KeyPairGenerator initialize() method in Java with Examples

initialize(int keysize)

The initialize() method of java.security.KeyPairGenerator is ysed 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:

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// Java program to demonstrate
// genKeyPair() method
  
import java.security.*;
import java.util.*;
  
public class GFG {
    public static void main(String[] argv) throws Exception
    {
        try {
  
            // creating the object of KeyPairGenerator
            KeyPairGenerator kpg
                = KeyPairGenerator
                      .getInstance("RSA");
  
            // initializing with 1024
            kpg.initialize(1024);
  
            // getting key pairs
            // using genKeyPair() method
            KeyPair kp = kpg.genKeyPair();
  
            // pritning the Keypair
            System.out.println("Keypair : " + kp);
        }
  
        catch (NoSuchAlgorithmException e) {
  
            System.out.println("Exception thrown : " + e);
        }
    }
}

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Output:


Keypair : java.security.KeyPair@12a3a380





Example 2: For InvalidParameterException











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// Java program to demonstrate 


// genKeyPair() method 


  


import java.security.*; 


import java.util.*; 


  


public class GFG { 


    public static void main(String[] argv) throws Exception 


    { 


        try { 


  


            // creating the object of KeyPairGenerator 


            KeyPairGenerator kpg 


                = KeyPairGenerator 


                      .getInstance("RSA"); 


  


            // initializing with 1024 


            kpg.initialize(-24); 


  


            // getting key pairs 


            // using genKeyPair() method 


            KeyPair kp = kpg.genKeyPair(); 


  


            // pritning the Keypair 


            System.out.println("Keypair : " + kp); 


        } 


  


        catch (NoSuchAlgorithmException e) { 


  


            System.out.println("Exception thrown : " + e); 


        } 


        catch (InvalidParameterException e) { 


  


            System.out.println("Exception thrown : " + e); 


        } 


    } 


} 



















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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 a 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:











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// Java program to demonstrate 


// genKeyPair() method 


  


import java.security.*; 


import java.util.*; 


  


public class GFG { 


    public static void main(String[] argv) 


        throws Exception 


    { 


        try { 


  


            // creating the object of KeyPairGenerator 


            KeyPairGenerator kpg 


                = KeyPairGenerator 


                      .getInstance("RSA"); 


  


            // creating the object of SecureRandom 


            SecureRandom se 


                = SecureRandom.getInstance("SHA1PRNG"); 


  


            // initializing with 1024 


            kpg.initialize(1024, se); 


  


            // getting key pairs 


            // using genKeyPair() method 


            KeyPair kp = kpg.genKeyPair(); 


  


            // pritning the Keypair 


            System.out.println("Keypair : " + kp); 


        } 


  


        catch (NoSuchAlgorithmException e) { 


  


            System.out.println("Exception thrown : " + e); 


        } 


        catch (InvalidParameterException e) { 


  


            System.out.println("Exception thrown : " + e); 


        } 


    } 


} 



















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Output:


Keypair : java.security.KeyPair@4e25154f




Example 2: For InvalidParameterException











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// Java program to demonstrate 


// genKeyPair() method 


  


import java.security.*; 


import java.util.*; 


  


public class GFG { 


    public static void main(String[] argv) 


        throws Exception 


    { 


        try { 


  


            // creating the object of KeyPairGenerator 


            KeyPairGenerator kpg 


                = KeyPairGenerator 


                      .getInstance("RSA"); 


  


            // creating the object of SecureRandom 


            SecureRandom se 


                = SecureRandom.getInstance("SHA1PRNG"); 


  


            // initializing with -24 


            kpg.initialize(-24, se); 


  


            // getting key pairs 


            // using genKeyPair() method 


            KeyPair kp = kpg.genKeyPair(); 


  


            // pritning the Keypair 


            System.out.println("Keypair : " + kp); 


        } 


  


        catch (NoSuchAlgorithmException e) { 


  


            System.out.println("Exception thrown : " + e); 


        } 


        catch (InvalidParameterException e) { 


  


            System.out.println("Exception thrown : " + e); 


        } 


    } 


} 



















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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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