The Keccak (SHA3) digest for Ruby

This Ruby extension exposes the Keccak (SHA3) digest C bindings in the non-final version used by Ethereum. It is based on the reference C implementation, version 3.2. The exposed interface is almost identical to that of the digest standard library. See #16.

⚠️ Note: version ~> 1.3 exposes digest/keccak (Digest::Keccak) whereas version ~> 1.2 maintains the old digest/sha3 (Digest::SHA3) for backward compatibility. Only use ~> 1.2 if you want to lazy-patch your library. It works, but it's not recommended. Use ~> 1.3 and simply rename SHA3 to Keccak.

Installation

The gem is called keccak.

bundle add keccak
gem install keccak

gem 'keccak', '~> 1.3'

Note: as of version ~> v1.1, digest-sha3 (historic name, see below) requires Ruby 2.2. The new keccak version ~> v1.2 now also supports Ruby 3.0. The last version that worked on older Ruby (1.x) versions was ~> v1.0. It can be found at the no longer maintained digest-sha3 repository from 2015.

Usage

This gem extends the digest/* module by a digest/keccak class.

require 'digest/keccak'

# Generate 512-bit digest.
Digest::Keccak.digest("foo")       # => "\025\227\204*..."
Digest::Keccak.hexdigest("foo")    # => "1597842a..."

# Generate 224-bit digest.
Digest::Keccak.digest("foo", 224)       # => "\332\251M\247..."
Digest::Keccak.hexdigest("foo", 224)    # => "daa94da7..."

# Use this interface to feed data in chunks. 512-bit by default.
digest = Digest::Keccak.new
digest.update("f")
digest.update("o")
digest.update("o")
digest.digest       # => "\025\227\204*..."
digest.hexdigest    # => "1597842a..."

# You can pass a hash length to the constructor.
digest = Digest::Keccak.new(224)

Keccak supports five hash lengths: 224-bit, 256-bit, 384-bit, 512-bit and variable length. Variable length is not supported by this Ruby extension. Unless the user specifies otherwise, this Ruby extension assumes 512-bit.

Running the test suite

Run the test suite as follows:

bundle install
make test

A part of the test suite is automatically generated from Keccak's reference test suite.

Warning: Keccak vs. SHA3

Note: This gem still uses the Digest::SHA3 namespace in version ~> 1.2 for reasons of backward compatibility and long-term maintainability. See history section below.

⚠️ This gem does not implement the final FIPS202 standard, today known as SHA3 but rather an early version, commonly referred to as Keccak. The reason why this is kept around, is that Ethereum uses this earler version of Keccak. See also: Ethereum: Difference between keccak256 and sha3.

If you are looking for the final SHA3 gem, please use the following: https://rubygems.org/gems/sha3

History

This gem was initially developed and published as digest-sha3: https://github.com/phusion/digest-sha3-ruby

This gem was later patched multiple times:

• https://github.com/teamhedge/digest-sha3-ruby (KECCAK, as digest-sha3-patched)
• https://github.com/sydneyitguy/digest-sha3-ruby (KECCAK, as digest-sha3-patched-ruby-3)
• https://github.com/steakknife/digest-sha3-ruby (actual SHA3, do not use for Ethereum)
• https://github.com/kotovalexarian/digest-keccak/ (KECCAK, as digest-keccak)