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SecureRandom setSeed() method in Java with Examples

  • Last Updated : 04 Dec, 2018
setSeed( byte[] seed )

The setSeed() method of java.security.SecureRandom class is used to reseeds this random object. The given seed supplements, rather than replaces, the existing seed. Thus, repeated calls are guaranteed never to reduce randomness.

Syntax:

public void setSeed(byte[] seed)

Parameters: This method takes the seed as a parameter.

Note: Every time Secure Random class will generate random output

Below are the examples to illustrate the setSeed() method:



Example 1:




// Java program to demonstrate
// setSeed() method
  
import java.security.*;
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv)
    {
        try {
            // creating the object of SecureRandom
            SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
  
            // Declaring the string variable
            String str = "Tajmahal";
  
            // Declaring the byte Array b
            byte[] b = str.getBytes();
  
            // Reseeding the random object
            sr.setSeed(b);
  
            // getting the seeds
            byte[] seeds = sr.getSeed(10);
  
            // printing the seed serialwise
            for (int i = 0; i < seeds.length; i++)
                System.out.println("Seed[" + i + "] : " + seeds[i]);
        }
  
        catch (NoSuchAlgorithmException e) {
  
            System.out.println("Exception thrown : " + e);
        }
  
        catch (ProviderException e) {
  
            System.out.println("Exception thrown : " + e);
        }
    }
}

Output:

Seed[0]:69
Seed[0] : 23
Seed[1] : -99
Seed[2] : -51
Seed[3] : 107
Seed[4] : 41
Seed[5] : -96
Seed[6] : -93
Seed[7] : -86
Seed[8] : 127
Seed[9] : 47

Example 2:




// Java program to demonstrate
// setSeed() method
  
import java.security.*;
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv)
    {
        try {
            // creating the object of SecureRandom
            SecureRandom sr = new SecureRandom(new byte[] { 1, 2, 3, 4 });
  
            // Declaring the string variable
            String str = "Tajmahal";
  
            // Declaring the byte Array b
            byte[] b = str.getBytes();
  
            // Reseeding the random object
            sr.setSeed(b);
  
            // getting the seeds
            byte[] seeds = sr.getSeed(10);
  
            // printing the seed serialwise
            for (int i = 0; i < seeds.length; i++)
                System.out.println("Seed[" + i + "]:" + seeds[i]);
        }
  
        catch (ProviderException e) {
  
            System.out.println("Exception thrown : " + e);
        }
    }
}

Output:

Seed[0]:92
Seed[1]:127
Seed[2]:28
Seed[3]:-127
Seed[4]:-100
Seed[5]:-110
Seed[6]:86
Seed[7]:-55
Seed[8]:48
Seed[9]:-78


setSeed(long seed)


The setSeed(long seed) method of java.security.SecureRandom class is used to reseeds this random object, using the eight bytes contained in the given long seed. The given seed supplements, rather than replaces, the existing seed. Thus, repeated calls are guaranteed never to reduce randomness.

Syntax:



public void setSeed( long seed )

Parameters: This method takes the seed as a parameter

Note: Every time Secure Random class will generate random output

Below are the examples to illustrate the setSeed() method:

Example 1:




// Java program to demonstrate
// setSeed() method
  
import java.security.*;
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv) throws Exception
    {
        try {
            // creating the object of SecureRandom
            SecureRandom sr = SecureRandom.getInstance("SHA1PRNG", "SUN");
  
            // Reseeding the random object
            sr.setSeed(101L);
  
            // getting the seeds
            byte[] seeds = sr.getSeed(10);
  
            // printing the seed serialwise
            for (int i = 0; i < seeds.length; i++)
                System.out.println("Seed[" + i + "] : " + seeds[i]);
        }
  
        catch (NoSuchAlgorithmException e) {
  
            System.out.println("Exception thrown : " + e);
        }
  
        catch (ProviderException e) {
  
            System.out.println("Exception thrown : " + e);
        }
    }
}

Output:

Seed[0] : -36
Seed[1] : -65
Seed[2] : -94
Seed[3] : 16
Seed[4] : -104

Example 2:




// Java program to demonstrate
// setSeed() method
  
import java.security.*;
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv)
    {
        try {
            // creating the object of SecureRandom
            SecureRandom sr = new SecureRandom(new byte[] { 1, 2, 3, 4 });
  
            // Reseeding the random object
            sr.setSeed(101L);
  
            // getting the seeds
            byte[] seeds = sr.getSeed(10);
  
            // printing the seed serialwise
            for (int i = 0; i < seeds.length; i++)
                System.out.println("Seed[" + i + "]:" + seeds[i]);
        }
  
        catch (ProviderException e) {
  
            System.out.println("Exception thrown : " + e);
        }
    }
}

Output:

Seed[0]:-29
Seed[1]:-93
Seed[2]:6
Seed[3]:66
Seed[4]:126
Seed[5]:93
Seed[6]:-58
Seed[7]:-91
Seed[8]:-62
Seed[9]:-58

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