Question regarding encryption and decryption

Hi all,
I am doing a authentication project. In which I do encryption and decryption (AES 128 bit) in two different methods. At the time of encryption (for eg a text file ), I store the key in dat file (key.dat). And at the time of decryption, I read the key.dat and extract the key and do the decryption. This works fine. No problem with that.
But the problem is, that the client requires that
"No encryption keys will be written to the hard drive."
I have to store the key somewhere to decrypt the encrypted file. Right. Without storing the key, I cannot decrypt.
The question is (though its a foolish question) with out storing the key, can i encrypt and decrypt (in two different methods) the text file ?
Thank You.
Regards,
Jay

Hi Grant,
Thanks for the reply. ( I am the one whom you helped to solve the encryption and decryption problem using AES )
I will give you an overview of my project. Its an Two Factor Authentication using an USB Flash Drive.
Admin Side : ( currently developing this part )
Through an CPP executable file ( writen by John Hyde USB By Example author), I retrive the Manufature ID, Product ID and Serial number of the USB Flash Drive from a text file which is generated when the executable file is executed.
From my Java application, i retrive the Manufature ID, Product ID and Serial number.The admin (through an dialog box ) enters an usernam and password . All this information ( Manufature ID, Product ID, Serial number , username and password ) using AES 128 bit encryption i write these information to encrypted file in the USB Flash drive along with the the encryption key used at the time of decryption.
User Side: ( not yet devleoped )
When the user plugs in the USB Flash drive, an dialog box is shown where the user enters the username and password ( assigned earlier by the admin). This username and password is checked along with the Manufature ID, Product ID and Serial number encrypted earlier and stored in the USB Flash drive. If username password ,Manufature ID, Product ID and Serial number (retrieved again by exectuing the CPP excutable file ) are correct the user is granted access.
Whats your suggestion reagrading of storing the encryption key? I have to store the key in the USB Flash drive along with the encrypted file. But then wont an intruder (for eg ) if he gets the key and decrypt the file ?
Client has mentioned to use AES 128 Bit encryption.
Thank You.
Regards,
Jay.

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Problem in using socket streams with encryption and decryption

