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List:       bouncycastle-crypto-dev
Subject:    Re: [dev-crypto] java.lang.IllegalArgumentException: no IV set
From:       David Hook <dgh () bund ! com ! au>
Date:       2007-06-18 10:14:46
Message-ID: 1182161686.3408.89.camel () echidna
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CFB mode requires an initialisation vector (IV) and you'll need to make
sure it is the same for decryption as it is for encryption. In the
example below c1.getIV() will return the IV the cipher generated.

You'll probably find that the system you are dealing with uses one with
every byte set to zero, but you might not.

Regards,

David

On Mon, 2007-06-18 at 14:58 +0530, Sreelatha Kancherla wrote:
> 
> Hi , 
> 
> I have to encrypt a string in AES algorithm in CFB or OFB mode. I have
> no option to change the mode or algorithm as this needs to be
> compatible with another existing system. I have to decrypt it back at
> later point to get the original string. I am using BC provider. 
> 
> Below is my piece of code to do the same: 
> 
> Encryption logic: 
> Cipher c1 = Cipher.getInstance("AES/CFB/NOPADDING", "BC"); 
> SecretKeySpec sk = new SecretKeySpec("1234567890123456".getBytes(),
> "AES"); 
> c1.init(1, sk); 
> byte[] encrBlock =
> c1.doFinal("94579012345084623451".getBytes("UTF8")); 
> 
> Decryption logic: 
> Cipher c2 = Cipher.getInstance("AES/CFB/NOPADDING", "BC"); 
> SecretKeySpec sk = new SecretKeySpec("1234567890123456".getBytes(),
> "AES"); 
> c2.init(2, sk); 
> byte[] decrBlock = c2.doFinal(encrBlock); 
> 
> Encryption is happening properly. But while executing decryption
> logic(more precisely, at c2.init()), it is throwing the following
> exception.  
> 
> java.lang.IllegalArgumentException: no IV set when one expected 
>         at
> org.bouncycastle.jce.provider.JCEBlockCipher.engineInit(JCEBlockCipher.java:482) 
>         at javax.crypto.Cipher.init(DashoA6275) 
> 
> 
> Does anyone there know what's the problem here?? What is this IV it's
> talking about?? 
> 
> Thanks in Advance. 
> 
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