are also subject to the signature and a
|
|
|
|
mailer may not preserve these. If you want to mail a file you can
|
|
|
|
simply sign it using your MUA.
|
|
|
|
|
2001-08-30 16:39:23 +00:00
|
|
|
4.9) Where is the "encrypt-to-self" option?
|
2000-09-14 12:20:30 +00:00
|
|
|
|
|
|
|
Use "--encrypt-to your_keyid". You can use more than one of these
|
|
|
|
options. To temporary override the use of this additional keys, you
|
|
|
|
can use the option "--no-encrypt-to".
|
|
|
|
|
2001-08-30 16:39:23 +00:00
|
|
|
4.10) How can I get rid of the Version and Comment headers in armored
|
2000-09-14 12:20:30 +00:00
|
|
|
messages?
|
|
|
|
|
|
|
|
Use "--no-version --comment ''". Note that the left over blank line
|
|
|
|
is required by the protocol.
|
|
|
|
|
2001-08-30 16:39:23 +00:00
|
|
|
4.11) What does the "You are using the xxxx character set." mean?
|
2000-09-14 12:20:30 +00:00
|
|
|
|
|
|
|
This note is printed when UTF8 mapping has to be done. Make sure
|
|
|
|
that the displayed charset is the one you have activated on your
|
|
|
|
system "iso-8859-1" is the most used one, so this is the default.
|
|
|
|
You can change the charset with the option "--charset". It is
|
|
|
|
important that you active character set matches the one displayed -
|
|
|
|
if not, restrict yourself to plain 7 bit ASCII and no mapping has to
|
|
|
|
be done.
|
|
|
|
|
2001-08-30 16:39:23 +00:00
|
|
|
4.12) How can a get list of key IDs used to encrypt a message?
|
2000-09-14 12:20:30 +00:00
|
|
|
|
2000-11-28 15:53:59 +00:00
|
|
|
gpg --batch --decrypt --list-only --status-fd 1 2>/dev/null | \
|
|
|
|
awk '/^\[GNUPG:\] ENC_TO / { print $3 }'
|
2000-09-14 12:20:30 +00:00
|
|
|
|
2001-08-30 16:39:23 +00:00
|
|
|
4.13) I can't decrypt my symmetrical only (-c) encrypted message with
|
2000-09-14 12:20:30 +00:00
|
|
|
a new version of GnuPG.
|
|
|
|
|
|
|
|
There used to be a bug in GnuPG < 1.0.1 which happens only if 3DES
|
|
|
|
or Twofish has been used for symmetric only encryption (this has
|
|
|
|
never been the default). The bug has been fixed but to enable you
|
|
|
|
to decrypt old messages, you should run gpg with the option
|
|
|
|
"--emulate-3des-s2k-bug", decrypt the message and encrypt it again
|
|
|
|
without this option. The option will be removed in 1.1, so better
|
|
|
|
re-encrypt your message now.
|
|
|
|
|
2001-09-13 16:26:00 +00:00
|
|
|
4.14) How can I use GnuPG in an automated environment?
|
2000-09-14 12:20:30 +00:00
|
|
|
|
|
|
|
You should use the option --batch and don't use pass phrases as
|
|
|
|
there is usually no way to store it more secure than the secret
|
|
|
|
keyring itself. The suggested way to create the keys for the
|
|
|
|
automated environment is:
|
|
|
|
|
|
|
|
On a secure machine:
|
|
|
|
If you want to do automatic signing, create a signing
|
|
|
|
subkey for your key (edit menu, choose "addkey" and the DSA). [H
|
|
|
|
LI] Make sure that you use a passphrase (Needed by the current
|
|
|
|
implementation) gpg --export-secret-subkeys --no-comment foo
|
|
|
|
>secring.auto Copy secring.auto and the public keyring to a
|
|
|
|
test directory. Cd to this directory. gpg --homedir
|
|
|
|
. --edit foo and use "passwd" to remove the pass-phrase from the
|
|
|
|
subkeys. You may also want to remove all unused subkeys.
|
|
|
|
copy secring.auto to a floppy and carry it to the target box
|
|
|
|
On the target machine: Install secring.auto as secret
|
|
|
|
keyring. Now you can start your new service. It is a good
|
|
|
|
idea to install some intrusion detection system so that you
|
|
|
|
hopefully get a notice of an successful intrusion, so that you in
|
|
|
|
turn can revoke all the subkeys installed on that machine and
|
|
|
|
install new subkeys.
|
|
|
|
|
2001-08-30 16:39:23 +00:00
|
|
|
4.15) Which email-client can I use with GnuPG?
