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8.2

AES Decryption in C#

Asked by raheelasadkhan in C# Programming Language, Miscellaneous Security, .NET

Tags: aes, c#, .net, java

I have the following data. Each line has been encrypted using AES encryption in Java. The objective is to decrypt the same in C#. The Java code that encrypts is listed below. The key file generated by the Java code is also attached here (Please rename extension to .DAT).

I am not sure but I think that the last four characters are not part of the encrypted data.

4A675E034589E7FEAA1A9D3695044B9D]en]
827D3D22560C07ECF952DDC754E2FA59]en]
BF6040BD3F918BB58E09E0F4904D59A2]en]
A0C7DA329023435BB21FADEED79056AB]en]
58D8CA901DDB662590FCD61EBC538100]en]
7D7076896765CDDF83FC6B1C16BB8912]en]
AA4EE36240E3863A6126995D18B2FADF]en]
9473448BE9B664894B5760D07DD1264F]en]
CD756F597FCD3584EB942A31D7014E1A]en]
1522C008CF31B421C1B078989F384389]en]

DF3AF67774360E267ED4E8DF5E367075]en]
4DB4D36B7F1729C907A391C3B9F8E274]en]
07007DFA89924CEA1A0D1BDC0C1E1A0D]en]
7AF269B0AE8BEFF4AA91DB36161D36D4]en]
7200804B1612E11BD97C3F878821B8BF]en]
F44EA7B2BC892F2A3BB0F21B03045C42]en]
AB584DC3CFB9AFFA3475FA0BD78EA06E]en]
6FDDDCE7EE39DC6F2CC0527A3F20299A]en]
FF5A6F59CA7A508395B6242A67885725]en]
816AF23A648B807EE993EBC3B8A0866D]en]

819857F1A4E800CF862C32CBA271758D]en]
9FFD6731346E3C7B0AD0ED26441D6F2C]en]
A66EFBFA93D1DE2EB55B3A7ECD1D971E]en]
1EF541C76DDCC778CBCB8D82F05AE53D]en]
555B44DFC01A14545E57411EA735E368]en]
566B2E70E5ED497486B6D4AA637CD372]en]
402845E886C16484A4C7B3B96CD66FBA]en]
E45B5F2BE592033733A1B6A5BCCC92AF]en]
CE3E764E4D2E0509C98047D02EB6B1AB]en]
913F2BFF90AA90B9A015BEA790AF64A0]en]
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package Emfasis; 
import java.security.*;
import javax.crypto.*;
import javax.crypto.spec.*;
import java.io.*;
import java.io.FileOutputStream;
import java.text.*; 
import javax.swing.JOptionPane; 
public class ModelEngine
{
    public static String reportName ="";
    public static ObjectOutputStream outKey;
    public static Key keyFromFile;
    SimpleDateFormat dateFormat = new SimpleDateFormat("dd-MMM-yyHHmmss");
    public  static char[] hexChar =
    {
        '0' , '1' , '2' , '3' ,
        '4' , '5' , '6' , '7' ,
        '8' , '9' , 'A' , 'B' ,
        'C' , 'D' , 'E' , 'F'
    }; 

