Gem Version Build status Code Climate Inline Docs

Sixword implements the 6-word binary encoding created for S/Key (tm) and standardized by RFC 2289, RFC 1760, and RFC 1751. Binary data may be encoded using a dictionary of 2048 English words of 1-4 characters in length. Each block of 64 bits is encoded using 6 words, which includes 2 parity bits. It is ideal for transmitting binary data such as cryptographic keys where humans must communicate or enter the values.

Comparison to other encodings

See also: Bubble Babble, PGP Word List, Diceware, Base64, Base32

  • Bubble Babble does not use full words, so it is more difficult for humans to type or communicate over the phone.

  • The PGP Word List is optimized for communicating fingerprints, so it uses much longer and more distinct words. This is less convenient when you actually expect a human to type the whole sentence. Sixword handles error detection with the built-in parity bits.

  • Diceware is optimized for creating passphrases by a roll of standard 6-sided dice, so it uses a word list that is a power of 6. This is not very convenient as an encoding for arbitrary binary data.

  • Base64 is well suited as a machine encoding where an ASCII transport is desired. It is not very convenient for humans, and has no parity built in.

  • Base32 is somewhat better for humans than Base64 because it is case insensitive and doesn't include 0 or 1. However it is still not very convenient for humans to type or visually inspect.


Add this line to your application's Gemfile:

gem 'sixword'

And then execute:

$ bundle

Or install it yourself as:

$ gem install sixword

Usage: Command Line

Sixword operates similarly to base64(1), it operates on a file or on STDIN in two modes:

  • encode: accept binary data (or hexadecimal in hex modes) and print six-word encoded data on stdout.
  • decode: accept six-word encoded data and print binary data (or hex) on stdout.


Normal encoding and decoding

$ sixword <<< 'Testing'

$ sixword -d <<< 'BEAK NET SITE ROTH SWIM FORM'

$ sixword -d <<< 'beak net site roth swim form'

The same data, but hex encoded

$ sixword -H <<< '54:65:73:74:69:6e:67:0a'

$ sixword -dH <<< 'BEAK NET SITE ROTH SWIM FORM'

$ sixword -df <<< 'BEAK NET SITE ROTH SWIM FORM'
5465 7374 696E 670A

$ sixword -d -S colons <<< 'BEAK NET SITE ROTH SWIM FORM'

Error handling

$ sixword -d <<< 'BEAK NET SITE ROTH SWIM FOR'
sixword: Parity bits do not match
[exit status 3]

$ sixword -p <<< '.'
sixword: Must pad bytes to multiple of 8 or use pad_encode

Usage: Library

See the YARD documentation. The top-level Sixword module contains the main API (Sixword.encode and Sixword.decode), while various utilities can be found in Sixword::Hex and Sixword::Lib. Most of the code powering the command line interface is in Sixword::CLI.

>> require 'sixword'

>> Sixword.encode('Hi world')
=> ["ACRE", "ADEN", "INN", "SLID", "MAD", "PAP"]

>> Sixword.decode(["ACRE", "ADEN", "INN", "SLID", "MAD", "PAP"])
=> 'Hi world'

>> Sixword.decode("acre aden inn slid mad pap")
=> 'Hi world'


  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request