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Trail: Security Features in Java SE
Lesson: Generating and Verifying Signatures
Section: Generating a Digital Signature
Generating and Verifying Signatures
Generating a Digital Signature
Prepare Initial Program Structure
Generate Public and Private Keys
Sign the Data
Save the Signature and the Public Key in Files
Compile and Run the Program
Verifying a Digital Signature
Prepare Initial Program Structure
Input and Convert the Encoded Public Key Bytes
Input the Signature Bytes
Verify the Signature
Compile and Run the Program
Weaknesses and Alternatives
Home Page > Security Features in Java SE > Generating and Verifying Signatures
Prepare Initial Program Structure

> Here's the basic structure of the `GenSig` program. Place it in a file called `GenSig.java`.

> >     import java.io.*;
> >     import java.security.*;

> >     class GenSig {

> >         public static void main(String[] args) {

> >             /* Generate a DSA signature */

> >             if (args.length != 1) {
> >                 System.out.println("Usage: GenSig nameOfFileToSign");
> >                 }
> >             else try {

> >             // the rest of the code goes here

> >             } catch (Exception e) {
> >                 System.err.println("Caught exception " + e.toString());
> >             }
> >         }

> >     }

> Notes:
> - The methods for signing data are in the `java.security` package, so the program imports everything from that package. The program also imports the `java.io` package, which contains the methods needed to input the file data to be signed.

> - A single argument is expected, specifying the data file to be signed.

> - The code written in subsequent steps will go between the `try` and the `catch` blocks.

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