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 " "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 " * By an email address: "" 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 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 ; use "gpg --export --armor | mail gnupg-keys@isil.d.shuttle.de" to do this. Please direct bug reports to or better post them to the mailing list .