|
2000-10-24 15:35:13 +00:00
|
|
|
|
|
|
|
Using GnuPG to encrypt email is one of the most popular
|
|
|
|
uses. Several mail clients or mail user-agents (MUA) support GnuPG
|
|
|
|
at varying degrees. Simplifying a bit, there are two ways a mail can
|
|
|
|
be encrypted with GnuPG: the "old style" ASCII armor, i.e. plain
|
|
|
|
text encryption, and RFC2015 style (previously PGP/MIME, now
|
|
|
|
OpenPGP). The latter has full MIME support. Some MUAs support only
|
|
|
|
one of them, so whichever you actually use depends on your needs as
|
2000-12-07 20:14:47 +00:00
|
|
|
well as the capabilities of your addressee.
|
2000-10-24 15:35:13 +00:00
|
|
|
|
|
|
|
The following list is probably not exhaustive:
|
|
|
|
|
|
|
|
OpenPGP: Mutt (Unix), Emacs/Mew, Becky2 (Windows, with plugin),
|
2000-11-16 20:29:54 +00:00
|
|
|
TkRat (Unix). There is effort for a Mozilla plugin and
|
|
|
|
Emacs/GNUS has support in the current CVS.
|
2000-10-24 15:35:13 +00:00
|
|
|
|
|
|
|
ASCII: Emacs/{VM,GNUS}/MailCrypt, Mutt(Unix), Pine(Unix), and
|
|
|
|
probably many more.
|
|
|
|
|
2000-11-16 20:29:54 +00:00
|
|
|
A good overview of PGP-support is present at
|
|
|
|
http://cryptorights.org/pgp-users/pgp-mail-clients.html.
|
|
|
|
Direct GnuPG support is not mentioned, however, it certain cases it
|
|
|
|
may be possible to use a wrapper.
|
2000-09-14 12:20:30 +00:00
|
|
|
|
|
|
|
|
2001-08-30 16:39:23 +00:00
|
|
|
4.16) Can't we have a gpg library?
|
2000-12-07 20:14:47 +00:00
|
|
|
|
|
|
|
This has been frequently requested. However, the current viewpoint
|
|
|
|
of the GnuPG maintainers is that this would lead to several security
|
|
|
|
issues and will therefore not be implemented in the foreseeable
|
2000-12-14 10:19:15 +00:00
|
|
|
future. However, for some areas of areas of application gpgme could
|
|
|
|
do the trick. You'll find it at
|
|
|
|
ftp://ftp.guug.de/pub/gcrypt/alpha/gpgme
|
2000-12-07 20:14:47 +00:00
|
|
|
|
2001-05-21 16:19:34 +00:00
|
|
|
|
2001-08-30 16:39:23 +00:00
|
|
|
4.17) I have successfully generated a revocation certificate, but I don't
|
2001-05-21 16:19:34 +00:00
|
|
|
understand how to send it to the key servers.
|
|
|
|
|
|
|
|
Most keyservers don't accept a 'bare' revocation certificate. You
|
|
|
|
have to import the certificate into gpg first:
|
|
|
|
gpg --import my-revocation.asc
|
|
|
|
then send the revoked key to the keyservers:
|
|
|
|
gpg --keyserver certserver.pgp.com --send-keys mykeyid
|
|
|
|
(or use a keyserver web interface for this).
|
|
|
|
|
2001-07-12 12:44:48 +00:00
|
|
|
|
2001-08-30 16:39:23 +00:00
|
|
|
4.18) How do I put my keyring in a different directory?
|
2001-07-12 12:44:48 +00:00
|
|
|
|
|
|
|
GnuPG keeps several files in a special homedir directory. These
|
|
|
|
include the options file, pubring.gpg, secring.gpg, the trustdb, and
|
|
|
|
others. Gnupg will always create and use these files. On unices,
|
|
|
|
the homedir is usually ~/.gnupg; on Windows "C:\gnupg\".
|
|
|
|
|
|
|
|
If you want to put your keyrings somewhere else, use
|
|
|
|
--homedir /my/path/ to make gnupg create all its
|
|
|
|
files in that directory. Your keyring will be
|
|
|
|
"/my/path/pubring.gpg". This way you can store your secrets on a
|
|
|
|
floppy disk. Don't use "--keyring" as its purpose is to specify
|
|
|
|
additional keyring files.
|
|
|
|
|
|
|
|
|
2000-09-14 12:20:30 +00:00
|
|
|
5. COMPATIBILITY ISSUES
|
|
|
|
|
|
|
|
|
2001-02-20 14:18:55 +00:00
|
|
|
5.1) How can I encrypt a message with GnuPG so that PGP is able to decrypt it?
|
|
|
|
|
|
|
|
It depends on the PGP version.