Hi,
I am developing a client/server program with encryption and decryption at both end. While sending a message from client it should be encrypted and at the receiving end(server) it should be decrypted and vice versa.
But while doing so i got a problem if i use both encryption and decryption at both ends. But If i use only encryption at one (only outputstream) and decryption at other end(only inputstream) there is no problem.
Here is client/server pair of programs in which i am encrypting the outputstream of the socket in client side and decrypting the inputstream of the socket in server side.
serverSocketDemo.java
import java.io.*;
import java.net.*;
import java.security.*;
import java.security.spec.*;
import javax.crypto.*;
import javax.crypto.spec.*;
import java.util.*;
import java.util.zip.*;
class serverSocketDemo
     public static void main(String args[])
          try
          {                    //server listening on port 2000
               ServerSocket server=new ServerSocket(2000);
               while (true)
                    Socket theConnection=server.accept();
                    System.out.println("Connecting from local address : "+theConnection.getLocalAddress());
                    System.out.println("Connection request from : "+theConnection.getInetAddress());
                    //Input starts from here
                    Reader in=new InputStreamReader(getNetInStream(theConnection.getInputStream()),"ASCII");
                    StringBuffer strbuf=new StringBuffer();
                    int c;
                    while (true)
                         c=in.read();
                         if(c=='\n' || c==-1)
                              break;
                         strbuf.append((char)c);
                    String str=strbuf.toString();
                    System.out.println("Message from Client : "+str);
                    in.close();
                    theConnection.close();
          catch(BindException e)
               System.out.println("The Port is in use or u have no privilage on this port");
          catch(ConnectException e)
               System.out.println("Connection is refused at remote host because the host is busy or no process is listening on that port");
          catch(IOException e)
               System.out.println("Connection disconnected");
          catch(Exception e)
     public static BufferedInputStream getNetInStream(InputStream in) throws Exception
          // register the provider that implements the algorithm
          Provider sunJce = new com.sun.crypto.provider.SunJCE( );
          Security.addProvider(sunJce);
          // create a key
          byte[] desKeyDataDec = "This encryption can not be decrypted".getBytes();
          DESKeySpec desKeySpecDec = new DESKeySpec(desKeyDataDec);
          SecretKeyFactory keyFactoryDec = SecretKeyFactory.getInstance("DES");
          SecretKey desKeyDec = keyFactoryDec.generateSecret(desKeySpecDec);
          // use Data Encryption Standard
          Cipher desDec = Cipher.getInstance("DES");
          desDec.init(Cipher.DECRYPT_MODE, desKeyDec);
          CipherInputStream cin = new CipherInputStream(in, desDec);
          BufferedInputStream bin=new BufferedInputStream(new GZIPInputStream(cin));
          return bin;
clientSocketDemo.java
import java.io.*;
import java.net.*;
import java.security.*;
import java.security.spec.*;
import javax.crypto.*;
import javax.crypto.spec.*;
import java.util.*;
import java.util.zip.*;
class clientSocketDemo
     public static void main(String args[])
          try
               Socket theConnection=new Socket("localhost",2000);
               System.out.println("Connecting from local address : "+theConnection.getLocalAddress());
               System.out.println("Connecting to : "+theConnection.getInetAddress());
               //Output starts from here
               OutputStream out=getNetOutStream(theConnection.getOutputStream());
               out.write("Please Welcome me\n".getBytes());
               out.flush();
               out.close();
               theConnection.close();
          catch(BindException e)
               System.out.println("The Port is in use or u have no privilage on this port");
          catch(ConnectException e)
               System.out.println("Connection is refused at remote host because the host is busy or no process is listening on that port");
          catch(IOException e)
               System.out.println("Connection disconnected");
          catch(Exception e)
     public static OutputStream getNetOutStream(OutputStream out) throws Exception
          // register the provider that implements the algorithm
          Provider sunJce = new com.sun.crypto.provider.SunJCE( );
          Security.addProvider(sunJce);
          // create a key
          byte[] desKeyDataEnc = "This encryption can not be decrypted".getBytes();
          DESKeySpec desKeySpecEnc = new DESKeySpec(desKeyDataEnc);
          SecretKeyFactory keyFactoryEnc = SecretKeyFactory.getInstance("DES");
          SecretKey desKeyEnc = keyFactoryEnc.generateSecret(desKeySpecEnc);
          // use Data Encryption Standard
          Cipher desEnc = Cipher.getInstance("DES");
          desEnc.init(Cipher.ENCRYPT_MODE, desKeyEnc);
          CipherOutputStream cout = new CipherOutputStream(out, desEnc);
          OutputStream outstream=new BufferedOutputStream(new GZIPOutputStream(cout));
          return outstream;
Here is client/server pair in which i use both encrypting outpustream and decrypting inputstream at both ends.
serverSocketDemo.java
import java.io.*;
import java.net.*;
import java.security.*;
import java.security.spec.*;
import javax.crypto.*;
import javax.crypto.spec.*;
import java.util.*;
import java.util.zip.*;
class serverSocketDemo
     private Cipher desEnc,desDec;
     serverSocketDemo()
          try
               // register the provider that implements the algorithm
               Provider sunJce = new com.sun.crypto.provider.SunJCE( );
               Security.addProvider(sunJce);
               // create a key
               byte[] desKeyData = "This encryption can not be decrypted".getBytes();
               DESKeySpec desKeySpec = new DESKeySpec(desKeyData);
               SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
               SecretKey desKey = keyFactory.generateSecret(desKeySpec);
               desEnc = Cipher.getInstance("DES");
               desEnc.init(Cipher.ENCRYPT_MODE, desKey);
               desDec = Cipher.getInstance("DES");
               desDec.init(Cipher.DECRYPT_MODE, desKey);
          catch (javax.crypto.NoSuchPaddingException e)
               System.out.println(e);
          catch (java.security.NoSuchAlgorithmException e)
               System.out.println(e);
          catch (java.security.InvalidKeyException e)
               System.out.println(e);
          catch(Exception e)
               System.out.println(e);
          startProcess();
     public void startProcess()
          try
