title: Changing android app certificate
body: <p>I am getting this message: The apk must be signed with the same certificates as the previous version. 
  I read this: <a href="https://stackoverflow.com/questions/4843212/the-apk-must-be-signed-with-the-same-certificates-as-the-previous-version">enter link description here</a></p>
  
  <p>But here is my dilemma.
  This app was created by another developer. So i have all the files from him. Now i updated the app i am trying to upload it to market its giving me this error. Is there anyway to get this from project files i have from previous version of the app? By what name will this file be saved on the previous version? How can i reuse it.</p>