How do I view the signature (MD5 or SHA1) of the certificate used to sign a given Android APK?
Your APK is a ZIP file, so extract the signature file located inside META-INF/{filename}.RSA. For some reason the {filename} can vary, but in my example it is CERT.RSA. View the signature information using the keytool:
keytool -printcert –file CERT.RSA