|
|
|
|
|
|
|
|
PGP 2.x
|
2000-09-14 12:20:30 +00:00
|
|
|
|
2000-10-02 13:12:00 +00:00
|
|
|
You can't do that because PGP 2.x normally uses IDEA which is not
|
2001-02-20 14:18:55 +00:00
|
|
|
supported by GnuPG as it is patented (see 3.3), but if you
|
2000-10-02 13:12:00 +00:00
|
|
|
have a modified version of PGP you can try this:
|
2000-09-14 12:20:30 +00:00
|
|
|
|
|
|
|
gpg --rfc1991 --cipher-algo 3des ...
|
|
|
|
|
2001-02-20 14:18:55 +00:00
|
|
|
Please don't pipe the data to encrypt to gpg but provide it using a
|
2000-10-02 13:12:00 +00:00
|
|
|
filename; otherwise, PGP 2 will not be able to handle it.
|
|
|
|
|
2001-02-20 14:18:55 +00:00
|
|
|
As for conventional encryption, you can't do this for PGP 2.
|
|
|
|
|
|
|
|
|
|
|
|
PGP 5.x and higher
|
|
|
|
|
|
|
|
You need to provide two additional options:
|
|
|
|
--compress-algo 1 --cipher-algo cast5
|
|
|
|
|
|
|
|
You may also use "3des" instead of "cast5", "blowfish" does not
|
|
|
|
work with all versions of pgp5. You may also want to put
|
|
|
|
compress-algo 1 into your ~/.gnupg/options file - this does
|
|
|
|
not affect normal gnupg operation.
|
|
|
|
|
|
|
|
This applies to conventional encryption as well.
|
|
|
|
|
2000-10-02 13:12:00 +00:00
|
|
|
5.2) How do I migrate from PGP 2.x to GnuPG?
|
|
|
|
|
|
|
|
PGP 2 uses the RSA and IDEA encryption algorithms. Whereas the RSA
|
|
|
|
patent has expired and RSA is included as of GnuPG 1.0.3, the IDEA
|
|
|
|
algorithm is still patented until 2007. Under certain conditions you
|
|
|
|
may use IDEA even today. In that case, you may refer to Question
|
|
|
|
3.3 about how to add IDEA support to GnuPG and read
|
|
|
|
http://www.gnupg.org/gph/en/pgp2x.html
|
2000-12-07 20:14:47 +00:00
|
|
|
to perform the migration.
|
2000-10-02 13:12:00 +00:00
|
|
|
|
2000-09-14 12:20:30 +00:00
|
|
|
|
2001-02-20 14:18:55 +00:00
|
|
|
5.3) (removed)
|
2000-09-14 12:20:30 +00:00
|
|
|
|
2001-02-20 14:18:55 +00:00
|
|
|
(empty)
|
2000-09-14 12:20:30 +00:00
|
|
|
|
2000-10-02 13:12:00 +00:00
|
|
|
5.4) Why is PGP 5.x not able to encrypt messages with some keys?
|
2000-09-14 12:20:30 +00:00
|
|
|
|
|
|
|
PGP Inc refuses to accept ElGamal keys of type 20 even for
|
|
|
|
encryption. They only support type 16 (which is identical at least
|
|
|
|
for decryption). To be more inter-operable, GnuPG (starting with
|
|
|
|
version 0.3.3) now also uses type 16 for the ElGamal subkey which is
|
|
|
|
created if the default key algorithm is chosen. You may add an type
|
|
|
|
16 ElGamal key to your public key which is easy as your key
|
|
|
|
signatures are still valid.
|
|
|
|
|
2000-10-02 13:12:00 +00:00
|
|
|
5.5) Why is PGP 5.x not able to verify my messages?
|
2000-09-14 12:20:30 +00:00
|
|
|
|
|
|
|
PGP 5.x does not accept V4 signatures for data material but OpenPGP
|
2001-05-21 16:19:34 +00:00
|
|
|
requests generation of V4 signatures for all kind of data, that's why
|
|
|
|
GnuPG defaults to them. Use the option "--force-v3-sigs" to generate
|
|
|
|
V3 signatures for data.
|
2000-09-14 12:20:30 +00:00
|
|
|
|
2000-10-02 13:12:00 +00:00
|
|
|
5.6) How do I transfer owner trust values from PGP to GnuPG?
|
2000-09-14 12:20:30 +00:00
|
|
|
|
|
|
|
There is a script in the tools directory to help you: After you have
|
|
|
|
imported the PGP keyring you can give this command:
|
|
|
|
|
|
|
|
$ lspgpot pgpkeyring | gpg --import-ownertrust
|
|
|
|
|
|
|
|
where pgpkeyring is the original keyring and not the GnuPG one you
|
|
|
|
might have created in the first step.
|
|
|
|
|
2001-02-20 14:18:55 +00:00
|
|
|
5.7) PGP does not like my secret key.
