This app signs update.zip files, APK, or JAR files using your own private keys or one of the four built-in certificates (media, platform, shared, testkey). All output is automatically zip-aligned. ZipSigner can work with existing keystores, or you can create keystores, keys, and self-signed certificates with this app. JKS and BKS keystores are supported. A certificate's MD5 and SHA1 fingerprints, as well as the SHA1 key hash, can be copied from the key properties screen. Think of this app as a combination of jarsigner, signapk, keytool, and zipalign.
The built-in keys and auto-selection modes will appeal to themers and modders. The ability to sign with private keys will appeal to developers.
This app does not require root privileges.
See the website for full documentation.