               ServerSocket server=new ServerSocket(2000);
               while (true)
                    final Socket theConnection=server.accept();
                    System.out.println("Connecting from local address : "+theConnection.getLocalAddress());
                    System.out.println("Connection request from : "+theConnection.getInetAddress());
                    Thread input=new Thread()
                         public void run()
                              try
                                   //Input starts from here
                                   Reader in=new InputStreamReader(new BufferedInputStream(new CipherInputStream(theConnection.getInputStream(), desDec)),"ASCII");
                                   StringBuffer strbuf=new StringBuffer();
                                   int c;
                                   while (true)
                                        c=in.read();
                                        if(c=='\n'|| c==-1)
                                             break;
                                        strbuf.append((char)c);
                                   String str=strbuf.toString();
                                   System.out.println("Message from Client : "+str);
                              catch(Exception e)
                                   System.out.println("Error caught inside input Thread : "+e);
                    input.start();
                    Thread output=new Thread()
                         public void run()
                              try
                                   //Output starts from here
                                   OutputStream out=new BufferedOutputStream(new CipherOutputStream(theConnection.getOutputStream(), desEnc));
                                   System.out.println("it will not be printed");
                                   out.write("You are Welcome\n".getBytes());
                                   out.flush();
                              catch(Exception e)
                                   System.out.println("Error caught inside output Thread : "+e);
                    output.start();
                    try
                         output.join();
                         input.join();
                    catch(Exception e)
                    theConnection.close();
          catch(BindException e)
               System.out.println("The Port is in use or u have no privilage on this port");
          catch(ConnectException e)
               System.out.println("Connection is refused at remote host because the host is busy or no process is listening on that port");
          catch(IOException e)
               System.out.println("Connection disconnected");
          catch(Exception e)
     public static void main(String args[])
          serverSocketDemo server=new serverSocketDemo();
clientSocketDemo.java
import java.io.*;
import java.net.*;
import java.security.*;
import java.security.spec.*;
import javax.crypto.*;
import javax.crypto.spec.*;
import java.util.*;
import java.util.zip.*;
class clientSocketDemo
     private Cipher desEnc,desDec;
     clientSocketDemo()
          try
               // register the provider that implements the algorithm
               Provider sunJce = new com.sun.crypto.provider.SunJCE( );
               Security.addProvider(sunJce);
               // create a key
               byte[] desKeyData = "This encryption can not be decrypted".getBytes();
               DESKeySpec desKeySpec = new DESKeySpec(desKeyData);
               SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
               SecretKey desKey = keyFactory.generateSecret(desKeySpec);
               desEnc = Cipher.getInstance("DES");
               desDec = Cipher.getInstance("DES");
               desEnc.init(Cipher.ENCRYPT_MODE, desKey);
               desDec.init(Cipher.DECRYPT_MODE, desKey);
          catch (javax.crypto.NoSuchPaddingException e)
               System.out.println(e);
          catch (java.security.NoSuchAlgorithmException e)
               System.out.println(e);
          catch (java.security.InvalidKeyException e)
               System.out.println(e);
          catch(Exception e)
               System.out.println(e);
          startProcess();
     public void startProcess()
          try
               final Socket theConnection=new Socket("localhost",2000);
               System.out.println("Connecting from local address : "+theConnection.getLocalAddress());
               System.out.println("Connecting to : "+theConnection.getInetAddress());
               Thread output=new Thread()
                    public void run()
                         try
                              //Output starts from here
                              OutputStream out=new BufferedOutputStream(new CipherOutputStream(theConnection.getOutputStream(), desEnc));
                              out.write("Please Welcome me\n".getBytes());
                              out.flush();
                         catch(Exception e)
                              System.out.println("Error caught inside output thread : "+e);
               output.start();
               Thread input=new Thread()
                    public void run()
                         try
                              //Input starts from here
                              Reader in=new InputStreamReader(new BufferedInputStream(new CipherInputStream(theConnection.getInputStream(), desDec)),"ASCII");
                              System.out.println("it will not be printed");
                              StringBuffer strbuf=new StringBuffer();
                              int c;
                              while (true)
                                   c=in.read();
                                   if(c=='\n' || c==-1)
                                        break;
                                   strbuf.append((char)c);
                              String str=strbuf.toString();
                              System.out.println("Message from Server : "+str);
                         catch(Exception e)
                              System.out.println("Error caught inside input Thread : "+e);
               input.start();
               try
                    output.join();
                    input.join();
               catch(Exception e)
               theConnection.close();
          catch(BindException e)
               System.out.println("The Port is in use or u have no privilage on this port");
          catch(ConnectException e)
               System.out.println("Connection is refused at remote host because the host is busy or no process is listening on that port");
          catch(IOException e)
               System.out.println("Connection disconnected");
          catch(Exception e)
     public static void main(String args[])
          clientSocketDemo client=new clientSocketDemo();
**** I know that the CInput tries to read some header stuff thats why i used two threads for input and output.
Waiting for the reply.
Thank you.

