Java Signature initSign() method with Examples

The initSign() method initialize this object for signing. If this method is called again with a different argument, it negates the effect of this call.

Let us now see an example −

Example

import java.security.KeyPair; import java.security.KeyPairGenerator; import java.security.PrivateKey; import java.security.Signature; import java.util.Scanner; public class Main {    public static void main(String args[]) throws Exception {       //Creating KeyPair generator object       KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("DSA");       //Initializing the key pair generator       keyPairGen.initialize(2048);       //Generate the pair of keys       KeyPair pair = keyPairGen.generateKeyPair();       //Getting the privatekey from the key pair       PrivateKey privKey = pair.getPrivate();       //Creating a Signature object       Signature sign = Signature.getInstance("SHA256withDSA");       //Initializing the signature       sign.initSign(privKey);       byte[] bytes = "Hello how are you".getBytes();       //Adding data to the signature       sign.update(bytes);       //Calculating the signature       byte[] signature = sign.sign();       //Initializing the signature       sign.initVerify(pair.getPublic());       sign.update(bytes);       //Verifying the signature       boolean bool = sign.verify(signature);       if(bool) {          System.out.println("Signature verified");       } else {          System.out.println("Signature failed");       }    } }

Output

Signature verified