    /**
    * Turns array of bytes into string
    *
    * @param buf	Array of bytes to convert to hex string
    * @return	Generated hex string
    */
    public static String asHex (byte buf[])
    {
        int i;
        StringBuffer strbuf = new StringBuffer(buf.length * 2); 
        for (i = 0; i < buf.length; i++)
        {
            if (((int) buf[i] & 0xff) < 0x10)
                strbuf.append("0"); 
            strbuf.append(Long.toString((int) buf[i] & 0xff, 16));
        } 
        return strbuf.toString();
    } 
    public String generateAndStoreKey(String dirPath)
    {
        //=================================================
        // Generate the secret key specs.
        long keyId = System.currentTimeMillis(); 
        try
        {
            KeyGenerator kgen = KeyGenerator.getInstance("AES");
            kgen.init(128); // 192 and 256 bits may not be available
            SecretKey skey = kgen.generateKey(); 
            //generate random three letter String
            double randomNumber;
            double randomNumberSetup;
            char randomCharacter;
            String str = ""; 
            for (int i = 0; i < 3; i++)
            {
                randomNumber = Math.random();
                randomNumberSetup = (randomNumber * 26 + 'a');
                randomCharacter = (char) randomNumberSetup;
                System.out.print(randomCharacter + ": ");
                str += randomCharacter;
            } 
            //System.out.println(" - Random string is(" + str + ")");
            String reportFile = dirPath+System.getProperty("file.separator")+"ENCKey" + dateFormat.format(new java.util.Date())+"-"+str.toUpperCase()+".DAT";
            // System.err.println(reportFile);
            outKey = new ObjectOutputStream(new FileOutputStream(reportFile));// create serialized output stream
            outKey.writeObject(skey);              								  // write key in a file
            this.reportName = reportFile;
            outKey.close();
        }
        catch (Exception e)
        {
            e.printStackTrace();
            JOptionPane.showMessageDialog(null,"<<Operational Error! >> \n Failed to generate key file.","eMedXchange 1.0",JOptionPane.ERROR);
            return null;
        } 
        return reportName;
    } 
    public String getReprtFile()
    {
        return reportName;
    } 
    public String  saveRowToFile(String keyLocatn,String rowForSave,boolean encrypIndicator)
    {
        FileOutputStream encryptedOutPutFile = null;
        long keyId = System.currentTimeMillis();
        String userHomeDir = System.getProperty("user.home"); 
        try
        {
            KeyGenerator kgen = KeyGenerator.getInstance("AES");
            kgen.init(128); // 192 and 256 bits may not be available
            SecretKey skey = kgen.generateKey();
            String encryptedFile = userHomeDir + System.getProperty("file.separator") + "med" + keyId + ".dat";
            encryptedOutPutFile = new FileOutputStream(new File(encryptedFile));
            // encryptedOutPutFile
            try
            {
                ObjectInputStream keyIn = new ObjectInputStream(new FileInputStream(keyLocatn));  // open key file
                keyFromFile = (Key) keyIn.readObject();  // read key from file
                keyIn.close();
            }
            catch(Exception e)
            {
                e.printStackTrace();
            } 
            byte[] raw = keyFromFile.getEncoded();
            SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
            // Instantiate the cipher 
            Cipher cipher = Cipher.getInstance("AES");
            cipher.init(Cipher.ENCRYPT_MODE, skeySpec); 
            //===============
            String[] values = rowForSave.split("\\|");
            //DO better presentation here///////////////////////
            //check for more methods of cypher
            for (String str : values)
            {
                if(encrypIndicator)
                {
                    byte[] encrypted = cipher.doFinal(str.getBytes());
                    encryptedOutPutFile.write(encrypted);//save bytes encrypted to file
                    // System.out.println("encrypted string: " + asHex(encrypted));
                    // System.out.println(str);
                }
                else
                {
                    encryptedOutPutFile.write(str.getBytes());//save bytes unencrypted to file
                }
            } 
            //====================
            encryptedOutPutFile.close();
        }
        catch(Exception e)
        {
            e.printStackTrace();
            return "FALURE";
        } 
        return "SUCCESS";
    } 
    public String saveHeadingsToFile(String keyLocatn,String headingForSave,boolean encrypIndicator)
    {
        String[] values = headingForSave.split("\\|"); 
        for (String str : values)
        {
            System.out.println(str);
        } 
        return null;
    } 
    public String encryptAndSaveFile(Key key,String fileLocation)
    {
        //Read the lines into a StringBuffer,convert to String and encrypts
        String userHomeDir = System.getProperty("user.home");
        byte[] aesKey; 
        String result= null;
        try
        {
            Cipher cipher = Cipher.getInstance("AES");
            aesKey = key.getEncoded();
            SecretKeySpec keySpec = new SecretKeySpec(aesKey, "AES");
            cipher.init(Cipher.ENCRYPT_MODE, keySpec); 
            FileInputStream fis = new FileInputStream(new File(fileLocation));
            CipherInputStream cis = new CipherInputStream(fis, cipher); 
            FileOutputStream fos = new FileOutputStream(new File(userHomeDir + System.getProperty("file.separator") + "md_e.txt"));
            byte[] b = new byte[8];
