initSign(PrivateKey privateKey)
The initSign() method of java.security.Provider class is used to initialize this object for signing. If this method is called again with a different argument, it negates the effect of this call.
Syntax:
public final void
initSign(PrivateKey privateKey)
throws InvalidKeyException
Parameters: This method takes the private key of the identity as parameter whose signature is going to be generated
Exception: This method throws InvalidKeyException if the key is invalid.
Below are the examples to illustrate the initSign() method:
Note: The following program will not run in online IDE
Example 1:
// Java program to demonstrate
// initSign() method
import java.security.*;
import java.util.*;
import sun.misc.BASE64Encoder;
public class GFG1 {
public static void main(String[] argv) throws Exception
{
try {
// calling getKeyPair() method and assigning in keypair
KeyPair keyPair = getKeyPair();
// creating byte array object
byte[] outbuff = new byte[1000];
// data to be updated
byte[] data = "test".getBytes("UTF8");
// creating the object of Signature
Signature sr = Signature.getInstance("SHA1WithRSA");
// initializing the signature object with key pair
// for signing
// Using method initSign
sr.initSign(keyPair.getPrivate());
// updating the data
sr.update(data);
// getting the signature byte
// of an signing operation
// by using method sign()
byte[] bytes = sr.sign();
// printing the number of byte
System.out.println("Signature:" + Arrays.toString(bytes));
}
catch (NoSuchAlgorithmException e) {
System.out.println("Exception thrown : " + e);
}
catch (SignatureException e) {
System.out.println("Exception thrown : " + e);
}
}
// defining getKeyPair method
private static KeyPair getKeyPair() throws NoSuchAlgorithmException
{
// creating the object of KeyPairGenerator
KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
// initializing with 1024
kpg.initialize(1024);
// returning the key pairs
return kpg.genKeyPair();
}
}
Output:
Signature:[-109, -21, 90, -114, -22, .... .... ...., 92, 1]
Example 2: To show InvalidKeyException
// Java program to demonstrate
// initSign() method
import java.security.*;
import java.util.*;
public class GFG1 {
public static void main(String[] argv) throws Exception
{
try {
// data to be updated
byte[] data = "test".getBytes("UTF8");
// creating the object of Signature
Signature sr = Signature.getInstance("SHA1WithRSA");
// initializing the signature object with key pair
// for signing
// Using method initSign
System.out.println("Trying to put null as private key ");
sr.initSign(null);
// updating the data
sr.update(data);
// getting the signature byte
// of an signing operation
// by using method sign()
byte[] bytes = sr.sign();
// printing the number of byte
System.out.println("Signature:" + Arrays.toString(bytes));
}
catch (NoSuchAlgorithmException e) {
System.out.println("Exception thrown : " + e);
}
catch (SignatureException e) {
System.out.println("Exception thrown : " + e);
}
catch (InvalidKeyException e) {
System.out.println("Exception thrown : " + e);
}
}
}
Output:
Trying to put null as private key Exception thrown : java.security.InvalidKeyException: Key must not be null
initSign(PrivateKey privateKey, SecureRandom random)
The initSign() method of java.security.Provider class is used to initialize this object for signing. If this method is called again with a different argument, it negates the effect of this call.
Syntax:
public final void
initSign(PrivateKey privateKey, SecureRandom random)
throws InvalidKeyException
Parameters: This method takes following parameters:
- privateKey- the private key of the identity whose signature is going to be generated.
- random- the source of randomness for this signature.
Exception: This method throws InvalidKeyException if the key is invalid.
Below are the examples to illustrate the sign() method:
Note: The following program will not run in online IDE
Example 1:
// Java program to demonstrate
// initsign() method
import java.security.*;
import java.util.*;
import sun.misc.BASE64Encoder;
public class GFG1 {
public static void main(String[] argv) throws Exception
{
try {
// calling getKeyPair() method and assigning in keypair
KeyPair keyPair = getKeyPair();
// creating byte array object
byte[] outbuff = new byte[1000];
// data to be updated
byte[] data = "test".getBytes("UTF8");
// creating the object of Signature
Signature sr = Signature.getInstance("SHA1WithRSA");
// creating the object of SecureRandom
SecureRandom sb = SecureRandom.getInstance("SHA1PRNG");
// initializing the signature object with key pair
// for signing
sr.initSign(keyPair.getPrivate(), sb);
// updating the data
sr.update(data);
// getting the signature byte
// of an signing operation
// by using method sign()
byte[] bytes = sr.sign();
// printing the number of byte
System.out.println("Signature:" + Arrays.toString(bytes));
}
catch (NoSuchAlgorithmException e) {
System.out.println("Exception thrown : " + e);
}
catch (SignatureException e) {
System.out.println("Exception thrown : " + e);
}
}
// defining getKeyPair method
private static KeyPair getKeyPair() throws NoSuchAlgorithmException
{
// creating the object of KeyPairGenerator
KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
// initializing with 1024
kpg.initialize(1024);
// returning the key pairs
return kpg.genKeyPair();
}
}
Output:
Signature:[-121, -82, .... .... ....104, 114, -67]
Example 2: To show InvalidKeyException
// Java program to demonstrate
// initSign() method
import java.security.*;
import java.util.*;
public class GFG1 {
public static void main(String[] argv) throws Exception
{
try {
// creating byte array object
byte[] outbuff = new byte[1000];
// data to be updated
byte[] data = "test".getBytes("UTF8");
// creating the object of Signature
Signature sr = Signature.getInstance("SHA1WithRSA");
// creating the object of SecureRandom
SecureRandom sb = SecureRandom.getInstance("SHA1PRNG");
// initializing the signature object with null key pair
// for signing using initSign() method
System.out.println("Trying to put the null as key");
sr.initSign(null, sb);
// updating the data
sr.update(data);
// getting the signature byte
// of an signing operation
// by using method sign()
byte[] bytes = sr.sign();
// printing the number of byte
System.out.println("Signature:" + Arrays.toString(bytes));
}
catch (NoSuchAlgorithmException e) {
System.out.println("Exception thrown : " + e);
}
catch (InvalidKeyException e) {
System.out.println("Exception thrown : " + e);
}
}
}
Output:
Trying to put the null as key Exception thrown : java.security.InvalidKeyException: Key must not be null