Convert crypto.randomBytes() to 8 digit random integer

Question

In my node.js server side code, while trying to create 8 digit random number, the result is not as expected.

I tried below code,

const crypto = require('crypto');
var token = crypto.randomBytes(8);

console.log(token);

Still it returns bufferred bytearray which is <Buffer 1d c3 02 b1 d1 0b e9 dc>. Tried a lot of methods to convert that byte array to 8 digit number like 98988348(Not a hexadecimal one).

But still not able to get the 8 Digit random number.

Note:Don't want to use Math.random() here.

Answer 1

crypto.randomInt (Node.js v14.10+/v12.19+)

As of Node.js v14.10 (and v12.19), the crypto module exports a randomInt([min], max, [callback]) function which returns a random integer n such that min <= n < max. This function inherits all of the security benefits that the crypto module as a whole provides.

So to get a random 8 digit integer, you'd be looking to invoke the randomInt function with a min value of 10000000 and a max of 100000000:

const { randomInt } = require('crypto');

const n = randomInt(10000000, 100000000);

crypto.randomBytes

An alternative that doesn't have strict Node.js version requirements would be to convert your buffer to a hex string, and then use the parseInt function specifying the base parameter as 16 (for hex).

You can then divide that parsed integer by the largest possible value (0xffffffffffffffff) to get a cryptographically-secure number between 0 and 1.

Now you just need to multiply this by (max - min) (90000000 in your case) and then add the min (10000000).

const { randomBytes } = require('crypto');

const token = crypto.randomBytes(8);
const hex = token.toString('hex');

const min = 10000000;
const max = 100000000;

let n = parseInt(hex, 16); // 0   <= n < 2^64
n /= 0xffffffffffffffff;   // 0   <= n < 1
n *= max - min;            // 0   <= n < max - min
n += min;                  // min <= n < max