|
2000-09-14 12:20:30 +00:00
|
|
|
|
2001-02-20 14:18:55 +00:00
|
|
|
Older PGPs probably bail out on some private comment packets used by
|
2000-09-14 12:20:30 +00:00
|
|
|
GnuPG. These packets are fully in compliance with OpenPGP; however
|
|
|
|
PGP is not really OpenPGP aware. A workaround is to export the
|
|
|
|
secret keys with this command:
|
2000-12-14 10:19:15 +00:00
|
|
|
$ gpg --export-secret-keys --no-comment -a your-key-id
|
|
|
|
|
|
|
|
Another possibility is this: by default, GnuPG encrypts your secret
|
|
|
|
key using the Blowfish symmetric algorithm. Older PGPs will only
|
|
|
|
understand 3DES, CAST5, or IDEA symmetric algorithms. Using the
|
|
|
|
following method you can re-encrypt your secret gpg key with a
|
|
|
|
different algo:
|
|
|
|
|
|
|
|
$ gpg --s2k-cipher-algo=CAST5 --s2k-digest-algo=SHA1 \
|
2001-02-20 14:18:55 +00:00
|
|
|
--compress-algo=1 --edit-key <username>
|
2000-12-14 10:19:15 +00:00
|
|
|
|
|
|
|
Then use passwd to change the password (just change it to the same
|
|
|
|
thing, but it will encrypt the key with CAST5 this time).
|
|
|
|
|
|
|
|
Now you can export it and PGP should be able to handle it.
|
2000-09-14 12:20:30 +00:00
|
|
|
|
2001-02-20 14:18:55 +00:00
|
|
|
For PGP 6.x the following options work to export a key:
|
|
|
|
$ gpg --s2k-cipher-algo 3des --compress-algo 1 --rfc1991 \
|
|
|
|
--export-secret-keys <Key-ID>
|
2000-09-14 12:20:30 +00:00
|
|
|
|
|
|
|
6. PROBLEMS and ERROR MESSAGES
|
|
|
|
|
|
|
|
6.1) Why do I get "gpg: Warning: using insecure memory!"
|
|
|
|
|
|
|
|
On many systems this program should be installed as
|
|
|
|
setuid(root). This is necessary to lock memory pages. Locking
|
2000-10-24 09:27:44 +00:00
|
|
|
memory pages prevents the operating system from writing them
|
2000-09-14 12:20:30 +00:00
|
|
|
to disk and thereby keeping your secret keys really secret. If you
|
|
|
|
get no warning message about insecure memory your operating system
|
|
|
|
supports locking without being root. The program drops root
|
|
|
|
privileges as soon as locked memory is allocated.
|
|
|
|
|
2000-10-24 15:35:13 +00:00
|
|
|
On UnixWare 2.x and 7.x you should install GnuPG with the
|
2000-12-07 20:14:47 +00:00
|
|
|
'plock' privilege to get the same effect:
|
2000-10-24 09:27:44 +00:00
|
|
|
filepriv -f plock /path/to/gpg
|
|
|
|
|
2000-09-14 12:20:30 +00:00
|
|
|
If you can't or don't want to install GnuPG setuid(root), you can
|
|
|
|
use the option "--no-secmem-warning" or put
|
2000-10-24 09:27:44 +00:00
|
|
|
no-secmem-warning in your ~/.gnupg/options file (this
|
|
|
|
disables the warning).
|
|
|
|
|
2001-01-25 18:31:06 +00:00
|
|
|
On some systems (e.g., Windows) GnuPG does not lock memory pages
|
|
|
|
and older GnuPG versions (<=1.0.4) issue the warning
|
2000-10-24 09:27:44 +00:00
|
|
|
gpg: Please note that you don't have secure memory
|
|
|
|
This warning can't be switched off by the above option because it
|
|
|
|
was thought to be a too serious issue. However, it confused users
|
|
|
|
too much so the warning was eventually removed.
|
|
|
|
|
2000-11-16 20:29:54 +00:00
|
|
|
6.2) Large File Support doesn't work ..
|
|
|
|
|
|
|
|
LFS is correctly working in post-1.0.4 CVS. If configure doesn't
|
|
|
|
detect it correctly, try a different (i.e., better) compiler. egcs
|
|
|
|
1.1.2 works fine, other gccs sometimes don't. BTW, several
|
|
|
|
compilation problems of GnuPG 1.0.3 and 1.0.4 on HP-UX and Solaris
|
|
|
|
were due to broken LFS support.
|
2000-09-14 12:20:30 +00:00
|
|
|
|
2000-11-16 20:29:54 +00:00
|
|
|
6.3) In the edit menu the trust values is not displayed correctly after
|
2000-09-14 12:20:30 +00:00
|
|
|
signing uids - why?
