encryption decryption

[rajendra peddinti]

when i tried to execute the following code:

  import java.security.*;
import javax.crypto.*;
// Public Key cryptography using the RSA algorithm.
public class PublicExample 
{
public static void main (String[] args) throws Exception {
// check args and get plaintext
if (args.length !=1) 
{
 
System.err.println("Usage: java PublicExample text");
 
System.exit(1);
 
}
 
byte[] plainText = args[0].getBytes("UTF8");
 
//
 
// generate an RSA key
 
System.out.println( "\nStart generating RSA key" );
 
KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA");
 
keyGen.initialize(1024);
 
KeyPair key = keyGen.generateKeyPair();
 
System.out.println( "Finish generating RSA key" );
 
//
 
// get an RSA cipher object and print the provider 
 
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS5Padding");
 
System.out.println( "\n" + cipher.getProvider().getInfo() );
 
//
 
// encrypt the plaintext using the public key
 
System.out.println( "\nStart encryption" );
 
cipher.init(Cipher.ENCRYPT_MODE, key.getPublic());
 
byte[] cipherText = cipher.doFinal(plainText);
 
System.out.println( "Finish encryption: " );
 
System.out.println( new String(cipherText, "UTF8") );
 
//
 
// decrypt the ciphertext using the private key
 
System.out.println( "\nStart decryption" );
 
cipher.init(Cipher.DECRYPT_MODE, key.getPrivate());
 
byte[] newPlainText = cipher.doFinal(cipherText);
 
System.out.println( "Finish decryption: " );
 
System.out.println( new String(newPlainText, "UTF8") );
 
}
 
}
 
 
 
 
  

i am getting error like,

Cannot find any provider supporting RSA/ECB/PKCS5Padding
at javax.crypto.Cipher.getInstance(DashoA12275)


i am using java 1.4.2 api. do my api missing this rsa/ecb/pkcs5padding algorithm module or what??

[Ulf Dittmer]

Welcome to JavaRanch.

According to this, "ECB" is defined in a document called "DES Modes of Operation", which suggests to me that it may be applicable to DES, and not necessarily to RSA. Have you tried a different mode?

[rajendra peddinti]

yeah i've tried they re working fine. but my objective is to do on "RSA". can't we do that using java api?

[Ulf Dittmer]

My point was that ECB may not work with RSA, and that you should try a different mode (e.g. NONE), not a different cipher.

Also, this will not work:

System.out.println( new String(cipherText, "UTF8") );

Cipher text is binary, not text, so you can't convert it to a String like this. If you need an ASCII representation of it, use base-64 encoding.

[rajendra peddinti]

Ulf!
thanks for the reply. but its not problem with mode. the algorithm it self is not geting recognised.
when i debug.

  catch(NoSuchAlgorithmException e){
   System.out.println("No such Algothm" +
   "");
}  

it is catching. why their is no algorithm? is that problem with my api. i tried to get jce.jar but couldn't make it out.

[Ulf Dittmer]

What JCE calls algorithm is the combination of cipher, mode and padding. Have you tried using NONE instead of ECB for the mode?

[rajendra peddinti]

you mean "cipher is a comibanation of algorithm,mode and padding" ?...yes, i tried NONE as mode and find no change in result.

[Ulf Dittmer]

Originally posted by rajendra peddinti:
you mean "cipher is a comibanation of algorithm,mode and padding" ?

No, I meant what I wrote. The point is that what JCE calls algorithm is not something like RSA or DES (which it calls cipher), but the combination of that with the mode and the padding. Any introduction to JCE will explain this in detail.

[rajendra peddinti]

but in the link provided by you(in the your first reply of this thread)..it was like under Cipher their are three parts algorithm,mode,padding and under algorithm the rsa/des etc. were specified. i got less idea on jce.jar anyways. but what do you think is the problem with my code?

[rajendra peddinti]

more over instead of

 Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS5Padding");   

when i use

  Cipher cipher = Cipher.getInstance("RSA");  

i.e. no mode and no padding, even then i am getting the same error. so if i'm not wrong,error has got nothing to do with "ECB" , the Mode. what do you say??

[Jeremy Botha]

Has it occured to you that NoSuchAlgorithmException is probably thrown because the cipher engine cannot find the specified algorithm/mode/padding combination you're specifying?

Print out a list of your cipher engine's supported algorithms and modes and I'm pretty sure you will not find RSA/ECB anywhere in the list.

J

[rajendra peddinti]

jeremy

let us assume what you said that is, error is coming because of "wrong combination", is right. but i've tried

Cipher.getInstance("RSA")

(that is no mode and padding) which even returned the same error(refer my last post). what do you think is the acual problem?

[rajendra peddinti]

guys,

i just found in IBM tutorial that

RSA algorithm won't work in java1.4 and we should use a third party tool like bouncycastle.

anyways thanks for your concern.