Am Mo, den 13.10.2003 schrieb Joe Thornber um 14:23: > > Maybe, i'm not a cryptoanalyser, but GBDE does this, and i think they > > do it for a reason. The idea is that you can attack the encryption if > > you have "known plaintext", and a filesystem stores known meta data > > at a known location. > > y, I can see that making a difference for some encryption schemes. > Perhaps we should think about putting that in. Knowing things about the underlying structure of the filesystem or encryption scheme makes it easier for attacks. You've simply got a lot of data to analyse and if you know in which order it's put on the disk it makes this a lot easier. GBDE also changes the encryption key every nth sector. The IV (the additional "per-sector-perturbation data") isn't predictible either. Some keys are spread all over the volume in special sectors so that you first have to know how to decode these before you can begin making assumptions about the actual encrypted data. Because you don't know where these sectors are without having the master key it makes the kind of attacks stated above nearly impossible. -- Christophe Saout <christophe@xxxxxxxx> Please avoid sending me Word or PowerPoint attachments. See http://www.fsf.org/philosophy/no-word-attachments.html