secret-base62

Generate random token using base62 which is alphanumeric with uppercase and lowercase.

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

You can test my image on DockerHub:

docker run evanxsummers/secret-base62

It should output a random base62 string e.g. r2CKLsQ4HxfFevdl

It is implemented as follows:

const assert = require('assert');
const crypto = require('crypto');
const digits = '0123456789';
const letters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
const charset = [digits, letters, letters.toLowerCase()].join('');
assert.equal(charset.length, 62);
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:

0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz

We can build using its Dockerfile as follows:

docker build -t secret-base62 https://github.com/evanx/secret-base62.git

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

docker run -t secret-base62

which gives random output e.g. zQPv2WXCuy43nueh

Use length envar to change from default 16

docker run -e length=32 secret-base62

which outputs length 32 token e.g. CMZRUgDU5RxwzhDFh7fV5EKAKz6HmXdb

Related

• https://github.com/evanx/secret-base26
• https://github.com/evanx/secret-base32
• https://github.com/evanx/secret-base36
• https://github.com/evanx/secret-base56