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What is it?

SleepingKangaroo12 is a Ruby binding of KangarooTwelve, a fast cryptographic hash function by the team behind SHA-3.

Why not SHA-3?

SHA-3 is relatively slow without special function hardware, partly due to NIST, the organizer of the SHA-3 competition, requested for a huge security margin from the candidates.

The team behind Keccak, the winner of the SHA-3 competition, feels that SHA-3 is not at the sweet spot between trade-offs; they release a more performant, one-size-fit-all hash algorithm building on top of SHA-3 primitives, the KangarooTwelve.

Instead of making the function tunable like Keccak, they opinionatedly select the parameter for KangarooTwelve, so there is one and only one KangarooTwelve variant.

Why Sleeping?

Other Ruby bindings existed before mine; I added the adjective to distinguish mine. Furthermore, I wrote this binding in pajamas, and I don't expect that I'll have the need to update this gem. From your perspective, it might look as if the gem is sleeping. :-D

What are specials?

  • It builds on top of the K12, an easy-to-use and highly optimized library maintained by the Keccak team themselves.
  • The instruction set AVX512, AVX2, and SSSE3 will be detected at runtime to select the optimization dynamically.
  • Thin and stable binding layer
  • Not limited to Matz's Ruby Interpreter (MRI), this is due to the gem opting for Ruby-FFI instead of using the API exposed by ruby.h. (I only tested on MRI, though.)


In order to install the gem, your machine should be ready to build the K12 package. Which mean you should prepare:

  • GCC, the GNU Compiler Collection; our favorite
  • GNU make
  • xsltproc executable, normally comes with libxslt package
  • Ruby related stuffs

TL;DR for Ubuntu-liked OS

sudo apt install build-essential xsltproc


Add this line to your application's Gemfile:

gem 'sleeping_kangaroo12'

Check the prerequisites; and then execute:

$ bundle install

Usage Examples

Test vectors stolen from konsolebox/digest-kangarootwelve-ruby, another Ruby binding.

# basic usage
# => "ab174f328c55a5510b0b209791bf8b60e801a7cfc2aa42042dcb8f547fbe3a7d"

# streaming
digest =
digest << 'a'
digest << 'b'
digest << 'c'
# => "ab174f328c55a5510b0b209791bf8b60e801a7cfc2aa42042dcb8f547fbe3a7d"
# `<<` is an alias of `update`, use the one you like

# keyed hash (AKA: customization)
digest = 'secret')
digest << 'abc' # alternate form of update method
# => "dc1fd53f85402e2b34fa92bd87593dd9c3fe6cc49d9db6c05dc0cf26c6a7e03f"

# shortcuts
# => "\xAB\x17O2\x8CU\xA5Q\v\v \x97\x91\xBF\x8B`\xE8\x01\xA7\xCF\xC2\xAAB\x04-\xCB\x8FT\x7F\xBE:}"
::SleepingKangaroo12::Digest.hexdigest('abc', key: 'secret')
# => "dc1fd53f85402e2b34fa92bd87593dd9c3fe6cc49d9db6c05dc0cf26c6a7e03f"
::SleepingKangaroo12::Digest.base64digest('abc', output_length: 24)
# => "qxdPMoxVpVELCyCXkb+LYOgBp8/CqkIE"
# `digest`, `hexdigest`, and `base64digest` are available as shortcuts and also on `Digest` instances.
# Same for the options, you may use `key`, `key_seed`, and `output_length` on both instance methods and shortcuts

# XOF (extendable-output functions)
digest = 64)
digest << 'abc'
# => "ab174f328c55a5510b0b209791bf8b60e801a7cfc2aa42042dcb8f547fbe3a7d3f5b54d116a705d36aac2a7eac7a19e3f0f058cb3c238ac7f034178ae34f212e"

# weird parameters 'secret', output_length: 1_000_000_000_000)
# error: Hash length out of range (ArgumentError)
# I arbitrary set the limit of output length at 1MiB - 1 bytes as a safety measure. Same for length <= 0
# If you have a use case for something out of range, feel free to discuss.

About CPU Throttling

At the time of this writing, if you use a lot of AVX-512, your CPU would heat up significantly; this leads to frequency throttling.

If you plan to use KangarooTwelve heavily yet still have other functionalities impacted by lower CPU frequencies (like Cloudflare), you may want to customize the build to prevent the throttling.

If that is the case, please check konsolebox/digest-kangarootwelve-ruby. At the time of this writing, they offer customizable build; in contrast, SleepingKangaroo12 will focus on ease of use.


SleepingKangaroo12 is released under the BSD 3-Clause License. 🎉