            int i;
            while ((i = cis.read(b)) != -1)
            {
                fos.write(b, 0, i);
            }
            fos.flush();
            fos.close();
            result = "SUCCESS";
        }
        catch(Exception e)
        {
            JOptionPane.showMessageDialog(null,"<<Operational Error!.Failed to encrypt file>>\nPlease check the input files.","MedRecord Track",JOptionPane.ERROR_MESSAGE);
            e.printStackTrace();
            result = "FAILURE";
        } 
        return result;
    } 
    public String decryptAndSaveFile(Key key,String fileLocation)
    {
        //Read the lines into a StringBuffer,convert to String and decrypts//another option
        String userHomeDir = System.getProperty("user.home");
        byte[] aesKey;
        String result= null;
        try
        {
            // Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            Cipher cipher = Cipher.getInstance("AES");
            aesKey = key.getEncoded();
            SecretKeySpec keySpec = new SecretKeySpec(aesKey, "AES");
            cipher.init(Cipher.DECRYPT_MODE, keySpec); 
            FileInputStream fis = new FileInputStream(new File(fileLocation));
            CipherInputStream cis = new CipherInputStream(fis, cipher);
            FileOutputStream fos = new FileOutputStream(new File(userHomeDir+System.getProperty("file.separator")+"MedicalData_Ana_Decrypted.txt")); 
            byte[] b = new byte[8];
            int i; 
            while ((i = cis.read(b)) != -1)
            {
                fos.write(b, 0, i);
            }
            fos.flush();
            fos.close();
            cis.close();
            fis.close();
            result= "SUCCESS";
        }
        catch(Exception e)
        {
            JOptionPane.showMessageDialog(null,"<<Operational Error! \nFailed to decrypt file>>\nPlease check the input files.","MedRecord Track",JOptionPane.ERROR);
            e.printStackTrace();
            result= "FAILURE";
        } 
        return result;
    } 
    public static byte[] toBinArray (String hexStr)
    {
        byte bArray[] = new byte[hexStr.length()/2]; 
        for(int i=0; i<(hexStr.length()/2); i++)
        {
            byte firstNibble  = Byte.parseByte(hexStr.substring(2*i,2*i+1),16); // [x,y)
            byte secondNibble = Byte.parseByte(hexStr.substring(2*i+1,2*i+2),16);
            int finalByte = (secondNibble) | (firstNibble << 4 ); // bit-operations only with numbers, not bytes.
            bArray[i] = (byte) finalByte;
        } 
        return bArray;
    } 
    public static String toHexString( byte[] b )
    {
        StringBuffer sb = new StringBuffer( b.length * 2 ); 
        for ( int i=0; i<b.length; i++ )
        {
            // look up high nibble char
            sb.append( hexChar [( b[i] & 0xf0 ) >>> 4] ); // fill left with zero bits
            // look up low nibble char
            sb.append( hexChar [b[i] & 0x0f] );
        } 
        return sb.toString();
    } 
    public String encryptStringPart(Key key,String strPart)
    {
        byte[] encrypted = null ;
        try
        {
            byte[] aesKey = key.getEncoded();
            SecretKeySpec skeySpec = new SecretKeySpec(aesKey, "AES"); 
            // Instantiate the cipher
            //   Cipher cipher = Cipher.getInstance("AES");
            //Try explicitly stating a mode and padding
            //look up what modes and padding is available. 
            // Cipher cipher  = Cipher.getInstance("AES/ECB/PKCS5Padding");//my new
            Cipher cipher  = Cipher.getInstance("AES");
            cipher.init(Cipher.ENCRYPT_MODE, skeySpec); 
            encrypted = cipher.doFinal(strPart.getBytes());
            // System.out.println("encrypted string: " + asHex(encrypted));
        }
        catch(Exception e )
        {
            e.printStackTrace();
        }
        ///New Test
        //Convert the encrpted byte[] to String
        String stringFromEncr = toHexString(encrypted);////will need
        // System.out.println("\n stringFromEncr: " + stringFromEncr);//I will need this 
        return stringFromEncr;
    } 
    public String decryptStringPart(Key key,String strPart)
    {
        byte[] decrypted = null ;
        String decreString = null; 
        try
        {
            byte[] aesKey = key.getEncoded();
            SecretKeySpec skeySpec = new SecretKeySpec(aesKey, "AES"); 
            // Cipher cipher  = Cipher.getInstance("AES/ECB/PKCS5Padding");
            Cipher cipher  = Cipher.getInstance("AES");
            cipher.init(Cipher.DECRYPT_MODE, skeySpec); 
            String hexString = strPart.substring(0, strPart.length()-4);//Begining of "]en]" marker
            byte[] decodedBinary = toBinArray(hexString);
            //Then Hex
            decrypted = cipher.doFinal(decodedBinary);
            decreString = new String(decrypted);
            // System.out.println("XXXXXX decrypted string:XXXXXX " + decreString);
        }
        catch(Exception e )
        {
            e.printStackTrace();
        } 
        return decreString;
    } 
}
Attachments:
 
ENCKey.txt (141 bytes) (Possible File Type Mismatch) 
Please rename the extension to .DAT
 
 
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[+][-]11/08/09 04:16 AM, ID: 25770248Accepted Solution

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Zones: C# Programming Language, Miscellaneous Security, .NET
Tags: aes, c#, .net, java
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Solution Provided By: raheelasadkhan
Participating Experts: 1
Solution Grade: A
 
[+][-]11/04/09 05:23 AM, ID: 25739001Expert Comment

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[+][-]11/04/09 05:57 AM, ID: 25739308Author Comment

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