FISH v0.97a for xchat ********************* This is an encryption plugin for xchat, it is based on blowfish and is fully compatible to original 'blowcrypt' script. It supports private chat and channel encryption. A secure key-exchange system is included aswell. Please read the whole document, especially the 'Installation' section, before installing it! FiSH v0.97 has been tested with xchat for windows v2.0.8b and xchat for linux v2.0.6 ============== FiSH commands: ============== - /key [] Show key for target. If no target specified, the key for current window will be shown. - /setkey [] Set key for target to sekure_key. If no target specified, the key for current window will be set to sekure_key. - /delkey Delete key for target. You have to specify the target. - /keyx [] Perform DH1080 KeyXchange with target. If no target specified, the KeyXchange takes place with the current query window. - /msg+ Send encrypted message to nick/channel. You have to specify the target. - /notice+ Send encrypted notice message to nick/channel. You have to specify the target. - /topic+ Set encrypted topic for current channel. Keep in mind: topic size SHRINKS drastically to about 60%! This is already insufficient for a common eBay URL - /setinipw Set a custom password to encrypt your key-container (blow.ini) - you will be forced to enter it each time you load the module. If you do not set a custom blow.ini password, a default password will be used. *insecure* *NOTE* Take care of all your keys when using this feature, they should get re-encrypted when changing the blow.ini password, but nothing is guaranteed :) - /unsetinipw Change back to default blow.ini password - /fishpw (linux version only) in case you have a custom blow.ini password you could use this command to set it after FiSH is loaded, it is also possible to load FiSH using: /load /path/xfish.so ============= Installation: ============= - copy xfish.so to xchat's home directory, usually it will be loaded on xchat startup. If not, you could also use: /load /path/to/xfish.so - xchat for windows expects the plugins in \xchat\plugins, place xFiSH.dll there - in case you have a custom blow.ini password you could also use following command to load FiSH: /load /path/xfish.so (linux version only) - blow.ini should be located in your xchat home directory - Blow.ini options explained: --------------------------- [FiSH] process_incoming=1 --> decrypt incoming messages? process_outgoing=1 --> encrypt outgoing messages? plain_prefix="+p " --> messages starting with +p will be sent plain-text [incoming_format] crypted_privmsg="15<%s15> %s" crypted_chanmsg="15<%s15> %s" [outgoing_format] crypted_privmsg="15<%s15> %s" crypted_chanmsg="15<%s15> %s" ------------------- - Set mark_broken_block=0 (in blow.ini) if you want to disable the "mark broken block" feature, which indicates whether a broken block was cut, meaning the message arrived incomplete (enabled by default) - you could change the nick format by editing the entries mentioned above. hint: paste the lines in your IRC client to see how the format would look like (you can use usual IRC color codes) - 'NickTracker' allows seamless conversations in the case your chat partner suddenly changes his nick. This feature will simply copy the old key to use with his new nick. It affects nick changes for running queries only! (enabled by default, to disable set nicktracker=0 in blow.ini) ============== Security Info: ============== What happened to DH1024 key-exchange you may ask. To make it short: An implementation flaw in the code has been found and a new key-exchange using Diffie-Hellman 1080 bit has been introduced. The implementation flaw is NOT about a remote vulnerability, it is rather about maths :) The analysis of a friend has come to the conclusion: The old DH1024 key-exchange was probably still as secure as 991 bit. We cannot say for sure. The characteristic of the implementation flaw makes it hard to analyze, as not many material about this subject is available. I was very angry when this problem was discovered, but I can't change what happened now. Such a stupid mistake, unnoticed almost a year. Well, everyone learns from mistakes ... Make sure you NEVER exchange keys plain-text over IRC/ftp/email! If you ever do that, or someone else who owns that key, you can also just keep talking plain-text. Use the new Diffie-Hellman (1080 bit) keyXchange function! You might think this is crazy, but keep in mind: You are using IRC encryption because you think someone might be able to read your conversations. Such a person may not only have enough skills for that, but also for defeating your weak encryption mechanism, including passwords sent in plain-text and maybe even using DH-128. While rewriting the Diffie-Hellman key-exchange, it was discovered that the used 128bit numbers in DH.dll (written by sinner?) are far not enough for secure key-exchange! It would take just approx. 3 hours to calculate someones private key by having only the transmitted public key, on a 1.7 GHz machine with 256 MB RAM! Now half of the time is used for pre-computation, which needs to be done only once. And from that point you can calculate any private key generated with the DH.dll in only 1.5 hours! This applies to *all* DH key-exchange plug-ins using 128bit keys! It is suggested to use at least 512bit for Diffie-Hellman. Therefore keyXchange with Diffie-Hellman in this addon was upgraded to 1080bit. It is not compatible to the old DH keyXchange with 128bit! The DH routines have been completly rewritten using MIRACL. (Thanx to mac for discovering the weakness of DH128 and helping me!) ================ Technical notes: ================ For Diffie-Hellman key-exchange a 1080bit germain prime is used, the generator g=2 renders a field Fp from 1 to p-1. Therefore breaking it means to solve a discrete logarithm problem with no less than 1080bit. Base64 format is used to send the public keys over IRC. The calculated secret key is hashed with SHA-256, the result is converted to base64 for final use with blowfish. ========== TODO List: ========== - slap xchat development and make them fix the 'umlaut' problem (guys, please create a pre-process hook for outgoing messages... so that you can encrypt the message/notice/topic before the font encoding or whatever screws up the umlaute etc.) Comments and suggestions are welcome! Enjoy 27. July 2004 FiSH URL: http://fish.sekure.us/