|
|
|
|
|
|
|
|
This happens because the some informations are stored immediately in
|
|
|
|
the trustdb, but the actual trust calculation can be done after the
|
|
|
|
save command. This is a not easy to fix design bug which will be
|
|
|
|
addressed in some future release.
|
|
|
|
|
2000-11-16 20:29:54 +00:00
|
|
|
6.4) What does "skipping pubkey 1: already loaded" mean?
|
|
|
|
|
|
|
|
As of GnuPG 1.0.3, the RSA algorithm is included. If you still have
|
|
|
|
a "load-extension rsa" in your .options files, the above message
|
|
|
|
occurs. Just remove the load command from the .options file.
|
|
|
|
|
|
|
|
6.5) GnuPG 1.0.4 doesn't create ~/.gnupg ...
|
|
|
|
|
|
|
|
That's a known bug, already fixed in the CVS (and will be in the
|
|
|
|
next release, of course).
|
|
|
|
|
|
|
|
6.6) An ElGamal signature does not verify anymore since version 1.0.2 ...
|
2000-09-14 12:20:30 +00:00
|
|
|
|
|
|
|
Use the option --emulate-md-encode-bug.
|
|
|
|
|
2000-11-16 20:29:54 +00:00
|
|
|
6.7) Old versions of GnuPG can't verify ElGamal signatures
|
2000-09-14 12:20:30 +00:00
|
|
|
|
|
|
|
Update to GnuPG 1.0.2 or newer.
|
|
|
|
|
|
|
|
|
2000-11-16 20:29:54 +00:00
|
|
|
6.8) When I use --clearsign, the plain text has sometimes extra dashes
|
2000-09-14 12:20:30 +00:00
|
|
|
in it - why?
|
|
|
|
|
|
|
|
This is called dash-escaped text and required by OpenPGP.
|
|
|
|
It always happens when a line starts with a dash ("-") and is needed
|
2000-10-02 13:12:00 +00:00
|
|
|
to make the lines that structure signature and text
|
|
|
|
(i.e., "-----BEGIN PGP SIGNATURE-----") to be the only lines that
|
|
|
|
start with two dashes.
|
2000-09-14 12:20:30 +00:00
|
|
|
|
2000-10-02 13:12:00 +00:00
|
|
|
If you use GnuPG to process those messages, the extra dashes are removed.
|
2000-09-14 12:20:30 +00:00
|
|
|
Good mail clients remove those extra dashes when displaying such a
|
|
|
|
message.
|
|
|
|
|
2000-11-16 20:29:54 +00:00
|
|
|
6.9) What is the thing with "can't handle multiple signatures"?
|
2000-10-17 12:41:51 +00:00
|
|
|
|
2000-10-17 13:30:26 +00:00
|
|
|
Due to different message formats GnuPG is not always able to split a
|
2000-11-28 15:53:59 +00:00
|
|
|
file with multiple signatures unambiguously into its parts. This
|
2000-10-17 13:30:26 +00:00
|
|
|
error message informs you that there is something wrong with the input.
|
2000-10-17 12:41:51 +00:00
|
|
|
|
|
|
|
The only way to have multiple signatures in a file is by using the
|
|
|
|
OpenPGP format with one-pass-signature packets (which is GnuPG's
|
|
|
|
default) or the cleartext signed format.
|
2000-09-14 12:20:30 +00:00
|
|
|
|
2000-11-16 20:29:54 +00:00
|
|
|
6.10) If I submit a key to a keyserver, nothing happens ...
|
2000-10-19 18:33:09 +00:00
|
|
|
|
|
|
|
You are most likely using GnuPG on Windows 1.0.2 or older. That's
|
|
|
|
feature isn't yet implemented, but it's a bug not to say it. Newer
|
|
|
|
versions issue a warning. Upgrade to 1.0.4 or newer.
|
|
|
|
|
2000-12-07 20:14:47 +00:00
|
|
|
6.11) I get "gpg: waiting for lock ..."
|
|
|
|
|
|
|
|
A previous gpg has most likely exited abnormally and left a lock
|
|
|
|
file. Go to ~/.gnupg and look for .*.lock files and remove them.
|
|
|
|
|
2000-12-14 10:19:15 +00:00
|
|
|
6.12) Older gpg's (e.g., 1.0) have problems with keys from newer gpgs ...
|
|
|
|
|
|
|
|
As of 1.0.3, keys generated with gpg are created with preferences to
|
|
|
|
TWOFISH (and AES since 1.0.4) and that also means that they have the
|
|
|
|
capability to use the new MDC encryption method. This will go into
|
|
|
|
OpenPGP soon and is also suppoted by PGP 7. This new method avoids
|
|
|
|
a (not so new) attack on all email encryption systems.
