Answer 1

https://m.youtube.com/watch?v=U9tP77AEF8w

https://stackoverflow.com/questions/21290382/creating-a-simple-encryption-program

https://null-byte.wonderhowto.com/how-to/create-encryption-program-with-JUMP_LINK__&&__python__&&__JUMP_LINK-0164249/

https://www.google.co.za/amp/www.instructables.com/id/Create-Simple-Message-EncrypterDecrypter-Using-No/%3famp_page=true

http://www.securitytube.net/video/3830

Answer 2

you can use encryption algorithm libraries

Answer 3

This is very complicated. Try to use something which already exists.