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GNUPG - The GNU Privacy Guard
-------------------------------
THIS IS ALPHA SOFTWARE, YOU MAY ENCOUNTER SOME BUGS.
On a Linux box (version 2.x.x, alpha or x86 CPU) it should
work reliably. You may create your key on such a machine and
use it. Please verify the tar file; there is a PGP and a GNUPG
signature available. My PGP key is well known and published in
the "Global Trust Register for 1998", ISBN 0-9532397-0-5.
I have included my pubring as "g10/pubring.asc", which contains
the key used to make GNUPG signatures:
"pub 1312G/FF3EAA0B 1998-02-09 Werner Koch <wk@isil.d.shuttle.de>"
"Key fingerprint = 8489 6CD0 1851 0E33 45DA CD67 036F 11B8 FF3E AA0B"
You may add it to your GNUPG pubring and use it in the future to
verify new releases. Because you verified the tar file containing
this file here, you can be sure that the above fingerprint is correct.
Please subscribe to g10@net.lut.ac.uk by sending a mail with
the word "subscribe" in the body to "g10-request@net.lut.ac.uk".
See the file COPYING for copyright and warranty information.
Due to the fact that GNUPG does not use use any patented algorithm,
it cannot be compatible with old PGP versions, because those use
IDEA (which is patented worldwide) and RSA (which is patented in
the United States until Sep 20, 2000). I'm sorry about this, but
this is the world we have created (e.g. by using proprietary software).
Because the OpenPGP standard is still a draft, GNUPG now interoperates
with it and PGP 5. The MUA Mutt will soon support GNUPG; it has a
mode to fallback to another program if the received message has been
created with RSA or IDEA.
The default algorithms used by GNUPG are ElGamal for public-key
encryption and signing; Blowfish with a 128 bit key for protecting
the secret-key components, conventional and session encryption;
RIPE MD-160 to create message digest. DSA, SHA-1, CAST and TIGER are
also implemented, but not used by default. I decided not
to use DSA as the default signing algorithm, because it allows only
for 1024 bit keys and this may not be enough in a couple of years.
Installation
------------
See the file INSTALL. Here is a quick summary:
1) "./configure"
2) "make"
3) "make install"
4) You end up with a binary "gpg" in /usr/local/bin
5) Optional, but suggested: install the program "gpg" as suid root.
Key Generation
--------------
gpg --gen-key
This asks some questions and then starts key generation. To create
good random numbers for prime number generation, it uses a /dev/random
which will only emit bytes if the kernel can gather enough entropy.
If you see no progress, you should start some other activities such
as mouse moves, "find /" or using the keyboard (in another window).
Because we have no hardware device to generate randomness we have to
use this method.
You should make a revocation certificate in case someone gets
knowledge of your secret key or you forgot your passphrase:
gpg --gen-revoke your_user_id
Run this command and store it away; output is always ASCII armored,
so that you can print it and (hopefully never) re-create it if
your electronic media fails.
If you decided to create a DSA key, you should add an ElGamal
for encryption:
gpg --add-key user_id_of_your_key
and follow the displayed instructions (select "ElGamal using v4 packets").
You can sign a key with this command:
gpg --sign-key Donald
This let you sign the key of "Donald" with your default userid.
gpg --sign-key -u Karl -u Joe Donald
This let you sign the key of of "Donald" with the userids of "Karl"
and "Joe".
All existing signatures are checked; if some are invalid, a menu is
offered to delete some of them, and then you are asked for every user
whether you want to sign this key.
You may remove a signature at any time using the option "--edit-sig",
which asks for the sigs to remove. Self-signatures are not removable.
Sign
----
gpg -s file
This creates a file file.gpg which is compressed and has a signature
attached.
gpg -sa file
Same as above, but file.gpg is ascii armored.
gpg -s -o out file
Creates a signature of file, but writes the output to the file "out".
Encrypt
-------
gpg -e -r heine file
This encrypts files with the public key of "heine" and writes it
to "file.gpg"
echo "hallo" | gpg -ea -r heine | mail heine
Ditto, but encrypts "hallo\n" and mails it as ascii armored message.
Sign and Encrypt
----------------
gpg -se -r heine file
This encrypts files with the public key of "heine" and writes it
to "file.gpg" after signing it with the default user id.
gpg -se -r heine -u Suttner file
Ditto, but sign the file with the user id "Suttner"
Keyring Management
------------------
To export your complete keyring(s) do this:
gpg --export
To export only some user ids do this:
gpg --export userids
Use "-a" or "--armor" to create ASCII armored output.