|
|
|
|
|
|
|
|
This in turn means that pre-1.0.3 gpg's have problems with newer
|
|
|
|
key. Because of security fixes, you should keep your gpg
|
|
|
|
installation in a recent state anyway. As a workaround, you can
|
|
|
|
force gpg to use a previous default cipher algo by putting
|
|
|
|
cipher-algo cast5 into your options file.
|
|
|
|
|
2000-12-19 15:39:57 +00:00
|
|
|
6.13) With 1.0.4, I get "this cipher algorithm is deprecated ..."
|
|
|
|
|
|
|
|
If you just generated a new key and get this message while
|
|
|
|
encrypting, you've witnessed a bug in 1.0.4. It uses the new AES
|
|
|
|
cipher Rijndael that is incorrectly being referred as
|
|
|
|
"deprecated". Ignore this warning, more recent versions of gpg are
|
|
|
|
corrected.
|
|
|
|
|
2001-04-19 11:40:45 +00:00
|
|
|
6.14) Some dates are displayed as ????-??-??, why?
|
|
|
|
|
|
|
|
Due to constraints in most libc implementations, dates beyond
|
|
|
|
2038-01-19 can't be displayed correctly. 64 bit OSes are not
|
|
|
|
affected by this problem. To avoid printing wrong dates, GnuPG
|
|
|
|
instead prints some question marks. To see the correct value, you
|
|
|
|
can use the options --with-colons and --fixed-list-mode.
|
|
|
|
|
|
|
|
6.15) I still have a problem. How do I report a bug?
|
2000-10-19 18:33:09 +00:00
|
|
|
|
|
|
|
Are you sure that it's not been mentioned somewhere on the mailing
|
|
|
|
lists? Did you have a look at the bug list (You'll find a link to
|
|
|
|
the list of reported bugs on the documentation page). If you're not
|
|
|
|
sure about it being a bug, you can send mail to the gnupg-devel
|
|
|
|
list. Otherwise, use the GUUG bug tracking system
|
|
|
|
http://bugs.guug.de/Reporting.html.
|
2000-09-14 12:20:30 +00:00
|
|
|
|
2001-04-19 11:40:45 +00:00
|
|
|
6.16) Why doesn't GnuPG support X509 certificates?
|
2001-04-06 09:59:50 +00:00
|
|
|
|
|
|
|
GnuPG, first and foremost, is an implementation of the OpenPGP
|
|
|
|
standard (RFC 2440), which is a competing infrastructure, different
|
|
|
|
from X509.
|
|
|
|
|
|
|
|
They are both public-key cryptosystems, but how the public keys are
|
|
|
|
actually handled is different.
|
|
|
|
|
2001-06-13 13:07:48 +00:00
|
|
|
|
|
|
|
6.17) Why do national characters in my user ID look funny?
|
|
|
|
|
|
|
|
According to OpenPGP, GnuPG encodes user id strings (and other
|
|
|
|
things) using UTF-8. In this encoding of Unicode, most national
|
|
|
|
characters get encoded as two- or three-byte sequences. For
|
|
|
|
example, å (0xE5 in ISO-8859-1) becomes Ã¥ (0xC3,
|
|
|
|
0xA5). This might also be the reason why keyservers can't find
|
|
|
|
your key.
|
|
|
|
|
2001-06-22 09:25:55 +00:00
|
|
|
6.18) I get 'sed' errors when running ./configure on Mac OS X ...
|
2001-06-13 13:07:48 +00:00
|
|
|
|
2001-06-22 09:25:55 +00:00
|
|
|
This will be fixed after GnuPG has been upgraded to
|
|
|
|
autoconf-2.50. Until then, find the line setting CDPATH in the
|
|
|
|
configure script and place a unset CDPATH statement
|
|
|
|
below it.
|
2001-06-13 13:07:48 +00:00
|
|
|
|
|
|
|
|
2000-09-14 12:20:30 +00:00
|
|
|
7. ADVANCED TOPICS
|
|
|
|
|
|
|
|
7.1) How does this whole thing work?
|
|
|
|
|
|
|
|
To generate a secret/public keypair, run gpg --gen-key
|
|
|
|
and choose the default values.
|
|
|
|
|
|
|
|
Data that is encrypted with a public key can only be decrypted by
|
|
|
|
the matching secret key. The secret key is protected by a password,
|
|
|
|
the public key is not.
|
|
|
|
|
|
|
|
So to send your friend a message, you would encrypt your message
|
|
|
|
with his public key, and he would only be able to decrypt it by
|
|
|
|
having the secret key and putting in the password to use his secret
|
|
|
|
key.
