Java में Hashing (MD5, SHA)

import java.security.MessageDigest;
public class Main {
	public static void main(String[] args) throws Exception {
		MessageDigest digest = MessageDigest.getInstance("SHA-256");
		byte[] hash = digest.digest("hello".getBytes());
		System.out.println("Fixed length: " + hash.length + " bytes"); // one-way, no reverse algorithm exists
	}
}

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import java.security.MessageDigest;
public class Main {
	public static void main(String[] args) throws Exception {
		MessageDigest digest = MessageDigest.getInstance("MD5"); // fast but has known collision attacks
		byte[] hash = digest.digest("data".getBytes());
		System.out.println(hash.length + " bytes -- never use for passwords");
	}
}

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import java.security.MessageDigest;
public class Main {
	public static void main(String[] args) throws Exception {
		MessageDigest digest = MessageDigest.getInstance("SHA-256"); // current standard for integrity checks
		byte[] hash = digest.digest("data".getBytes());
		StringBuilder hex = new StringBuilder();
		for (byte b : hash) hex.append(String.format("%02x", b));
		System.out.println(hex);
	}
}

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import java.security.*;
public class Main {
	public static void main(String[] args) throws Exception {
		SecureRandom random = new SecureRandom();
		byte[] salt = new byte[16];
		random.nextBytes(salt); // random per user, stored alongside the hash
		MessageDigest digest = MessageDigest.getInstance("SHA-256");
		digest.update(salt);
		byte[] hash = digest.digest("password123".getBytes());
		System.out.println("Salted hash length: " + hash.length);
	}
}

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import java.security.*;
import java.util.Arrays;
public class Main {
	public static void main(String[] args) throws Exception {
		byte[] salt = "fixedSaltForDemo".getBytes();
		MessageDigest digest = MessageDigest.getInstance("SHA-256");
		digest.update(salt);
		byte[] storedHash = digest.digest("password123".getBytes());
		digest.reset();
		digest.update(salt);
		byte[] submittedHash = digest.digest("password123".getBytes()); // recomputed with the same salt
		System.out.println(Arrays.equals(storedHash, submittedHash));
	}
}

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