# colorhash

![Hash of the previous commit hash](examples/commithash.svg)

A tool for creating distinct art based on input data or hash.

# Usage

1. Clone the repository
2. Run using `python -m colorhash -h` for usage.

No dependencies required, everything is vanilla Python >=3.10.

## Example usage

### Create art using the default "nibble" art algorithm, printing out to the terminal

`python -m colorhash infile.dat`

### Create art using the OpenSSH "randomart" art algorithm, writing to an SVG file

`python -m colorhash infile.dat -y svg -o out.svg -m randomart`

### Create art using an MD5 hash instead of the default SHA512

`python -m colorhash infile.dat -y svg -o out.svg -a md5`

### Create art in the terminal using the current git commit hash

`python -m colorhash "$(git rev-parse HEAD)" -a sha1`

# Motivation

> If you see the picture is different, the key is different.
>
> If the picture looks the same, you still know nothing.

([From OpenSSH sshkey.c fingerprint_randomart() function](https://github.com/openssh/openssh-portable/blob/8054b906983ceaed01fabd8188d3dac24c05ba39/sshkey.c#L993))

Cryptographic hashes are often visually distinct, however, sometimes they are not. This can become
vitally important in matters of security, when you are comparing two key hashes or verifying the
checksum of a file from the internet. The goal of this project is to give more fuel for human
pattern recognition so that two extremely similar hashes, maliciously crafted or not, have more
visual depth to their distinction.

## Weaknesses

This is not a perfect solution for hash comparison. Similar hashes may just so happen to choose the
same color palette, for example. Additionally, if this is appearing on a webpage, caches may
override the most recent version of the file; this has happened with me and Chrome looking at the
Github page for this project.

Palette selection is questionable. It's mostly based on the hash itself, but the colors chosen are
sort of arbitrary, and certain color profiles are omitted based on the author's personal taste. For
example, the color palette for "light yellow" is omitted because it's hard to look at and
distinguish, while dark yellow is kept because it doesn't have that problem. If palettes are ever
removed or added in the future, this will have a cascading effect on palette selection, since this
is done by taking the sum of all of the bytes in the hash mod the number of palettes available. As
the software evolves, a colorhash made 5 years ago may have a different look today.

# Examples

See the examples directory.

# License

Code is licensed under GPLv3.

Since images are representation of a specific hash, all of the SVG files in the examples/ directory
are under CC0/public domain.