JAR files are the Java platform equivalent of ZIP files, allowing multiple Java class files to be packaged into one file with a .jar extension. This JAR file can then be digitally signed, proving the origin and the integrity of the class file code inside. A recipient of the JAR file can decide whether or not to trust the code based on the signature of the sender and can be confident that the contents have not been tampered with before receipt. The JDK comes with a jarsigner tool that provides this function.

In deployment, access to machine resources can be based on the signer's identity by putting access control statements in the policy file.