Travis CI

A simple 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, current multicodec is here)

code name comment
0x00 identity raw binary
0x11 sha1
0x12 sha2-256
0x13 sha2-512
0x14 sha3-512
0x15 sha3-384
0x16 sha3-256
0x17 sha3-224
0x18 shake-128
0x19 shake-256
0x1a keccak-224 keccak has variable output length. The number specifies the core length
0x1b keccak-256
0x1c keccak-384
0x1d keccak-512
0x22 murmur3-128
0x23 murmur3-32
0x56 dbl-sha2-256
0xd4 md4
0xd4 md5
0xd6 bmt Binary Merkle Tree Hash
0x1100 x11
0xb201 blake2b-8 blake2b consists of 64 output lengths that give different hashes
0xb202 blake2b-16
0xb203 blake2b-24
0xb23f blake2b-504
0xb240 blake2b-512
0xb241 blake2s-8 blake2s consists of 32 output lengths that give different hashes
0xb242 blake2s-16
0xb243 blake2s-24
0xb25f blake2s-248
0xb260 blake2s-256
0xb301 skein256-8 skein256 consists of 32 output lengths that give different hashes
0xb302 skein256-16
0xb303 skein256-24
0xb31f skein256-248
0xb320 skein256-256
0xb321 skein512-8 skein256 consists of 32 output lengths that give different hashes
0xb322 skein512-16
0xb323 skein512-24
0xb35f skein512-504
0xb360 skein512-512
0xb361 skein1024-8 skein1024 consists of 128 output lengths that give different hashes
0xb362 skein1024-16
0xb363 skein1024-24
0xb3df skein1024-1016
0xb3e0 skein1024-1024


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

Check out our contributing document for more information on how we work, and about contributing in general. Please be aware that all interactions related to multiformats are subject to the IPFS Code of Conduct.

Small note: If editing the README, please conform to the standard-readme specification.


The gem is available as open source under the terms of the MIT License © 2015 Kyle Drake.