Digest::SipHash

A Ruby implementation of SipHash with optional Rust native extension. Supports SipHash 1-3, 2-4 or arbitrary round counts. Defaults to SipHash 1-3 with 16 null bytes as the key.

What is SipHash?

SipHash is a fast, cryptographically strong pseudorandom function optimized for short inputs.

Requirements

• Ruby 3.0+
• Optional: Rust 2024+ edition (automatic native extension compilation)

Installation

gem install digest-sip_hash

Quick Start

require 'digest/sip_hash'

# Basic usage with default settings (SipHash 1-3)
Digest::SipHash.hexdigest 'hello world'
#=> "421ga35b9c80c1c4"

# Use a secret key for authentication
require 'securerandom'
secret = SecureRandom.random_bytes(16)
Digest::SipHash.new(key: secret).hexdigest 'message'
#=> "a4d2f8b6e3c91d7f"

# SipHash 2-4 variant
Digest::SipHash24.hexdigest 'hello world'
#=> "5ee588584e5b2333"

Performance

When Rust is available the native extension builds automatically and dramatically improves runtime performance. On my machine the native extension is:

• More than 10x faster with an 8 byte messages
• More than 1,000x faster with a 4,096 byte messages

The gem gracefully falls back to pure Ruby if the native extension fails to build.

Detailed Examples

Standard Variants

# SipHash 1-3 (default: 1 compression round, 3 finalization rounds)
Digest::SipHash.hexdigest ''
#=> "d1fba762150c532c"

Digest::SipHash13.hexdigest ''
#=> "d1fba762150c532c"

# SipHash 2-4 (original specification)
Digest::SipHash24.hexdigest ''
#=> "1e924b9d737700d7"

Digest::SipHash.new(2, 4).hexdigest ''
#=> "1e924b9d737700d7"

Custom Round Counts

# Higher security with more rounds
Digest::SipHash.new(4, 8).hexdigest ''
#=> "23ec6dd806738af3"

Digest::SipHash.new(8, 16).hexdigest ''
#=> "c05e9233091eb559"

Using Custom Keys

# Default key (16 null bytes)
Digest::SipHash.new(key: 0.chr * 16).hexdigest ''
#=> "d1fba762150c532c"

# Custom key
Digest::SipHash.new(key: 16.times.map(&:chr).join).hexdigest ''
#=> "abac0158050fc4dc"

# Secure random key
require 'securerandom'
secret = SecureRandom.random_bytes(16)
digest = Digest::SipHash.new(key: secret)
digest.hexdigest 'message'
#=> "dd854240c470edef"

Incremental Hashing

digest = Digest::SipHash.new
digest << 'hello'
digest << ' '
digest << 'world'
digest.hexdigest
#=> "421ga35b9c80c1c4"

Command Line Examples

Usage: siphash [OPTIONS] FILE
    -c=ROUNDS                        Number of c rounds. Default: 1
    -d=ROUNDS                        Number of d rounds. Default: 3
    -k, --key=KEY                    Sixteen-byte hex key. Default: "00000000000000000000000000000000"

Check hashes by providing a filename to the siphash executable:

touch empty_file
siphash empty_file
#>> d1fba762150c532c  empty_file

Or pipe input to siphash:

# SipHash 1-3
echo -n "" | siphash
#>> d1fba762150c532c  -

# SipHash 2-4
echo -n "" | siphash -c2 -d4
#>> 1e924b9d737700d7  -

echo -n "" | siphash --key "00010203040506070809101112131415"
#>> 067c02f6c87ccd93  -

Alternatives

• Pure C extension: digest-siphash

License

MIT