In this example we will learn how to verify the digital signature of the previously signed data. To sign the data you can see the previous example on this post How to create a digital signature and sign data?.

Here the code snippet:

package org.kodejava.security;

import java.nio.file.Files;
import java.nio.file.Paths;
import java.security.KeyFactory;
import java.security.PublicKey;
import java.security.Signature;
import java.security.spec.X509EncodedKeySpec;

public class VerifyDigitalSignature {
    public static void main(String[] args) {
        try {
            byte[] publicKeyEncoded = Files.readAllBytes(Paths.get("publickey"));
            byte[] digitalSignature = Files.readAllBytes(Paths.get("signature"));

            X509EncodedKeySpec publicKeySpec = new X509EncodedKeySpec(publicKeyEncoded);
            KeyFactory keyFactory = KeyFactory.getInstance("DSA", "SUN");

            PublicKey publicKey = keyFactory.generatePublic(publicKeySpec);
            Signature signature = Signature.getInstance("SHA1withDSA", "SUN");
            signature.initVerify(publicKey);

            byte[] bytes = Files.readAllBytes(Paths.get("README.md"));
            signature.update(bytes);

            boolean verified = signature.verify(digitalSignature);
            if (verified) {
                System.out.println("Data verified.");
            } else {
                System.out.println("Cannot verify data.");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

• Author
• Recent Posts

Wayan

Founder at Kode Java

A programmer, runner and recreational diver, lives on the island of Bali, Indonesia. Programming in Java, Spring Framework, Hibernate / JPA, MySQL. To support me working on this project, buy me a cup of coffee, every little bit helps. Thank you.

Latest posts by Wayan (see all)

• How do I get number of each day for a certain month in Java? - September 8, 2024
• How do I get operating system process information using ProcessHandle? - July 22, 2024
• How do I sum a BigDecimal property of a list of objects using Java Stream API? - July 22, 2024