Do not ever post your code unless requested to. It is very annoying.
Try testing what key is being used. Just to test this out, build a copy of your program and loop the input and outputs together. Have them print the data stream onto the screen or a text file. Compare the 1st Output and the 2nd Output and the 1st Input with the 2nd Input and then do a static test of the chipher with sample data (same data which was outputted), then do another cipher test with the ciphertext created by the first test.
Everything should match - if it does not then follow the steps below.
Case 1: IO Loops do not match
Case 2: IO Loops match, but ciphertext 1st run does not match loop
Case 3: IO Loops match, 1st ciphertext 1st run matches, but 2nd run does not
Case 4: IO Loops match, both chiphertext runs do not match anything
Case 5: Ciphertext runs do not match eachother when decrypted correctly (outside of the test program)
Problems associated with the cases above:
Case 1: Private Key is changing on either side (likely the sender - output channel)
Case 2: Public Key is changing on either side (likely the sender - output channel)
Case 3: Private Key changed on receiver - input channel
Case 4: PKI failure, causing private key and public key mismatch only after a good combination was used
Case 5: Same as Case 4

Are there any tools for data encryption and decryption ?

Hi,
i am using oracle 9i R2, i want encrypt my data. Are there any tools available in market.
Please let me know the ways to do data encryption and decryption.
Thanks in advance
Prasuna.

970489 wrote:
using DBMS_OBFUSCATION_TOOLKIT.Encrypt /DESEncrypt we can't secure our password...So i am looking for an another alternative.As Blue Shadow said, what are you really trying to achieve?
Encrypting a password is itself not secure. Anything that can be encrypted can be decrypted. That is why Oracle itself DOES NOT encrypt passwords.
Surprised??
Here's what Oracle does with passwords, and what others should be doing if they have to store them.
When the password is created, the presented password - clear text - is concatenated with the username. The resulting character string is then passed through a one-way hashing function. It is that hashed value that is stored. Then when a user presents his credentials to log on to the system, the presented credentials are combined and hashed in the same manner as when the password was created, and the resulting hash value compared to the stored value.

Encrypt and decrypt using dbms_crypto.hash

hi to all i am newbie here and i've just want to ask if how can i decrypt the encryted password.
v_pass_string = 'qwerty';
lower(dbms_crypto.hash(to_clob(v_pass_string),3))
The out is: b1b3773a05c0ed0176787a4f1574ff0075f7521e
and i want to output it into original data which is *'qwerty'*
please help...
thanks in advance

You can't.
HASH is not an encryption algorithm, it is a one-way hashing algorithm. HASHed cannot be converted back to the original value. This is one reason they are used for passwords as they offer the best security.
If you want to encrypt and decrypt values you would use the ENCRYPT and DECRYPT functions of the DBMS_CRYPTO package...
http://www.psoug.org/reference/dbms_crypto.html

Encrypting and Decrypting Data(Its Very Urgent, Please Help.)

