The Android system requires all the installed applications to be digitally signed with a certificate whose private key is held by the application's developer. The Android system uses the certificate as a means of identifying the author of an application and establishing a relationship of trust between applications. The certificate is not used to control which applications the user can install. The certificate does not need to be signed by a certificate authority; it can be self-signed. Certificates can be signed on either Mac or Windows systems.
On the Mac, go to Applications | Utilities | Terminal. On Windows, go to Start Menu | All Programs | Accessories | Command Prompt. Using the
keytoolcommand, add in the following lines and press Enter:keytool -genkey -v -keystore my-release-key.keystore -alias aliasname -keyalg RSA -validity 999999