I am using midp 2.0. Here, I am using FileConnection for read and write files on mobile memory. I am able to read and write files on mobiles successfully. But while I am try
If you go to 3rd party trusted certificate means its minimum cost is RS.10000 per year. For deploying your application in client (final stage). It will worth.
But for testing, validating input, developing stage the cost is high. So check if your mobile has support for self signed certificate. If it supports self signed certificate, then process with self signed certificate.
But keep in mind self signed certificate is only for testing / development purpose. For delivering the project to client you should go to trusted party certificates.