Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with
or
.
Download ZIP
Estimate the entropy of a passphrase.
Ruby
branch: master

Fetching latest commit…

Cannot retrieve the latest commit at this time

Failed to load latest commit information.
lib
test
.gitignore
README.md
Rakefile
passphrase_entropy.gemspec

README.md

PassphraseEntropy

Estimate the entropy of a passphrase. This is calculated as the number of bytes required to encode the passphrase on top of a Deflate stream of a preset dictionary.

Inspired by xkcd 936.

Usage

require "passphrase_entropy"

pe = PassphraseEntropy.new
# or customise the dictionary:
pe = PassphraseEntropy.new(File.read("/usr/share/dict/words"))

pe.entropy("password") # => 6
pe.entropy("correct horse battery staple") # => 24
pe.entropy("Tr0ub4dor&3") # => 21

You can decide on your acceptable level of complexity.

Notes

It's a bit slow: the dictionary must be deflated every time. This could be ameliorated by saving the state, but that would require a modified zlib library. (It's easy to do with a pure Ruby zlib library, but Ruby is so much slower in this case that the overall gain in speed is almost zero.)

Tested using the web2 dictionary installed in Ubuntu Linux by:

apt-get install dictionaries-common miscfiles

Results will vary depending on the dictionary used.

Something went wrong with that request. Please try again.