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package lab9;
import java.security.Key;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.Security;
import java.security.SecureRandom;
import javax.crypto.Cipher;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import javax.crypto.BadPaddingException;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.ShortBufferException;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import javax.rmi.CORBA.Util;
/**
 *
 * @author student
 */
public class Lab9 {
    public static void main(String[] args) throws Exception {
        byte[] keyBytes = new byte[16];
        byte[] keyBytes2 = new byte[16];
        // declare secure PRNG
        IvParameterSpec ob = new IvParameterSpec(keyBytes2);
        SecureRandom myPRNG = new SecureRandom();
        // seed the key
        myPRNG.nextBytes(keyBytes);
        // build the key from random key bytes
        SecretKeySpec myKey = new SecretKeySpec(keyBytes, "AES");
        // instantiate AES object for ECB with no padding
        Cipher myAES = Cipher.getInstance("AES/ECB/NoPadding");
        // initialize AES objecy to encrypt mode
        myAES.init(Cipher.ENCRYPT_MODE, myKey,ob);
        // initialize plaintext
        byte[] plaintext = new byte[16];
        //initialize ciphertext
        byte[] ciphertext = new byte[16];
        // update cipher with the plaintext
        int cLength = myAES.update(plaintext, 0, plaintext.length, ciphertext, 0);
        // process remaining blocks of plaintext
        cLength += myAES.doFinal(ciphertext, cLength);
        // print plaintext and ciphertext
        System.out.println("plaintext: " + javax.xml.bind.DatatypeConverter.printHexBinary(plaintext));
        System.out.println("ciphertext: " + javax.xml.bind.DatatypeConverter.printHexBinary(ciphertext));
        // initialize AES for decryption
        myAES.init(Cipher.DECRYPT_MODE, myKey,ob);
        // initialize a new array of bytes to place the decryption
        byte[] dec_plaintext = new byte[16];
        cLength = myAES.update(ciphertext, 0, ciphertext.length, dec_plaintext, 0);
        // process remaining blocks of ciphertext
        cLength += myAES.doFinal(dec_plaintext, cLength);
        // print the new plaintext (hopefully identical to the initial one)
        System.out.println("decrypted: " + javax.xml.bind.DatatypeConverter.printHexBinary(dec_plaintext));
        // get a Cipher instance for RSA with PKCS1 padding
        Cipher myRSA = Cipher.getInstance("RSA/ECB/PKCS1Padding");
        // get an instance for the Key Generator
        KeyPairGenerator myRSAKeyGen = KeyPairGenerator.getInstance("RSA");
        // generate an 1024 bit key
        myRSAKeyGen.initialize(1024, myPRNG);
        KeyPair myRSAKeyPair= myRSAKeyGen.generateKeyPair();
        // store the public and private key individually
        Key pbKey = myRSAKeyPair.getPublic();
        Key pvKey = myRSAKeyPair.getPrivate();
        // init cipher for encryption
        myRSA.init(Cipher.ENCRYPT_MODE, pbKey, myPRNG);
        // encrypt, as expected we encrypt a symmetric key with RSA rather than a file or some longer stream which should be encrypted with AES
        ciphertext = myRSA.doFinal(keyBytes);
        // init cipher for decryption
        myRSA.init(Cipher.DECRYPT_MODE, pvKey);
        // decrypt
        plaintext = myRSA.doFinal(ciphertext);
        System.out.println("plaintext: " + javax.xml.bind.DatatypeConverter.printHexBinary(plaintext));
        System.out.println("ciphertext: " + javax.xml.bind.DatatypeConverter.printHexBinary(ciphertext));
        System.out.println("keybytes: " + javax.xml.bind.DatatypeConverter.printHexBinary(keyBytes));
    }

}