The Java TM Tutorial

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Trail: Security in JDK 1.2
Lesson: Generating and Verifying Signatures

## Generating a Digital Signature

> The `GenSig` program you are about to create will use the JDK Security API to generate keys and a digital signature for data using the private key and to export the public key and the signature to files. The application gets the data file name from the command line.

> The following steps create the `GenSig` sample program.

> > 1. Prepare Initial Program Structure

> >    Create a text file named `GenSig.java`. Type in the initial program structure (import statements, class name, `main` method, and so on).

> > 2. Generate Public and Private Keys

> >    Generate a key pair (public key and private key). The private key is needed for signing the data. The public key will be used by the `VerSig` program for verifying the signature.

> > 3. Sign the Data

> >    Get a `Signature` object and initialize it for signing. Supply it with the data to be signed, and generate the signature.

> > 4. Save the Signature and the Public Key in Files

> >    Save the signature bytes in one file and the public key bytes in another.

> > 5. Compile and Run the Program

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