|
|
|
|
|
|
|
|
GnuPG is also useful for signing things. Things that are encrypted
|
|
|
|
with the secret key can be decrypted with the public key. To sign
|
|
|
|
something, a hash is taken of the data, and then the hash is in some
|
|
|
|
form encoded with the secret key. If someone has your public key, they
|
|
|
|
can verify that it is from you and that it hasn't changed by checking
|
|
|
|
the encoded form of the hash with the public key.
|
|
|
|
|
|
|
|
A keyring is just a large file that stores keys. You have a public
|
|
|
|
keyring where you store yours and your friend's public keys. You have
|
|
|
|
a secret keyring that you keep your secret key on, and be very careful
|
|
|
|
with this secret keyring: Never ever give anyone else access to it and
|
|
|
|
use a *good* passphrase to protect the data in it.
|
|
|
|
|
|
|
|
You can 'conventionally' encrypt something by using the option 'gpg
|
|
|
|
-c'. It is encrypted using a passphrase, and does not use public and
|
|
|
|
secret keys. If the person you send the data to knows that
|
|
|
|
passphrase, they can decrypt it. This is usually most useful for
|
|
|
|
encrypting things to yourself, although you can encrypt things to your
|
|
|
|
own public key in the same way. It should be used for communication
|
|
|
|
with partners you know and where it is easy to exchange the
|
|
|
|
passphrases (e.g. with your boy friend or your wife). The advantage
|
|
|
|
is that you can change the passphrase from time to time and decrease
|
|
|
|
the risk, that many old messages may be decrypted by people who
|
|
|
|
accidently got your passphrase.
|
|
|
|
|
|
|
|
You can add and copy keys to and from your keyring with the 'gpg
|
|
|
|
--import' and 'gpg --export' option. 'gpg --export-secret-keys' will
|
|
|
|
export secret keys. This is normally not useful, but you can generate
|
|
|
|
the key on one machine then move it to another machine.
|
|
|
|
|
|
|
|
Keys can be signed under the 'gpg --edit-key' option. When you sign a
|
|
|
|
key, you are saying that you are certain that the key belongs to the
|
|
|
|
person it says it comes from. You should be very sure that is really
|
|
|
|
that person: You should verify the key fingerprint
|
|
|
|
gpg --fingerprint user-id
|
|
|
|
over phone (if you really know the voice of the other person) or at a
|
|
|
|
key signing party (which are often held at computer conferences) or at
|
|
|
|
a meeting of your local GNU/Linux User Group.
|
|
|
|
|
|
|
|
Hmm, what else. You may use the option "-o filename" to force output
|
|
|
|
to this filename (use "-" to force output to stdout). "-r" just lets
|
|
|
|
you specify the recipient (which public key you encrypt with) on the
|
|
|
|
command line instead of typing it interactively.
|
|
|
|
|
|
|
|
Oh yeah, this is important. By default all data is encrypted in some
|
|
|
|
weird binary format. If you want to have things appear in ASCII text
|
|
|
|
that is readable, just add the '-a' option. But the preferred method
|
|
|
|
is to use a MIME aware mail reader (Mutt, Pine and many more).
|
|
|
|
|
|
|
|
There is a small security glitch in the OpenPGP (and therefore GnuPG)
|
|
|
|
system; to avoid this you should always sign and encrypt a message
|
|
|
|
instead of only encrypting it.
|
|
|
|
|
|
|
|
|
|
|
|
7.2) Why are some signatures with an ELG-E key valid?
|
|
|
|
|
|
|
|
These are ElGamal Key generated by GnuPG in v3 (rfc1991) packets.
|
|
|
|
The OpenPGP draft later changed the algorithm identifier for ElGamal
|
|
|
|
keys which are usable for signatures and encryption from 16 to 20.
|
|
|
|
GnuPG now uses 20 when it generates new ElGamal keys but still
|
|
|
|
accept 16 (which is according to OpenPGP "encryption only") if this
|
|
|
|
key is in a v3 packet. GnuPG is the only program which had used
|
1998-10-06 12:10:02 +00:00
|
|
|
these v3 ElGamal keys - so this assumption is quite safe.
|
|
|
|
|
|
|
|
|
2000-09-14 12:20:30 +00:00
|
|
|
7.3) How does the whole trust thing work?
|
|
|
|
|
|
|
|
It works more or less like PGP. The difference is that the trust is
|
|
|
|
computed at the time it is needed. This is one of the reasons for
|
|
|
|
the trustdb which holds a list of valid key signatures. If you are
|
|
|
|
not running in batch mode you will be asked to assign a trust
|
|
|
|
parameter (ownertrust) to a key.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
You can see the validity (calculated trust value) using this
|
|
|
|
command.
|
|
|
|
gpg --list-keys --with-colons
|
|
|
|
|
|
|
|
If the first field is "pub" or "uid", the second field shows you the
|
|
|
|
trust:
|
|
|
|
|
|
|
|
o = Unknown (this key is new to the system)
|
|
|
|
e = The key has expired
|
|
|
|
q = Undefined (no value assigned)
|
|
|
|
n = Don't trust this key at all
|
|
|
|
m = There is marginal trust in this key
|
|
|
|
f = The key is full trusted
|
|
|
|
u = The key is ultimately trusted; this is only used
|
|
|
|
for keys for which the secret key is also available.
|
|
|
|
r = The key has been revoked
|
|
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d = The key has been disabled
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The value in the "pub" record is the best one of all "uid" records.
