diceware 0.1

Install

This Python package can be installed via pip:

$ pip install diceware

The exact way depends on your operating system.

Usage

Once installed, use --help to list all available options:

$ diceware --help
usage: diceware [-h] [-n NUM] [-c | --no-caps] [-s NUM]

Create a passphrase

optional arguments:
  -h, --help            show this help message and exit
  -n NUM, --num NUM     number of words to concatenate. Default: 6
  -c, --caps            Capitalize words. This is the default.
  --no-caps             Turn off capitalization.
  -s NUM, --specials NUM
                        Insert NUM special chars into generated word.

With -n you can tell how many words are supposed to be picked for your new passphrase:

$ diceware -n 1
Thud

$ diceware -n 2
KnitMargo

You can diceware additionally let generate special chars to replace characters in the ‘normal’ passphrase. The number of special chars generated can be determined with the -s option (default is zero):

$ diceware -s 2
Heroic%unkLon#DmLewJohns

Here "%" and "#" are the special chars.

Special chars are taken from the following list:

~!#$%^&*()-=+[]\{}:;\"'<>?/0123456789

Please note that several special chars might replace the same original char, resulting in a passphrase with less special chars than requested.

By default the single phrase words are capitalized, i.e. the first char of each word is made uppercase. This does not neccessarily give better security (1 bit at most), but it helps reading a phrase.

You can nevertheless disable caps with the --no-caps option:

$ diceware --no-caps
oceanblendbaronferrylistenvalet

This leads to lower-case passphrases, maybe easier to type on smart phones or similar.

What is it good for?

Normally, diceware passphrases are easier to remember than shorter passwords constructed in more or less bizarre ways. But at the same time diceware passphrases provide more entropy as xkcd can show with the famous ‘936’ proof:

The standard english wordlist of this diceware implementation contains 8192 == 2**13 different english words. It is a copy of the Diceware8k list provided by Mr. Reinhold. Therefore, picking a random word from this list gives an entropy of 13 bits. Picking six words means an entropy of 6 x 13 == 73 bits.

The special chars replacing chars of the originally created passphrase give some more entropy (the more chars you have, the more additional entropy), but not much. For instance, for a sixteen chars phrase you have sixteen possibilities to place one of the 36 special chars. That makes 36 x 16 possibilitities or an entropy of about 9.17 you can add. To get an entropy increase of at least 10 bits, you have to put a special char in a phrase with at least 29 chars (while at the same time an additional word would give you 13 bits of extra entropy). Therefore you might think again about using special chars in your passphrase.

Is it secure?

The security level provided by Diceware depends heavily on your source of random. If the delivered randomness is good, then your passphrases will be very strong. If instead someone can foresee the numbers generated by a random number generator, your passphrases will be surprisingly weak.

This Python implementation uses the random.SystemRandom source provided by Python. On Un*x systems it accesses /dev/urandom. You might want to follow reports about manipulated random number generators in operating systems closely.

The Python API of this package allows usage of other sources of randomness when generating passphrases.

Developer Install

Developers want to fork me on github:

$ git clone https://github.com/ulif/diceware.git

We recommend to create and activate a virtualenv first:

$ cd diceware/
$ virtualenv -p /usr/bin/python3.3 py33
$ source py33/bin/activate
(py33) $

We support Python versions 2.6, 2.7, 3.2, 3.3, 3.4, pypy.

Now you can create the devel environment:

(py33) $ python setup.py dev

This will fetch test packages (py.test). You should be able to run tests now:

(py33) $ py.test

If you have also different Python versions installed you can use tox for using them all for testing:

(py33) $ pip install tox   # only once
(py33) $ tox

Should run tests in all supported Python versions.

(py33) $ python setup.py docs

(py33) $ cd docs/
(py33) $ make

Credits

Arnold G. Reinhold deserves all merits for the working parts of Diceware. The non-working parts are certainly my fault.

Links

• The Diceware home page. Reading definitely recommended!

• fork me on github

Wordlists:

• Diceware8k list by Arnold G. Reinhold.

License

This Python implementation of Diceware, (C) 2015 Uli Fouquet, is licensed under the GPL v3+.

The Copyright for the Diceware idea and the Diceware8k list are Copyright by Arnold G. Reinhold. See file LICENSE for details.