This is designed to generate a string from a number so that it can be displayed to a user without similar numbers being easy to guess. It is generally used in creating URLs that map to IDs.

This code was ported from my Perl module at https://github.com/CliffS/crypt-pseudo. The code was originally ported from the PHP at https://blog.kevburnsjr.com/php-unique-hash (now defunct).

npm install pseudohash

assert = require('assert');
Pseudo = require('pseudohash');
var pseudo = new Pseudo(62);

var number = Math.floor(Math.random() * 100000);
var hash = pseudo.hash(number, 5);
console.log(hash);

var newnum = pseudo.unhash(hash);
assert.equal(newnum, number);

The new Pseudo() command creates a "factory" for generating pseudo-hashes. Yuo can choose between 62 bit hashes (using A to Z, a to z, 0 to 9) and 36 bit hashes (using upper-case letters and digits only). It defaults to 62 bits if no value is passed.

The hash() routine can be passed a length. This is the length of the resulting pseudo-hash, defaulting to 5.

The precision depends on the number of bits and the length of the pseudo-hash.

Using the defaults of 62 bits and a string length of 5, the maximum number that can be encrypted is 916,132,831.

With 32 bits (lower case only) the maximum for 5 characters is 60,466,175.

With 32 bits and a 6 character string, the maximum is 2,176,782,335.

Please let me know if you find this useful. Any issues or comments would be appreciated at Github.