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ruby-multihash

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.

Install

Add this line to your application's Gemfile:

gem 'multihashes'

And then execute:

$ bundle

Or install it yourself as:

$ gem install multihashes

Usage

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

Development

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.

Maintainers

@kyledrake

Contribute

Bug reports and pull requests are welcome on GitHub at https://github.com/multiformats/ruby-multihash.

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.