Hi,
Can anyone tell me some idea in the below mentioned details.
Iam creating a Function for Encrypting and Decrypting Data Values using
DBMS_OBFUSCATION_TOOLKIT with UTL_RAW.CAST_TO_RAW by using
Key Value as normal.
But the problem, is it possible to have the key value more than 8.
Its showing me error when i give the key value less than 8 or more than 8.
Can u tell me why it happens, is that the limit of the key value or is any other way to do that.
Its Very Urgent, Please Help.
Thanks,
Murali.V

Is this what you're looking for?
Usage Notes
If the input data or key given to the DES3DECRYPT procedure is empty, then the procedure raises the error ORA-28231 "Invalid input to Obfuscation toolkit."
If the input data given to the DES3DECRYPT procedure is not a multiple of 8 bytes, the procedure raises the error ORA-28232 "Invalid input size for Obfuscation toolkit." ORA-28233 is NOT applicable for the DES3DECRYPT function.
If the key length is missing or is less than 8 bytes, then the procedure raises the error ORA-28234 "Key length too short." Note that if larger keys are used, extra bytes are ignored. So a 9-byte key will not generate an exception.
C.

How do I protect my FLV files? or How to encrypt and decrypt FLV files using AIR?

Hi,
I am working on an AIR application, which is developed on eLearning concept. The application mainly deals with flv files. The application contains a video player component, which will stream flv files from an Apache Server and played in my application. Here my concern is I would like to protect my flv files some how against users who may stream them from Apache Server and use them without my application.
I thought of with an idea to do it. But I don't know whether it will work or not. So I am requesting for your suggestions and better ways to do this with a sample.
Here is my thought:
I would like to place the encrypted FLV files at Apache Server side [ Need to know how to encrpt the FLV files using Flex]
As my AIR application send a request for a FLV file, the Apache server should send the decryption key and a stream of FLV file.
AIR application should take the decryption key, stream of flv file and it should capable enough to decrypt the FLV file and play it in my application. [ But I don't know how to encrypt/decrypt FLV files through flex]
I can do encryption of FLV files using Mac Address of Apache Server system and using Java. But I don't know how can I decrypt the same FLV file ( Encrypted using Mac Address and java ) at AIR application side.
So I would be greatfull If any body help me in encrypting and decrypting of FLV file with a sample using Flex 3.0.
Thanks
Sudheer Puppala

russellfromblackburn south wrote:
Is it because the portable drive is NTFS format and the Mac wont recognise this? If so what do I do?
Yes, this is exactly what is causing the problem. Macs cannot write to NTFS formatted drives, only read. You must move the documents to the internal HDD/SSD of the Mac to be able to edit them.
Or, since you say you don't want to move the documents to the internal storage, you'll need to format the external HDD as FAT32.

