How to access SecureRandom in jsbn typescript?

Question

I used to access the SecureRandom in jsbn.js this way

var jsbn = require('jsbn');
var SecureRandom = jsbn.SecureRandom;
var secureRandom = new SecureRandom();
secureRandom.nextBytes(x);

How do I access it in jsbn.ts? As there seem to be limited functions to import

 import jsbn, {BigInteger, RandomGenerator as SecureRandom} from "jsbn";

package.json

"dependencies": {
  "jsbn": "^1.1.0"
},
"devDependencies": {
  "@types/jsbn": "^1.2.29",
}

Thank you.

Answer 1

The @types/jsbn npm package only provides the declaration of an interface for the RandomGenerator and does not export the SecureRandom:

export interface RandomGenerator {
    nextBytes(bytes: number[]): void;
}

You should implement that interface and this nextBytes method with a prng as WebAPI Crypto getRandomValues()

For example:

class SecureRandomGenerator implements RandomGenerator {

    private static getRandomBytes(size: number): Uint8Array {
        // User agent WebAPI Crypto
        if (typeof window !== "undefined" && window.crypto && window.crypto.getRandomValues) {
            return window.crypto.getRandomValues(new Uint8Array(size));
        }

        throw new Error("Web API Crypto is not available");
    }

    public nextBytes(bytes: number[]): void {
        const generatedBytes = SecureRandomGenerator.getRandomBytes(bytes.length);
        for (let i = 0; i < bytes.length; i++) {
            bytes[i] = generatedBytes[i];
        }
    }

}