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You can get a list of the assigned trust values (how much you trust
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the owner to correctly sign another person's key)
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gpg --list-ownertrust The first field is the
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fingerprint of the primary key, the second field is the assigned
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value:
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- = No Ownertrust value yet assigned.
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n = Never trust this keyholder to correctly verify others signatures.
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m = Have marginal trust in the keyholders capability to sign other
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keys.
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f = Assume that the key holder really knows how to sign keys.
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u = No need to trust ourself because we have the secret key.
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Keep these values confidential because they express your opinions
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about others. PGP stores this information with the keyring thus it
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is not a good idea to publish a PGP keyring instead of exporting the
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keyring. gnupg stores the trust in the trust-DB so it is okay to
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give a gpg keyring away (but we have a --export command too).
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7.4) What kind of output is this: "key C26EE891.298, uid 09FB: ...."?
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This is the internal representation of an user id in the trustdb.
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"C26EE891" is the keyid, "298" is the local id (a record number in
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the trustdb) and "09FB" is the last two bytes of a ripe-md-160 hash
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of the user id for this key.
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7.5) How do I interpret some of the informational outputs?
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While checking the validity of a key, GnuPG sometimes prints some
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information which is prefixed with information about the checked
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item. "key 12345678.3456" This is about the key
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with key ID 12345678 and the internal number 3456, which is the
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record number of the so called directory record in the trustdb.
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"uid 12345678.3456/ACDE" This is about the user ID for
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the same key. To identify the user ID the last two bytes of a
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ripe-md-160 over the user ID ring is printed. "sig
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12345678.3456/ACDE/9A8B7C6D" This is about the signature
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with key ID 9A8B7C6D for the above key and user ID, if it is a
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signature which is direct on a key, the user ID part is empty
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(..//..).
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7.6) Are the header lines of a cleartext signature part of the signed
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material?
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No. For example you can add or remove "Comment:" lines. They have
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a purpose like the mail header lines. However a "Hash:" line is
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needed for OpenPGP signatures to tell the parser which hash
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algorithm to use.
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2001-03-16 11:03:43 +00:00
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7.7) What is the list of preferred algorithms?
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2001-07-12 12:44:48 +00:00
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The list of preferred algorithms is a list of cipher, hash and
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2001-03-16 11:03:43 +00:00
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compression algorithms stored in the self-signature of a key during
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key generation. When you encrypt a document, GnuPG uses this list
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(which is then part of a public key) to determine which algorithms
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to use. Basically it tells other people what algorithms the
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recipient is able to handle and provides an order of preference.
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7.8) How do I change the list of preferred algorithms?
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2001-08-30 16:39:23 +00:00
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Use the edit menu and set the new list of preference using the
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command "setpref"; the format of this command resembles the output
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of the command "pref". The preference are not changes immediately
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but the set preference will be used when a new user ID is
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created. If you want to update the preferences for existing user
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IDs, select those user IDs (or select none to update all) and
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enter the command "updpref". Note that the timestamp of the
|
2001-09-13 16:26:00 +00:00
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self-signatures is increaded by one second when running this
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2001-08-30 16:39:23 +00:00
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command.
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2000-09-14 12:20:30 +00:00
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8. ACKNOWLEDGEMENTS
|
1998-10-06 12:10:02 +00:00
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2000-09-14 12:20:30 +00:00
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Many thanks to Werner Koch for the original FAQ file and to all
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posters to gnupg-users and gnupg-devel. They all provided most of
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the answers.
|
1998-10-06 12:10:02 +00:00
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2000-09-14 12:20:30 +00:00
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Also thanks to Casper Dik for providing me with a script to generate
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this FAQ (he uses it for the excellent Solaris2 FAQ).
|
1998-10-06 12:10:02 +00:00
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2000-09-14 12:20:30 +00:00
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Copyright (C) 2000 Free Software Foundation, Inc. ,
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59 Temple Place - Suite 330, Boston, MA 02111, USA
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2000-01-14 17:26:00 +00:00
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2000-09-14 12:20:30 +00:00
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Verbatim copying and distribution of this entire article is permitted in
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any medium, provided this notice is preserved.
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