TheAlgorithms · karthikyandrapu · Aug 16, 2024 · Aug 16, 2024 · Aug 16, 2024
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+package com.thealgorithms.hashes;
+
+import java.security.*;
+import java.util.Base64;
+import java.util.Scanner;
+
+/**
+ * The DSS class demonstrates the use of the Digital Signature Algorithm (DSA) for signing and verifying messages.
+ * DSA is a Federal Information Processing Standard for digital signatures, based on the mathematical concept of modular exponentiation and discrete logarithms.
+ * 
+ * @see <a href="https://en.wikipedia.org/wiki/Digital_Signature_Algorithm">Digital Signature Algorithm on Wikipedia</a>
+ */
+public class DSS {
+
+    public static void main(String[] args) throws Exception {
+        // Generate a key pair (public and private keys) for DSA
+        KeyPair keyPair = generateKeyPair();
+
+        // Get message input from the user
+        Scanner scanner = new Scanner(System.in);
+        System.out.print("Enter the message to sign: ");
+        String message = scanner.nextLine();
+        scanner.close();
+
+        // Sign the message using the private key
+        byte[] signature = signMessage(message.getBytes(), keyPair.getPrivate());
+        System.out.println("Signature: " + Base64.getEncoder().encodeToString(signature));
+
+        // Verify the signature using the public key
+        boolean verified = verifySignature(message.getBytes(), signature, keyPair.getPublic());
+        System.out.println("Signature verified: " + verified);
+    }
+
+    /**
+     * Generates a DSA key pair (private and public keys).
+     *
+     * @return a KeyPair containing a DSA private key and public key
+     * @throws NoSuchAlgorithmException if the DSA algorithm is not available
+     */
+    public static KeyPair generateKeyPair() throws NoSuchAlgorithmException {
+        // Create a KeyPairGenerator for DSA
+        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("DSA");
+
+        // Initialize the KeyPairGenerator with a key size and a secure random number generator
+        SecureRandom secureRandom = new SecureRandom();
+        keyPairGenerator.initialize(1024, secureRandom);
+
+        // Generate and return the KeyPair
+        return keyPairGenerator.generateKeyPair();
+    }
+
+    /**
+     * Signs a message using a private key.
+     *
+     * @param message    the message to be signed
+     * @param privateKey the private key used to sign the message
+     * @return a byte array containing the digital signature
+     * @throws Exception if an error occurs during the signing process
+     */
+    public static byte[] signMessage(byte[] message, PrivateKey privateKey) throws Exception {
+        // Create a Signature object for signing with the DSA algorithm and SHA-256
+        Signature signature = Signature.getInstance("SHA256withDSA");
+
+        // Initialize the Signature object with the private key
+        signature.initSign(privateKey);
+
+        // Add the data to be signed
+        signature.update(message);
+
+        // Sign the data and return the digital signature
+        return signature.sign();
+    }
+
+    /**
+     * Verifies a digital signature using a public key.
+     *
+     * @param message   the original message data
+     * @param signature the digital signature to verify
+     * @param publicKey the public key used for verification
+     * @return true if the signature is valid, false otherwise
+     * @throws Exception if an error occurs during the verification process
+     */
+    public static boolean verifySignature(byte[] message, byte[] signature, PublicKey publicKey) throws Exception {
+        // Create a Signature object for verification with the DSA algorithm and SHA-256
+        Signature sig = Signature.getInstance("SHA256withDSA");
+
+        // Initialize the Signature object with the public key
+        sig.initVerify(publicKey);
+
+        // Add the data to be verified
+        sig.update(message);
+
+        // Verify the signature and return the result
+        return sig.verify(signature);
+    }
+}
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+package com.thealgorithms.hashes;
+
+import java.math.BigInteger;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.Scanner;
+
+/**
+ * The MD5 class provides a method to generate the MD5 hash for a given string.
+ * MD5 (Message Digest Algorithm 5) is a widely used cryptographic hash function that produces
+ * a 128-bit (16-byte) hash value. It is commonly used for checksums and data integrity,
+ * although it is no longer considered secure for cryptographic purposes.
