1. // Java program to create a
2. // asymmetric key
3.  
4.  
5. import java.security.KeyPair;
6. import java.security.KeyPairGenerator;
7. import java.security.PrivateKey;
8. import java.security.PublicKey;
9. import java.security.SecureRandom;
10. import java.util.Scanner;
11.  
12. import javax.crypto.Cipher;
13. // Class to create an asymmetric key
14.  
15. public class Asymmetric {
16.      private static final String RSA = "RSA";//algoritmo rsa
17.  
18.     // Generating public and private key
19.     // using RSA algorithm.
20.  
21.     public static KeyPair generateRSAKkeyPair()throws Exception{
22.         SecureRandom secureRandom = new SecureRandom(); //random  ma più sicuro
23.         KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(RSA);//crea una chiave da usare per l'rsa
24.        
25.         keyPairGenerator.initialize(2048, secureRandom);//keysize
26.         return keyPairGenerator.generateKeyPair();//crea la coppia d chiavi
27.  
28.     }
29.    
30.     // Encryption function which converts
31.     // the plainText into a cipherText
32.     // using private Key.
33.     public static byte[] do_RSAEncryption(String plainText,PrivateKey privateKey) throws Exception
34.     {
35.         Cipher cipher = Cipher.getInstance(RSA);
36.  
37.         cipher.init(Cipher.ENCRYPT_MODE, privateKey);
38.  
39.         return cipher.doFinal(plainText.getBytes());
40.     }
41.  
42.     // Decryption function which converts
43.     // the ciphertext back to the
44.     // original plaintext.
45.     public static String do_RSADecryption(byte[] cipherText,PublicKey publicKey)throws Exception{
46.         Cipher cipher = Cipher.getInstance(RSA);
47.         cipher.init(Cipher.DECRYPT_MODE,publicKey);
48.         byte[] result = cipher.doFinal(cipherText);
49.         return new String(result);
50.     }
51.  
52.     // Driver code
53.  
54.     public static void main(String args[]) throws Exception {
55.         KeyPair keypair = generateRSAKkeyPair();
56.         //RSA private keys are encoded in PKCS#8 format, and public keys are encoded in X.509 format
57.         //DatatypeConverter.printHexBinary
58.         //chiavi
59.         System.out.println("Public Key is: " + keypair.getPublic().getEncoded());
60.  
61.         System.out.println("Private Key is: " + keypair.getPrivate().getEncoded());
62.  
63.         String plainText = "This is the PlainText I want to Encrypt using RSA.";
64.        
65.         byte[] cipherText= do_RSAEncryption(plainText,keypair.getPrivate());
66.        
67.         System.out.print("The Encrypted Text is: ");
68.  
69.         System.out.println(cipherText);
70.  
71.         String decryptedText = do_RSADecryption(cipherText,keypair.getPublic());
72.  
73.         System.out.println("The decrypted text is: "+ decryptedText);
74.     }
75. }
76.        
77.        
78.