generate method
Implementation
String generate(int len, [dynamic add]) {
var temp = [];
while (temp.length < len) {
this.V = this._hmac().update(this.V).digest().bytes;
temp.insertAll(temp.length, this.V);
}
var res = temp.sublist(0, len);
this._update(add);
this._reseed++;
return toHex(res);
}