Importing keys is done with the option, you guessed it, "--import":
gpg --import [filenames]
New keys are appended to the default keyring and already existing
keys are merged. Keys without a self-signature are ignored.
How to Specify a UserID
-----------------------
There are several ways to specify a userID, here are some examples:
* Only by the short keyid (prepend a zero if it begins with A..F):
"234567C4"
"0F34E556E"
"01347A56A"
"0xAB123456
* By a complete keyid:
"234AABBCC34567C4"
"0F323456784E56EAB"
"01AB3FED1347A5612"
"0x234AABBCC34567C4"
* By a fingerprint:
"1234343434343434C434343434343434"
"123434343434343C3434343434343734349A3434"
"0E12343434343434343434EAB3484343434343434"
The first one is MD5 the others are ripemd160 or sha1.
* By an exact string (not yet implemented):
"=Heinrich Heine <heinrichh@uni-duesseldorf.de>"
* By an email address:
"<heinrichh@uni-duesseldorf.de>"
This can be used by a keyserver instead of a substring to
find this key faster.
* By the Local ID (from the trustdb):
"#34"
This can be used by a MUA to specify an exact key after selecting
a key from GNUPG (by the use of a special option or an extra utility)
* Or by the usual substring:
"Heine"
"*Heine"
The '*' indicates substring search explicitly.
Batch mode
----------
If you use the option "--batch", GNUPG runs in non-interactive mode and
never prompts for input data. This does not even allow entering the
passphrase; until we have a better solution (something like ssh-agent),
you can use the option "--passhrase-fd n", which works like PGPs
PGPPASSFD.
Batch mode also causes GNUPG to terminate as soon as a BAD signature is
detected.
Exit status
-----------
GNUPG returns with an exit status of 1 if in batch mode and a bad signature
has been detected or 2 or higher for all other errors. You should parse
stderr or the output of the fd specified with --status-fd to get detailed
information about the errors.
Esoteric commands
-----------------
gpg --list-packets datafile
Use this to list the contents of a data file. If the file is encrypted
you are asked for the passphrase, so that GNUPG is able to look at the
inner structure of a encrypted packet.
gpgm --list-trustdb
List the contents of the trustdb in a human readable format
gpgm --list-trustdb <usernames>
List the tree of certificates for the given usernames
gpgm --list-trust-path depth username
List the possible trust paths for the given username, up to the specified
depth. If depth is negative, duplicate introducers are not listed,
because those would increase the trust probability only minimally.
(you must use the special option "--" to stop option parsing when
using a negative number). This option may create new entries in the
trustdb.
gpgm --print-mds filenames
List all available message digest values for the fiven filenames
gpgm --gen-prime n
Generate and print a simple prime number of size n
gpgm --gen-prime n q
Generate a prime number suitable for ElGamal signatures of size n with
a q as largest prime factor of n-1.
gpgm --gen-prime n q 1
Ditto, but calculate a generator too.
For more options/commands see the file g10/OPTIONS, or use "gpg --help"
Debug Flags
-----------
Use the option "--debug n" to output debug information. This option
can be used multiple times, all values are ORed; n maybe prefixed with
0x to use hex-values.
value used for
----- ----------------------------------------------
1 packet reading/writing
2 MPI details
4 ciphers and primes (may reveal sensitive data)
8 iobuf filter functions
16 iobuf stuff
32 memory allocation stuff
64 caching
128 show memory statistics at exit
256 trust verification stuff
Other Notes
-----------
This is work in progress, so you may find duplicated code fragments,
ugly data structures, weird usage of filenames and other things.
I will run "indent" over the source when making a real distribution,
but for now I stick to my own formatting rules.
The primary FTP site is "ftp://ftp.guug.de/pub/gcrypt/"
The primary WWW page is "http://www.d.shuttle.de/isil/crypt/gnupg.html"
If you like, send your keys to <gnupg-keys@isil.d.shuttle.de>; use
"gpg --export --armor | mail gnupg-keys@isil.d.shuttle.de" to do this.
Please direct bug reports to <gnupg-bugs@isil.d.shuttle.de> or better
post them to the mailing list <g10@net.lut.ac.uk>.