deterministic RSA keys

make-key.js

const forge = require('node-forge');
const rsa = forge.pki.rsa;
function fix (str) {
  return str.replace(/\r/g, '') + '\n'
}
exports.makeKey = function makeKey(id){
    const prng = {
        getBytesSync(_length){
            const _id = '_' + id;
            return {
                charCodeAt(i){
                    return _id.charCodeAt(i % id.length);
                }
            };
        }
    };
    return new Promise(res => {
        // generate an RSA key pair in steps that attempt to run for a specified period
        // of time on the main JS thread
        var state = rsa.createKeyPairGenerationState(2048, 0x10001, {prng});
        var step = function() {
        // run for 100 ms
        if(!rsa.stepKeyPairGenerationState(state, 100)) {
            setTimeout(step, 1);
        }
        else {
            // done, turn off progress indicator, use state.keys
            // res(state.keys);
            res({
                publicKeyArmored: fix(forge.pki.publicKeyToRSAPublicKeyPem(state.keys.publicKey, 72)),
                privateKeyArmored: fix(forge.pki.privateKeyToPem(state.keys.privateKey, 72))
              });
        }
        };
        // turn on progress indicator, schedule generation to run
        setTimeout(step, 1);
    });
}