KeyPairGenerator initialize() method in Java with Examples
Last Updated :
27 Jan, 2023
initialize(int keysize)
The initialize() method of java.security.KeyPairGenerator is used to initialize KeyPairGenerator object for further use.
Syntax:
public void initialize(int keysize)
Parameters: This method seeks keysize of int type as a parameter.
Return Value: This method has nothing to return.
Exception: This method throws InvalidParameterException if the greater or lesser value than the specified criteria is passed.
Note: The following program will not run on the online IDE.
Below are the examples to illustrate the initialize(int keysize) method:
Example 1:
Java
import java.security.*;
import java.util.*;
public class GFG {
public static void main(String[] argv) throws Exception
{
try {
KeyPairGenerator kpg
= KeyPairGenerator
.getInstance( "RSA" );
kpg.initialize( 1024 );
KeyPair kp = kpg.genKeyPair();
System.out.println( "Keypair : " + kp);
}
catch (NoSuchAlgorithmException e) {
System.out.println( "Exception thrown : " + e);
}
}
}
|
Output:
Keypair : java.security.KeyPair@12a3a380
Example 2: For InvalidParameterException
Java
import java.security.*;
import java.util.*;
public class GFG {
public static void main(String[] argv) throws Exception
{
try {
KeyPairGenerator kpg
= KeyPairGenerator
.getInstance( "RSA" );
kpg.initialize(- 24 );
KeyPair kp = kpg.genKeyPair();
System.out.println( "Keypair : " + kp);
}
catch (NoSuchAlgorithmException e) {
System.out.println( "Exception thrown : " + e);
}
catch (InvalidParameterException e) {
System.out.println( "Exception thrown : " + e);
}
}
}
|
Output:
Exception thrown :
java.security.InvalidParameterException:
RSA keys must be at least 512 bits long
initialize(int keysize, SecureRandom random)
The initialize() method of java.security.KeyPairGenerator initializes KeyPairGenerator for particular size with SecureRandom object to use further.
Syntax:
public void initialize(int keysize,
SecureRandom random)
Parameters: This method takes the following arguments as parameters:
- size: which is the keysize
- random: which is the object of SecureRandom type
Return Value: This method provides the object of KeyPairGenerator.
Exception: This method throws InvalidParameterException if the greater or lesser value than the specified criteria is passed.
Below are the examples to illustrate the initialize() method:
Example 1:
Java
import java.security.*;
import java.util.*;
public class GFG {
public static void main(String[] argv)
throws Exception
{
try {
KeyPairGenerator kpg
= KeyPairGenerator
.getInstance( "RSA" );
SecureRandom se
= SecureRandom.getInstance( "SHA1PRNG" );
kpg.initialize( 1024 , se);
KeyPair kp = kpg.genKeyPair();
System.out.println( "Keypair : " + kp);
}
catch (NoSuchAlgorithmException e) {
System.out.println( "Exception thrown : " + e);
}
catch (InvalidParameterException e) {
System.out.println( "Exception thrown : " + e);
}
}
}
|
Output:
Keypair : java.security.KeyPair@4e25154f
Example 2: For InvalidParameterException
Java
import java.security.*;
import java.util.*;
public class GFG {
public static void main(String[] argv)
throws Exception
{
try {
KeyPairGenerator kpg
= KeyPairGenerator
.getInstance( "RSA" );
SecureRandom se
= SecureRandom.getInstance( "SHA1PRNG" );
kpg.initialize(- 24 , se);
KeyPair kp = kpg.genKeyPair();
System.out.println( "Keypair : " + kp);
}
catch (NoSuchAlgorithmException e) {
System.out.println( "Exception thrown : " + e);
}
catch (InvalidParameterException e) {
System.out.println( "Exception thrown : " + e);
}
}
}
|
Output:
Exception thrown :
java.security.InvalidParameterException:
RSA keys must be at least 512 bits long
Reference: https://docs.oracle.com/javase/9/docs/api/java/security/KeyPairGenerator.html#initialize-int-java.security.SecureRandom-
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