secret-base56

Randomly generate a secret token using base56 charset i.e. alphanumeric upper and lower omitting letters I and O and digits zero and one.

We omit those characters to avoid potential confusion if transcribed by humans e.g. for hand-written backup.

This is suitable for secret URLs, whereas base64 includes slash in its charset.

Incidently, my personal use case is for Telegram.org webhook secrets - see https://github.com/evanx/webhook-publish

You can test my image on DockerHub:

docker run evanxsummers/secret-base56

It should output a random base56 string e.g. r2CKLsQ4HxfFevdl

It is implemented as follows:

const assert = require('assert');
const crypto = require('crypto');
const letters24 = 'ABCDEFGHJKLMNPQRSTUVWXYZ'; // exclude I and O since too similar to 0 and 1
const digits8 = '23456789'; // omit 0 and 1 to avoid potential confusion with O and I (and perhaps 'l')
const charset = [digits8, letters24, letters24.toLowerCase()].join('');
assert.equal(charset.length, 56);
const length = parseInt(process.env.length || '16');
const string = crypto.randomBytes(length)
.map(value => charset.charCodeAt(Math.floor(value*charset.length/256)))
.toString();
console.log(string);

where we generate an array of random bytes (values 0 to 255 inclusive) of the desired length and then map each into our charset:

23456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghjklmnpqrstuvwxyz

We can build using its Dockerfile as follows:

docker build -t secret-base56 https://github.com/evanx/secret-base56.git

where we tag the image so we can run by tag name:

docker run -t secret-base56

which gives random output e.g. zQPv2WXCuy43nueh

Use length envar to change from default 16

docker run -e length=32 secret-base56

which outputs length 32 token e.g. CMZRUgDU5RxwzhDFh7fV5EKAKz6HmXdb

You can then use this for a secret URL e.g. for a Telegram Bot webhook, or some other purpose.

Related

See the following related project which is case-insensitive base32.

https://github.com/evanx/secret-base32

Base32 is better for hand-written backups since some letters have similar shapes in lowercase e.g. c, s, u, v