message digest takes an arbitrary amount of input data creates a short, messageversion of the data, sometimes called a digital fingerprint, secure hash, or cryptographichash Write a simple JAVA program that creates message digest from a file.describe its methods under java. Security.Key

Sure, here is a simple Java program that creates a message digest from a file using the java.security.MessageDigest class.

import java.io.*;
import java.security.*;

public class FileDigest {
    public static void main(String[] args) throws Exception {
        // Check if file name is provided
        if (args.length != 1) {
            System.err.println("Usage: java FileDigest <file name>");
            return;
        }

        // Get file input stream for reading the file content
        FileInputStream fis = new FileInputStream(args[0]);

        // Create MessageDigest instance for MD5
        MessageDigest md = MessageDigest.getInstance("MD5");

        // Read file content in bytes
        byte[] byteArray = new byte[1024];
        int bytesCount = 0; 
        while ((bytesCount = fis.read(byteArray)) != -1) {
            md.update(byteArray, 0, bytesCount);
        };

        // Close the input stream
        fis.close();

        // Get the hash's bytes 
        byte[] bytes = md.digest();

        // Convert bytes to Hexadecimal
        StringBuilder sb = new StringBuilder();
        for(int i=0; i< bytes.length ;i++) {
            sb.append(Integer.toString((bytes[i] & 0xff) + 0x100, 16).substring(1));
        }

        // Get complete hashed password in hex format
        String fileDigest = sb.toString();

        // Print the digest
        System.out.println("Digest(in hex format):: " + fileDigest);
    }
}

This program uses the MessageDigest class from the java.security package. The MessageDigest class provides applications the functionality of a message digest algorithm, such as SHA-1 or SHA-256. Message digests are secure one-way hash functions that take arbitrary-sized data and output a fixed-length hash value.

Here are the methods used in the program:

• MessageDigest.getInstance(String algorithm): This method returns a MessageDigest object that implements the specified digest algorithm.

• update(byte[] input): This method updates the digest using the specified array of bytes.

• digest(): This method completes the hash computation by performing final operations such as padding. It returns the array of bytes for the resulting hash value.

• FileInputStream.read(byte[] b): This method reads up to b.length bytes of data from this input stream into an array of bytes. It returns the total number of bytes read into the buffer, or -1 if there is no more data because the end of the file has been reached.

• FileInputStream.close(): This method closes this file input stream and releases any system resources associated with the stream.