best way to do in android client and secure web service

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http://stackoverflow.com – so i have a problem with unauthorized usage of my c# web service so here it goes Problem: I have an android client application and it takes data from c# web service.Now my problem is i don't want other people/application to consume the services.So i want to restrict the usage to my application only. Solution(that i have currently): 1.Create a username/password and store(encrypted form) it in android client application. 2.My android application will send the decrypted username/password to web service. 3.since the username/password is decrypted while journey to web service it is not safe since (HowTos)