Re: Triple DES Perl to Java

"Mr. Skeptic" <>
23 Aug 2006 18:06:37 -0700
Alex wrote:

Alex wrote:


I am having a base64 encoded data block, which has been triple des
encrypted with Perl's Crypt::TripleDES class
( and
am trying to decrypt it with Java.

My problem is now that whatever I already tried I always get some
exception with messages from a wrong padding to nonexistent algorithms.
Below is some sample code with "O2OsvkIsfY0=" as base64 encoded data
block (decoded "data") and "key" as encryption key.

I just noticed that PBE is apparently not the right algorithm and by
using the following code I at least dont get exceptions anymore, but the
output is not the expected one.


   import javax.crypto.*;
   import javax.crypto.spec.*;
   import sun.misc.BASE64Decoder;

   public class Test
       public static void main(String args[]) throws Exception
           String data="O2OsvkIsfY0=";
           String key="key ";

           byte b_data[]=new BASE64Decoder().decodeBuffer(data);

           SecretKeyFactory skf=SecretKeyFactory.getInstance("DESEDE");

           DESedeKeySpec dks=new DESedeKeySpec(key.getBytes());

           SecretKey sk=skf.generateSecret(dks);

           Cipher cipher=Cipher.getInstance("DESEDE/ECB/NOPADDING");
           cipher.init(Cipher.DECRYPT_MODE, sk);
           System.out.println(new String(cipher.doFinal(b_data)));

Does somebody know where I am wrong? Thanks.

Looks pretty good. One likely problem is that the perl module processes
the key slightly differently. I'm not really a perl expert, but it
looks like perl treats the $passphrase argument as a 48-byte hex-ASCII
encoded key. As an added twist, the perl pack function will just use
the last four bits of the ASCII code for non-hex characters, i.e. if
the letter 'k' is put in $passphrase it will be treated as if it was
the hex character 'b'.

For example; your java key is the 24 byte array new byte [] { 'k', 'e',
'y', ' ', ..., ' '}; To get the same key in perl you set $passphrase to
'6a6579202020...' on out to 48 characters. Conversely, if in perl you
set $passphrase to 'key', the equivalent java key is the 24-byte array
new byte[] {0xb5, 0x90, 0x0, ..., 0x0}.

Another nit is the use of String.getBytes() without specifying an
explicit encoding, and similarly the use of the String constructor
without specifying an encoding.

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