To use keytool to generate a keystore for code signing, take the following command, replace tj-vantoll with your name or company’s name, and replace NameOfYourApp with the name of your app.

keytool -genkey -v -keystore tj-vantoll.jks -keyalg RSA
-keysize 2048 -validity 10000 -alias NameOfYourApp

The keytool utility will ask you a number of questions, several of which are optional (name of organization, as well as the names of your city/state/country), but the most important ones are the passwords for both the keystore and the alias (more on that momentarily). Here’s what the keytool process looks like when I generate the keystore I used for Pokémon Types

https://www.nativescript.org/blog/steps-to-publish-your-nativescript-app-to-the-app-stores