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G10 - The GNU Encryption and Signing Tool
------------------------------------------
THIS IS VERSION IS ONLY A TEST VERSION ! YOU SHOULD NOT
USE IT FOR OTHER PURPOSES THAN EVALUATING THE CURRENT CODE.
* The data format may change in the next version!
* Some features are not yet implemented
I provide this version as a reality check to start discussion.
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 G10 does not use use any patented algorithm,
it cannot be compatible to old PGP versions, because those use
IDEA (which is worldwide patented) 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, G10 is not yet
compatible to it (or PGP 5) - but it will. The data structures
used are compatible with PGP 2.x, so it can parse an list such files
and PGP should be able to parse data created by G10 and complain
about unsupported algorithms.
The default algorithms used by G10 are ElGamal for public-key
encryption and signing; Blowfish with a 160 bit key for protecting
the secret-key components, conventional and session encryption;
RIPE MD-160 to create message digest. DSA, SHA-1 and CAST are
also implemented, but not used on default. I decided not
to use DSA as default signing algorithm, because it allows only for
1024 bit keys and this may be not enough in a couple of years.
Installation
------------
1) "./configure"
to enable the integrated malloc debugging stuff, use:
"./configure --enable-m-debug"
2) "make"
3) "make install"
4) You end up with a binary "g10" in /usr/local/bin
Resources
---------
G10 needs a directory "~/.g10" to store the default keyrings
and other files.
Key Generation
--------------
g10 --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 emit only bytes if the kernel can gather enough entropy.
If you see no progress, you should start some other activities such
as mouse moves or a "find /". Because we have no hardware device
to generate random we have to use this method.
Key generation shows progress by printing different characters to
stderr:
"." Miller-Rabin test failed.
"+" Miller-Rabin test succeeded.
"!" Reloading the pool with fresh prime numbers
"^" Checking a new value for the generator
"~" Issued during generator checks
"<" 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 number, 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 can sign a key with this command:
g10 --sign-key Donald
To sign the key of of "Donald" with your default userid
g10 --sign-key -u Karl -u Joe Donald
To 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 the you are asked for every user
wether you want to sign this key.
You may remove a signature at any time by usiing the option "--edit-sig",
which also asks for the sigs to remove.
Sign
----
g10 -s file
This creates a file file.g10 which is compressed and has a signature
attached.
g10 -sa file
Same as above, but file.g10 is ascii armored.
g10 -s -o out file
Creates a signature of file, but writes the output to the file "out".
Encrypt
-------
g10 -e -r heine file
This encrypts files with the public key of "heine" and writes it
to "file.g10"
echo "hallo" | g10 -ea -r heine | mail heine
Ditto, but encrypts "hallo\n" and mails it as ascii armored message.
Sign and Encrypt
----------------
g10 -se -r heine file
This encrypts files with the public key of "heine" and writes it
to "file.g10" after signing it with the default user id.
g10 -se -r heine -u Suttner file
Ditto, but sign the file with the user id "Suttner"
Examine a data or key file
--------------------------
g10 --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 G10 is able to look at the
inner structure of a encrypted packet.
Batch mode
----------
If you use the option "--batch", G10 runs in non-interactive mode and
never prompts for input data. This even does not allow to enter
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 PGP to terminate as soon as a BAD signature is
detected.
Exit status
-----------
G10 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 to get detailed informations about the errors.
Debug Flags
-----------
Use the option "--debug n" to output debug informations. 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
Other Notes
-----------
This is work in progress, so you may find duplicated code fragments,
ugly data structures, weird usage of filenames and other thinks.
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/g10.html"
Please direct bug reports to <g10-bugs@isil.d.shuttle.de> or better
post them to the mailing list <g10@net.lut.ac.uk>.
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