// Java program to create a
// asymmetric key
 

import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.util.Scanner;
 
import javax.crypto.Cipher;
// Class to create an asymmetric key

public class Asymmetric {
     private static final String RSA = "RSA";//algoritmo rsa

    // Generating public and private key
    // using RSA algorithm.

    public static KeyPair generateRSAKkeyPair()throws Exception{
        SecureRandom secureRandom = new SecureRandom(); //random  ma più sicuro
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(RSA);//crea una chiave da usare per l'rsa
        
        keyPairGenerator.initialize(2048, secureRandom);//keysize
        return keyPairGenerator.generateKeyPair();//crea la coppia d chiavi

    }
    
    // Encryption function which converts
    // the plainText into a cipherText
    // using private Key.
    public static byte[] do_RSAEncryption(String plainText,PrivateKey privateKey) throws Exception
    {
        Cipher cipher = Cipher.getInstance(RSA);
 
        cipher.init(Cipher.ENCRYPT_MODE, privateKey);
 
        return cipher.doFinal(plainText.getBytes());
    }
 
    // Decryption function which converts
    // the ciphertext back to the
    // original plaintext.
    public static String do_RSADecryption(byte[] cipherText,PublicKey publicKey)throws Exception{
        Cipher cipher = Cipher.getInstance(RSA);
        cipher.init(Cipher.DECRYPT_MODE,publicKey);
        byte[] result = cipher.doFinal(cipherText);
        return new String(result);
    }

    // Driver code

    public static void main(String args[]) throws Exception {
        KeyPair keypair = generateRSAKkeyPair();
        //RSA private keys are encoded in PKCS#8 format, and public keys are encoded in X.509 format
        //DatatypeConverter.printHexBinary
        //chiavi
        System.out.println("Public Key is: " + keypair.getPublic().getEncoded());
 
        System.out.println("Private Key is: " + keypair.getPrivate().getEncoded());

        String plainText = "This is the PlainText I want to Encrypt using RSA.";
        
        byte[] cipherText= do_RSAEncryption(plainText,keypair.getPrivate());
        
        System.out.print("The Encrypted Text is: ");
 
        System.out.println(cipherText);
 
        String decryptedText = do_RSADecryption(cipherText,keypair.getPublic());
 
        System.out.println("The decrypted text is: "+ decryptedText);
    }
}