I upload my first app into market, and now I want to upgrade a new version, but I got this exception when I upgrade my app. " The apk must be signed with the same certificates as the previous version." I lost my certificate keystore, what can I do in this situation? unpublish my app and rename the package? Can I upload other app using the other keystore?
Faced the same problem. I was trying to restore it via deleted files restoring tools, but it failed. So, there is no other way: you should issue another application.
Of course, any other your application you can upload with other certificate. It is used only for the security purposes: to ensure that upgrading person is the one who is the author.
Generally, the only advise that exists on keystores: always backup it!
来源：https://stackoverflow.com/questions/4470183/i-lost-my-keystore-i-cant-upgrade-my-app-in-the-market