Decrypting with Cipher

Hi

I have a client that encrypts a message and sends it to the server.  I
can encrypt fine:
byte[] dataToSend = new byte[somelength];

/*fill dataToSend with some data*/

Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.ENCRYPT_MODE,  serverPubKey);     	     byte[]
ciphertext = cipher.doFinal(dataToSend);

However, when I try to decrypt on the server side with:


Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.DECRYPT_MODE,  serverPrivateKey);
byte[] dataReceived = cipher.doFinal(data);

The output alternates (most of the time is 1 but some times is 2)
between follong errors:

1.  javax.crypto.BadPaddingException:  Data must start with
zero
2.  javax.crypto.BadPaddingException:  Message is larger than
modulus.


Does anyone have any idea how I can fix this?

try

Cipher.getInstance("RSA/ECB/PKCS1Padding");

on both sides.

Karl

--

Karl Scheibelhofer, IAIK - Graz University of Technology
Inffeldgasse 16a, 8010 Graz, Austria
Fax: +43 316 873 5520
http://jce.iaik.tugraz.at/



<gtornelas@utep.edu> wrote in message
news:1112934343.746065.8600@z14g2000cwz.googlegroups.com...
> Hi
>
> I have a client that encrypts a message and sends it to the server.  I
> can encrypt fine:
>              byte[] dataToSend = new byte[somelength];
>
>              /*fill dataToSend with some data*/
>
>              Cipher cipher = Cipher.getInstance("RSA");
>      cipher.init(Cipher.ENCRYPT_MODE,  serverPubKey);          byte[]
> ciphertext = cipher.doFinal(dataToSend);
>
> However, when I try to decrypt on the server side with:
>
>
>          Cipher cipher = Cipher.getInstance("RSA");
> cipher.init(Cipher.DECRYPT_MODE,  serverPrivateKey);
> byte[] dataReceived = cipher.doFinal(data);
>
> The output alternates (most of the time is 1 but some times is 2)
> between follong errors:
>
>           1.  javax.crypto.BadPaddingException:  Data must start with
> zero
>           2.  javax.crypto.BadPaddingException:  Message is larger than
> modulus.
>
>
> Does anyone have any idea how I can fix this?
>

Hi all,
    I also have the same problem. 

Error as follows:
  Exception in thread "main" javax.crypto.BadPaddingException: Data must sta
rt with zero
 
 I tried using 
Cipher.getInstance("RSA/ECB/PKCS1Padding");.
But it is showing the same error.

Thanks in advance for any suggestions.