The Android system requires that all installed applications be digitally signed with a certificate whose private key is held by the application's developer.
Platforms: Smart Devices(Android)
When you build an apk (Android binary file) you use your own private key to sign your application. If you don't have a private key, you can use the Keytool utility (available with the JDK used to compile) to create one for you.
When you compile your application in release mode, the Android build tools use your private key along with the Jarsigner utility to sign your application's .apk file. Because the certificate and private key you use are your own, you will have to provide the password for the keystore and key alias.
This alias is needed to get the key of the certificate.
To get the Key Alias from the keystore you can execute this command line, the keytool utility can be found in the jdk\bin folder.
keytool -list -keystore your_keystore_name
A valid KeyStore key entry containing a private key and corresponding public key certificate chain.
Signing your applications
HowTo: Publishing an application in Google Play
Compile and sign your Android app by command line