RSA Algorithim to encrypt and decrypt given String

Author: shreyashghag

RSA.java

@@ -0,0 +1,49 @@
+import java.security.KeyPair;
+import java.security.KeyPairGenerator;
+import java.security.NoSuchAlgorithmException;
+import java.security.PrivateKey;
+import java.security.PublicKey;
+
+import javax.crypto.Cipher;
+import java.util.*;
+public class RSA {
+    
+    public static void main(String [] args) throws Exception {
+        // generate public and private keys
+        KeyPair keyPair = buildKeyPair();
+        PublicKey pubKey = keyPair.getPublic();
+        PrivateKey privateKey = keyPair.getPrivate();
+        
+        // encrypt the message
+		System.out.println("Enter message");
+		Scanner sc =new Scanner(System.in);
+		String msg=sc.next();
+        byte [] encrypted = encrypt(privateKey,msg);     
+        System.out.println("Encrypted String: "+new	String(encrypted));  // <<encrypted message>>
+        
+        // decrypt the message
+        byte[] secret = decrypt(pubKey, encrypted);                                 
+        System.out.println("decrypted String: "+new String(secret));     // This is a secret message
+    }
+
+    public static KeyPair buildKeyPair() throws NoSuchAlgorithmException {
+        final int keySize = 2048;
+        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
+        keyPairGenerator.initialize(keySize);      
+        return keyPairGenerator.genKeyPair();
+    }
+
+    public static byte[] encrypt(PrivateKey privateKey, String message) throws Exception {
+        Cipher cipher = Cipher.getInstance("RSA");  
+        cipher.init(Cipher.ENCRYPT_MODE, privateKey);  
+
+        return cipher.doFinal(message.getBytes());  
+    }
+    
+    public static byte[] decrypt(PublicKey publicKey, byte [] encrypted) throws Exception {
+        Cipher cipher = Cipher.getInstance("RSA");  
+        cipher.init(Cipher.DECRYPT_MODE, publicKey);
+        
+        return cipher.doFinal(encrypted);
+    }
+}