+ * 
+ * @see <a href="https://en.wikipedia.org/wiki/MD5">MD5 on Wikipedia</a>
+ */
+public class MD5 {
+
+    /**
+     * Generates the MD5 hash of the input string.
+     *
+     * @param input the string to be hashed
+     * @return the MD5 hash as a hexadecimal string
+     */
+    public static String getMd5(String input) {
+        try {
+            // Create a MessageDigest instance for MD5
+            MessageDigest md = MessageDigest.getInstance("MD5");
+
+            // Compute the MD5 digest of the input string
+            byte[] messageDigest = md.digest(input.getBytes());
+
+            // Convert the byte array into a BigInteger to get the hash in hexadecimal format
+            BigInteger no = new BigInteger(1, messageDigest);
+
+            // Convert the BigInteger to a hexadecimal string
+            String hashtext = no.toString(16);
+
+            // Pad with leading zeros to ensure the hash is 32 characters long
+            while (hashtext.length() < 32) {
+                hashtext = "0" + hashtext;
+            }
+
+            // Return the generated MD5 hash
+            return hashtext;
+        } catch (NoSuchAlgorithmException e) {
+            // Handle the case where MD5 algorithm is not available
+            throw new RuntimeException(e);
+        }
+    }
+
+    /**
+     * The main method that takes user input, computes its MD5 hash, and prints the result.
+     *
+     * @param args command-line arguments
+     * @throws NoSuchAlgorithmException if the MD5 algorithm is not available
+     */
+    public static void main(String args[]) throws NoSuchAlgorithmException {
+        // Create a Scanner object to read input from the user
+        Scanner scanner = new Scanner(System.in);
+
+        // Prompt the user to enter a string to hash
+        System.out.print("Enter the string to hash: ");
+
+        // Read the input string from the user
+        String s = scanner.nextLine();
+
+        // Compute the MD5 hash of the input string and print it
+        System.out.println("Your HashCode Generated by MD5 is: " + getMd5(s));
+
+        // Close the Scanner object
+        scanner.close();
+    }
+}
@@ -0,0 +1,73 @@
+package com.thealgorithms.hashes;
+
+import java.math.BigInteger;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.Scanner;
+
+/**
+ * The SHA1 class provides a method to generate the SHA-1 hash for a given string.
+ * SHA-1 (Secure Hash Algorithm 1) is a cryptographic hash function that produces
+ * a 160-bit (20-byte) hash value. It is commonly used for data integrity verification,
+ * although it is no longer considered secure for cryptographic purposes.
+ * 
+ * @see <a href="https://en.wikipedia.org/wiki/SHA-1">SHA-1 on Wikipedia</a>
+ */
+public class SHA1 {
+
+    /**
+     * Generates the SHA-1 hash of the input string.
+     *
+     * @param input the string to be hashed
+     * @return the SHA-1 hash as a hexadecimal string
+     */
+    public static String getSha1(String input) {
+        try {
+            // Create a MessageDigest instance for SHA-1
+            MessageDigest md = MessageDigest.getInstance("SHA-1");
+
+            // Compute the SHA-1 digest of the input string
+            byte[] messageDigest = md.digest(input.getBytes());
+
+            // Convert the byte array into a BigInteger to get the hash in hexadecimal format
+            BigInteger no = new BigInteger(1, messageDigest);
+
+            // Convert the BigInteger to a hexadecimal string
+            String hashtext = no.toString(16);
+
+            // Pad with leading zeros to ensure the hash is 32 characters long
+            while (hashtext.length() < 32) {
+                hashtext = "0" + hashtext;
+            }
+
+            // Return the generated SHA-1 hash
+            return hashtext;
+        } catch (NoSuchAlgorithmException e) {
+            // Handle the case where SHA-1 algorithm is not available
+            throw new RuntimeException(e);
+        }
+    }
+
+    /**
+     * The main method that takes user input, computes its SHA-1 hash, and prints the result.
