Trail Lessons Security Features Overview briefly describes the security features available in JDK 1.2. Quick Tour of Controlling Applets provides an overview of some of the new features. This lesson shows how resource accesses, such as reading or writing a file, are not permitted for applets unless explicitly allowed by a permission in a policy file. Quick Tour of Controlling Applications builds on the previous lesson, showing that when applications are run under a security manager, resource accesses may be controlled in exactly the same way as for applets. API and Tools Use for Secure Code and File Exchanges describes digital signatures, certificates, and keystores and discusses why they are needed.
Permissions illustrates the use of all the security-related tools.
It shows the steps that a developer would take to sign and to distribute code for others to run. Exchanging Files shows use of the tools by one person to sign an important document, such as a contract, and to export the public key certificate for the public key corresponding to the private key used to sign the contract. Then the lesson shows how another person, who receives the contract, the signature, and the public key certificate, can import the certificate and verify the signature. Generating and Verifying Signatures walks you step by step through an example of writing a Java program using the JDK Security API to generate keys, to generate a digital signature for data using the private key, and to export the public key and the signature to files. Then the example shows writing a second program, which may be expected to run on a different person's computer, that imports the public key and verifies the authenticity of the signature.