ScatterSwap

Elixir implementation of Nathan and David Amick's Scatter Swap.

ScatterSwap implements an integer hash function designed to have zero collisions, achieve avalanche, and be reversible.

The goal is to transform an integer into another random looking integer and then reliably tranform it back.

It will turn the number 3 into 2356513904, and it can then reliably reverse that scrambled 2356513904 number back into 3

We also want sequential integers to become non-sequential.

So for example it will turn 7001, 7002, 7003 into 5270192353, 7107163820, 3296163828, and back again.

Please note, this is not encryption or related to security in any way. It lightly obfuscates an integer in a reversable way.

Hashing

iex> ScatterSwap.hash(3)
2057964173
iex> ScatterSwap.hash(7001)
2037964193
iex> ScatterSwap.hash(7002)
3613429027
iex> ScatterSwap.hash(7003)
677313294

Reverse Hashing

iex> ScatterSwap.reverse_hash(2037964193)
7001
iex> ScatterSwap.reverse_hash(3613429027)
7002
iex> ScatterSwap.reverse_hash(677313294)
7003

Spin

A second argument spin can be passed to each of ScatterSwap.hash/2 or ScatterSwap.reverse_hash/2, as a seed to alter the hashing process.

iex(8)> ScatterSwap.hash(123)
2059944173
iex(9)> ScatterSwap.hash(123, 1)
3480094612
iex(10)> ScatterSwap.hash(123, 2)
6571025309
iex(11)> ScatterSwap.hash(123, 728283)
9180174562

iex> ScatterSwap.reverse_hash(2059944173)
123
iex> ScatterSwap.reverse_hash(3480094612, 1)
123
iex> ScatterSwap.reverse_hash(6571025309, 2)
123
iex> ScatterSwap.reverse_hash(9180174562, 728283)
123

Limitations

This library is built for integers which can be expressed in 10 digits. The largest number it can deal with is 10 Billion - 1:

9999999999

Differences from the Ruby Implementation

Whereas the Ruby version returns zero-padded strings, this implementation returns integers.

How it Works

Please see the README for Nathan and David Amick's Ruby implementation of Scatter Swap for more information on the hashing algorithm itself.

Contributing

Source repository is at https://github.com/dougal/scatter_swap.ex, please file issues and pull requests there.

Installation

The package can be installed by adding scatter_swap to your list of dependencies in mix.exs:

def deps do
  [{:scatter_swap, "~> 0.1.0"}]
end

Documentation

Documentation can be found online at HexDocs.

Alternatively, you can generate docs from the project root with:

mix docs

Copyright and Licence

Copyright (c) 2017, Douglas F Shearer.

ScatterSwap is licensed under the MIT Licence.