+     *
+     * @param args command-line arguments
+     * @throws NoSuchAlgorithmException if the SHA-1 algorithm is not available
+     */
+    public static void main(String args[]) throws NoSuchAlgorithmException {
+        // Create a Scanner object to read input from the user
+        Scanner scanner = new Scanner(System.in);
+
+        // Prompt the user to enter a string to hash
+        System.out.print("Enter the string to hash: ");
+
+        // Read the input string from the user
+        String s = scanner.nextLine();
+
+        // Compute the SHA-1 hash of the input string and print it
+        System.out.println("Your HashCode Generated by SHA-1 is: " + getSha1(s));
+
+        // Close the Scanner object
+        scanner.close();
+    }
+}
@@ -0,0 +1,96 @@
+package com.thealgorithms.hashes;
+
+import java.security.*;
+import java.util.Base64;
+import java.util.Scanner;
+
+/**
+ * The DSS class demonstrates the use of the Digital Signature Algorithm (DSA) for signing and verifying messages.
+ * DSA is a Federal Information Processing Standard for digital signatures, based on the mathematical concept of modular exponentiation and discrete logarithms.
+ * 
+ * @see <a href="https://en.wikipedia.org/wiki/Digital_Signature_Algorithm">Digital Signature Algorithm on Wikipedia</a>
+ */
+public class DSS {
+
+    public static void main(String[] args) throws Exception {
+        // Generate a key pair (public and private keys) for DSA
+        KeyPair keyPair = generateKeyPair();
+
+        // Get message input from the user
+        Scanner scanner = new Scanner(System.in);
+        System.out.print("Enter the message to sign: ");
+        String message = scanner.nextLine();
+        scanner.close();
+
+        // Sign the message using the private key
+        byte[] signature = signMessage(message.getBytes(), keyPair.getPrivate());
+        System.out.println("Signature: " + Base64.getEncoder().encodeToString(signature));
+
+        // Verify the signature using the public key
+        boolean verified = verifySignature(message.getBytes(), signature, keyPair.getPublic());
+        System.out.println("Signature verified: " + verified);
+    }
+
+    /**
+     * Generates a DSA key pair (private and public keys).
+     *
+     * @return a KeyPair containing a DSA private key and public key
+     * @throws NoSuchAlgorithmException if the DSA algorithm is not available
+     */
+    public static KeyPair generateKeyPair() throws NoSuchAlgorithmException {
+        // Create a KeyPairGenerator for DSA
+        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("DSA");
+
+        // Initialize the KeyPairGenerator with a key size and a secure random number generator
+        SecureRandom secureRandom = new SecureRandom();
+        keyPairGenerator.initialize(1024, secureRandom);
+
+        // Generate and return the KeyPair
+        return keyPairGenerator.generateKeyPair();
+    }
+
+    /**
+     * Signs a message using a private key.
+     *
+     * @param message    the message to be signed
+     * @param privateKey the private key used to sign the message
+     * @return a byte array containing the digital signature
+     * @throws Exception if an error occurs during the signing process
+     */
+    public static byte[] signMessage(byte[] message, PrivateKey privateKey) throws Exception {
+        // Create a Signature object for signing with the DSA algorithm and SHA-256
+        Signature signature = Signature.getInstance("SHA256withDSA");
+
+        // Initialize the Signature object with the private key
+        signature.initSign(privateKey);
+
+        // Add the data to be signed
+        signature.update(message);
+
+        // Sign the data and return the digital signature
+        return signature.sign();
+    }
+
+    /**
+     * Verifies a digital signature using a public key.
+     *
+     * @param message   the original message data
+     * @param signature the digital signature to verify
+     * @param publicKey the public key used for verification
+     * @return true if the signature is valid, false otherwise
+     * @throws Exception if an error occurs during the verification process
+     */
+    public static boolean verifySignature(byte[] message, byte[] signature, PublicKey publicKey) throws Exception {
+        // Create a Signature object for verification with the DSA algorithm and SHA-256
+        Signature sig = Signature.getInstance("SHA256withDSA");
+
+        // Initialize the Signature object with the public key
+        sig.initVerify(publicKey);
+
+        // Add the data to be verified
+        sig.update(message);
+
+        // Verify the signature and return the result
+        return sig.verify(signature);
+    }
+}