path: root/README

		  GNUPG - The GNU Privacy Guard
		 -------------------------------

    THIS IS ALPHA SOFTWARE, YOU MAY ENCOUNTER SOOME 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 is not yet
    compatible with it (or PGP 5) - but it will be.  The data structures
    used are compatible with PGP 2.x, so it can parse and list such files
    and PGP should be able to parse data created by GNUPG and complain
    about unsupported algorithms.

    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.

    Key generation shows progress by printing different characters to
    stderr:
	     "."  Last 10 Miller-Rabin tests failed
	     "+"  Miller-Rabin test succeeded
	     "!"  Reloading the pool with fresh prime numbers
	     "^"  Checking a new value for the generator
	     "<"  Size of one factor decreased
	     ">"  Size of one factor increased

    The prime number for ElGamal is generated this way:

    1) Make a prime number q of 160, 200, 240 bits (depending on the keysize)
    2) Select the length of the other prime factors to be at least the size
       of q and calculate the number of prime factors needed
    3) Make a pool of prime numbers, each of the length determined in step 2
    4) Get a new permutation out of the pool or continue with step 3
       if we have tested all permutations.
    5) Calculate a candidate prime p = 2 * q * p[1] * ... * p[n] + 1
    6) Check that this prime has the correct length (this may change q if
       it seems not to be possible to make a prime of the desired length)
    7) Check whether this is a prime using trial divisions and the
       Miller-Rabin test.
    8) Continue with step 4 if we did not find a prime in step 7.
    9) Find a generator for that prime.

    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.


    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>.