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package org.owasp.crypto;

import javax.crypto.KeyGenerator;import javax.crypto.SecretKey;import javax.crypto.Cipher;import java.security.Key;

import java.security.NoSuchAlgorithmException;import java.security.InvalidKeyException;import java.security.InvalidAlgorithmParameterException;import javax.crypto.NoSuchPaddingException;import javax.crypto.BadPaddingException;import javax.crypto.IllegalBlockSizeException;

import sun.misc.BASE64Encoder;

/*** @author Joe Prasanna Kumar* This program provides the following cryptographic functionalities* 1. Encryption using AES* 2. Decryption using AES** High Level Algorithm :* 1. Generate a DES key (specify the Key size during this phase)

* 2. Create the Cipher* 3. To Encrypt : Initialize the Cipher for Encryption* 4. To Decrypt : Initialize the Cipher for Decryption***/

public class SymmetricEncrypt {String strDataToEncrypt = new String();String strCipherText = new String();String strDecryptedText = new String();static KeyGenerator keyGen;

private static String strHexVal = "0123456789abcdef";

public static SecretKey getSecret(){/*** Step 1. Generate an AES key using KeyGenerator* Initialize the keysize to 128**/

try{keyGen = KeyGenerator.getInstance("AES");keyGen.init(128);

}

catch(Exception exp){System.out.println(" Exception inside constructor " +exp);

}

SecretKey secretKey = keyGen.generateKey();return secretKey;

}

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/*** Step2. Create a Cipher by specifying the following parameters* a. Algorithm name - here it is AES*/

public byte[] encryptData(byte[] byteDataToEncrypt, Key secretKey, String Algorithm) {

byte[] byteCipherText = new byte[200];

try {Cipher aesCipher = Cipher.getInstance(Algorithm);

/*** Step 3. Initialize the Cipher for Encryption*/if(Algorithm.equals("AES")){aesCipher.init(Cipher.ENCRYPT_MODE,secretKey,aesCipher.getParameters());}else if(Algorithm.equals("RSA/ECB/PKCS1Padding")){aesCipher.init(Cipher.ENCRYPT_MODE,secretKey);}

/*** Step 4. Encrypt the Data* 1. Declare / Initialize the Data. Here the data is of type String* 2. Convert the Input Text to Bytes* 3. Encrypt the bytes using doFinal method*/

byteCipherText = aesCipher.doFinal(byteDataToEncrypt);strCipherText = new BASE64Encoder().encode(byteCipherText);

}

catch (NoSuchAlgorithmException noSuchAlgo){

System.out.println(" No Such Algorithm exists " + noSuchAlgo);}

catch (NoSuchPaddingException noSuchPad){System.out.println(" No Such Padding exists " + noSuchPad);}

catch (InvalidKeyException invalidKey){System.out.println(" Invalid Key " + invalidKey);

}

catch (BadPaddingException badPadding){System.out.println(" Bad Padding " + badPadding);

}

catch (IllegalBlockSizeException illegalBlockSize){System.out.println(" Illegal Block Size " + illegalBlockSize);illegalBlockSize.printStackTrace();

}

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catch (Exception exp){exp.printStackTrace();

}return byteCipherText;}/*** Step 5. Decrypt the Data* 1. Initialize the Cipher for Decryption* 2. Decrypt the cipher bytes using doFinal method*/

public byte[] decryptData(byte[] byteCipherText, Key secretKey, String Algorit

hm) {byte[] byteDecryptedText = new byte[200];

try{

Cipher aesCipher = Cipher.getInstance(Algorithm);if(Algorithm.equals("AES")){aesCipher.init(Cipher.DECRYPT_MODE,secretKey,aesCipher.getParameters());}else if(Algorithm.equals("RSA/ECB/PKCS1Padding")){aesCipher.init(Cipher.DECRYPT_MODE,secretKey);

}

byteDecryptedText = aesCipher.doFinal(byteCipherText);strDecryptedText = new String(byteDecryptedText);}

catch (NoSuchAlgorithmException noSuchAlgo){System.out.println(" No Such Algorithm exists " + noSuchAlgo);

}

catch (NoSuchPaddingException noSuchPad){

System.out.println(" No Such Padding exists " + noSuchPad);}

catch (InvalidKeyException invalidKey){System.out.println(" Invalid Key " + invalidKey);invalidKey.printStackTrace();}

catch (BadPaddingException badPadding){System.out.println(" Bad Padding " + badPadding);badPadding.printStackTrace();

}

catch (IllegalBlockSizeException illegalBlockSize){System.out.println(" Illegal Block Size " + illegalBlockSize);illegalBlockSize.printStackTrace();}

catch (InvalidAlgorithmParameterException invalidParam){

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System.out.println(" Invalid Parameter " + invalidParam);}

return byteDecryptedText;}

public static byte[] convertStringToByteArray(String strInput) {strInput = strInput.toLowerCase();byte[] byteConverted = new byte[(strInput.length() + 1) / 2];int j = 0;int interimVal;int nibble = -1;

for (int i = 0; i < strInput.length(); ++i) {interimVal = strHexVal.indexOf(strInput.charAt(i));if (interimVal >= 0) {if (nibble < 0) {nibble = interimVal;

} else {byteConverted[j++] = (byte) ((nibble = 0) {byteConverted[j++] = (byte) (nibble >> 4) & 0xf));buf.append(strHexVal.charAt(block[i] & 0xf));

}

return buf.toString();}

}