HackerRank: Java SHA-256

Cryptographic hash functions are mathematical operations run on digital data; by comparing the computed hash (i.e., the output produced by executing a hashing algorithm) to a known and expected hash value, a person can determine the data's integrity. For example, computing the hash of a downloaded file and comparing the result to a previously published hash result can show whether the download has been modified or tampered with. In addition, cryptographic hash functions are extremely collision-resistant; in other words, it should be extremely difficult to produce the same hash output from two different input values using a cryptographic hash function.

Secure Hash Algorithm 2 (SHA-2) is a set of cryptographic hash functions designed by the National Security Agency (NSA). It consists of six identical hashing algorithms (i.e., SHA-256, SHA-512, SHA-224, SHA-384, SHA-512/224, SHA-512/256) with a variable digest size. SHA-256 is a 256-bit (32 byte) hashing algorithm which can calculate a hash code for an input of up to 264-1 bits. It undergoes 64 rounds of hashing and calculates a hash code that is a 64-digit hexadecimal number.

Given a string, s, print its SHA-256 hash value.

Sample Input 0

HelloWorld

Sample Output 0

872e4e50ce9990d8b041330c47c9ddd11bec6b503ae9386a99da8584e9bb12c4

Sample Input 1

Javarmi123

Sample Output 1

f1d5f8d75bb55c777207c251d07d9091dc10fe7d6682db869106aacb4b7df678

Java Code:

import java.nio.charset.StandardCharsets;

import java.security.MessageDigest;

import java.security.NoSuchAlgorithmException;

import java.util.Scanner;

public class javaSHA256

{

    public static void main(String[] args)

    {

        Scanner sc = new Scanner(System.in);

        String originalString = sc.nextLine();

       

        try {

            MessageDigest digest = MessageDigest.getInstance("SHA-256");

            byte[] encodedhash = digest.digest(

                originalString.getBytes(StandardCharsets.UTF_8));

            System.out.println(bytesToHex(encodedhash));

        }

        catch (NoSuchAlgorithmException e) {

            System.out.println(e);

        }

        sc.close();

    }

    private static String bytesToHex(byte[] hash) {

        StringBuilder hexString = new StringBuilder(2 * hash.length);

        for (int i = 0; i < hash.length; i++) {

            String hex = Integer.toHexString(0xff & hash[i]);

            if(hex.length() == 1) {

                hexString.append('0');

            }

            hexString.append(hex);

        }

        return hexString.toString();

    }

}

Note: Comment if you want Explanation.