A Multihash implementation for ruby.

A multihash is a digest with an embedded hash function code (and length) ('cause you never know). It was developed primarily for use with IPFS, but is not specific to it.

Add this line to your application's Gemfile:

gem 'multihashes'

And then execute:

$ bundle

Or install it yourself as:

$ gem install multihashes

This is a low-level library. Bring your own digest. A binary digest goes in, a binary digest goes out. To compute a sha256 multihash that would work nicely with IPFS:

require 'multihashes'
require 'digest'

digest = Digest::SHA256.digest 'Dade Murphy will never figure this one out'
multihash_binary_string = Multihashes.encode digest, 'sha2-256'

multihash_binary_string.unpack('H*').first # hex: "1220142711d38ca7a33c521841..."

out = Multihashes.decode multihash_binary_string
# => {:code=>18, :hash_function=>"sha2-256", :length=>32, :digest=>"\x14'\x11\xD3\x8C\xA7\xA3<R\x18Ao\x8F\xFC\xC6FH\xCAF\x16\xA6%\xB5\xE0\xA0\xAB=\xA1\x91\x1D]z"}

Hash function names (latest is here)

code name
0x11 sha1
0x12 sha2-256
0x13 sha2-512
0x14 sha3
0x40 blake2b
0x41 blake2s
# 0x00-0x0f reserved for application specific functions
# 0x10-0x3f reserved for SHA standard functions

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install.

Bug reports and pull requests are welcome on GitHub at https://github.com/neocities/multihashes.

The gem is available as open source under the terms of the MIT License.