apksig is a project which aims to simplify APK signing and checking whether APK's signatures should verify on Android. apksig supports JAR signing (used by Android since day one) and APK Signature Scheme v2 (supported since Android Nougat, API Level 24).
The key feature of apksig is that it knows about differences in APK signature verification logic between different versions of the Android platform. apksig can thus check whether a signed APK is expected to verify on all Android platform versions supported by the APK. When signing an APK, apksig will choose the most appropriate cryptographic algorithms based on the Android platform versions supported by the APK being signed.
The project consists of two subprojects:
apksig library offers three primitives:
ApkSignerwhich signs the provided APK so that it verifies on all Android platform versions supported by the APK. The range of platform versions can be customized if necessary.
ApkVerifierwhich checks whether the provided APK is expected to verify on all Android platform versions supported by the APK. The range of platform versions can be customized if necessary.
(Default)ApkSignerEnginewhich abstracts away signing an APK from parsing and building an APK file. This is useful in optimized APK building pipelines, such as in Android Plugin for Gradle, which need to perform signing while building an APK, instead of after. For simpler use cases where the APK to be signed is available upfront, the
ApkSignerabove is easier to use.
NOTE: Some public classes of the library are in packages having the word “internal” in their name. These are not public API of the library. Do not use *.internal.* classes directly.
apksigner command-line tool offers two operations:
apksigner signfor usage information.
apksigner verifyfor usage information.
The tool determines the range of Android platform versions (API Levels) supported by the APK by inspecting the APK's AndroidManifest.xml. This behavior can be overridden by specifying the range of platform versions on the command-line.