AES encrypt and decrypt not the same

I use aes to encrypt and decrypt a file. Why is the resulting file not the same as the input?
package mybeans;
import java.io.*;
import java.sql.Blob;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Hashtable;
import javax.crypto.*;
import javax.crypto.spec.*;
public class Encrypt {
     public static void main(String args[]) throws Exception {
          Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
          SecretKeySpec keySpec = new SecretKeySpec(
                    "05468345670abcde".getBytes(), "AES");
          IvParameterSpec ivSpec = new IvParameterSpec("f45gt7g83sd56210"
                    .getBytes());
          cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivSpec);
          FileInputStream fis = new FileInputStream(new File("C:\\text.txt"));
          CipherInputStream cis = new CipherInputStream(fis, cipher);
          FileOutputStream fos = new FileOutputStream(new File(
                    "C:\\encrypted.txt"));
          byte[] b = new byte[8];
          int i;
          while ((i = cis.read(b)) != -1) {
               fos.write(b, 0, i);
          fos.flush();
          fos.close();
package mybeans;
import java.io.*;
import javax.crypto.*;
import javax.crypto.spec.*;
public class Decrypt {
     public static void main(String args[]) throws Exception {
          Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
          SecretKeySpec keySpec = new SecretKeySpec(
                    "05468345670abcde".getBytes(), "AES");
          IvParameterSpec ivSpec = new IvParameterSpec("f45gt7g83sd56210"
                    .getBytes());
          cipher.init(Cipher.DECRYPT_MODE, keySpec, ivSpec);
          FileInputStream fis = new FileInputStream(new File("C:\\encrypted.txt"));
          CipherInputStream cis = new CipherInputStream(fis, cipher);
          FileOutputStream fos = new FileOutputStream(new File(
                    "C:\\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();
}Here is the data in the file:
James,"smith",007
mike,"smith",001
the result is this:
James,"smith",007
mike,"smith",
Edited by: iketurna on Jun 3, 2008 1:47 PM

Thanks sabre!
Very insightful.
I used PKCS5Padding and the file has all of the data, but there are extra padding at the end of the second line
Also,
how would you store your key and iv?
Currently I using this to create the iv and key:
public class KeyClass {
private SecretKeySpec keygeneration() {
SecretKeySpec skeySpec=null;
try {
KeyGenerator kgen = KeyGenerator.getInstance("AES");
kgen.init(128);
SecretKey skey = kgen.generateKey();
byte[] key = skey.getEncoded();
skeySpec = new SecretKeySpec(key,"AES");
}catch(Exception e) {
System.out.println("error in keygen = "+e);
return skeySpec;
public void keyFile() {
try{
FileOutputStream fos=new FileOutputStream("c:\\keyFile.txt");
DataOutputStream dos=new DataOutputStream(fos);
SecretKeySpec skeySpec=keygeneration();
byte[] key=skeySpec.getEncoded();
BASE64Encoder base64 = new BASE64Encoder();
String encodedString = base64.encodeBuffer(key);
dos.write(encodedString.getBytes());
}catch(Exception e1){
System.out.println("error file write "+e1);
public static void main(String args[]){
KeyClass cKey = new KeyClass();
cKey.keyFile();
}Edited by: iketurna on Jun 5, 2008 7:29 AM

The Encrypt and Decrypt functions.

All,
I need to use the Encrypt and Decrypt functions for our password filed in a table.
The procedures need to pass in an input_string (string to be en/decrypted) and a key_string (en/decryption key string). What is the key_string? Where can I get it from? or How can I generate it?
Could someone please give some examples on how to use those functions?
Thanks in advance!

This may help you, works with 8.1.7 upwards :
We used this approach when I worked on a project in Holland. We encrypted customers' names and addresses. Note : the value to be encrypted had to be a multiple of 8 characters in length so we always rpad'd values upto a multiple of 8 say 32 and rtrim'd following decryption. W were using 8.1.7. at the time and I am unsure if this requirement still exists. Note : the encryption key was actually held in a package which was wrapped and in a schema with password only known to few.
set serverout on size 1000000
declare
   input_string_c     varchar2(16) := '1234567812345678'; -- must be multiple of 8 bytes long
   key_string_c       varchar2(57) := 'abcdefghijklmnop'; -- the key needs to be at leat 8 bytes long
   encrypted_string_c varchar2(2048);
   decrypted_string_c varchar2(2048);
begin
   dbms_obfuscation_toolkit.desencrypt (input_string     => input_string_c,
                                        key_string       => key_string_c,
                                        encrypted_string => encrypted_string_c) ;
   dbms_obfuscation_toolkit.desdecrypt (input_string     => encrypted_string_c,
                                     key_string       => key_string_c,
                               decrypted_string => decrypted_string_c);
   dbms_output.put_line('encrypted string = >'||encrypted_string_c||'<');
   dbms_output.put_line('decrypted string = >'||decrypted_string_c||'<');
end;
/HTH
AMM

Question regarding encryption and decryption

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