On Mon, Oct 02, 2006 at 03:16:31PM +1300, Richard Dingwall wrote:
> Hi,
>
> I'm trying to decrypt messages that are encrypted with Eggdrop's
> blowfish encrypt() method. This method is also used by a
> irssi/mirc/xchat encryption module called FiSH.
>
> I have already written some code to do it using libcrypto's EVP, but
> it produces gibberish output. You can see it here:
>
> http://rafb.net/paste/results/e15Deu53.html
>


Your paste does not exist.

> (ignore the == key.length(); on EVP_BytesToKey, it was part of an
> assertion I forgot to remove).
>
> I have two questions.
>
> Firstly, I understand the eggdrop's blowfish stuff uses a custom
> base64 method. The differences from 'standard base64' RFC 2045
> (inherits RFC 1421) include:
>
> * The character assignments are different ("./0-9a-zA-Z" instead of
> "A-Za-z0-9+/")
> * Encoding is done low-order to high-order in 32bit blocks, instead of
> high-order to low-order in 24bit blocks. This leaves leftovers.
> * No support for padding character (=)
>
> How might I use libcrypto to solve my problem?
>


You can't. Either copy the required code from eggdrop's code (if
permitted) or write your own.

> Secondly, it uses ECB mode, and apparently ECB mode doesn't use an IV.
> Am I initializing the key correctly?


Actually unless I am mistaken, eggdrop uses hacked mode (yack).

From source:
/* Robey: Reset blowfish boxes to initial state
* (I guess normally it just keeps scrambling them, but here it's
* important to get the same encrypted result each time)
*/

Thus I am not convinced at all that this is even possible.

Aki Tuomi


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