John Kennedy wrote: > <snip> > At what point is someone going to get burned? I started out looking > into it as a security and anti-tampering system -- even if someone did > have physical possession or access to the hardware, it wouldn't do them > a lot of good without a LOT (hopefully horribly prohibitive) of work. > How many bits do I have to give them before my effort is all for naught? <snip> In short: None. Long version: That is because you make the common mistake of Q> encryption == integrety. That is not so! The right equality is: Q> encryption == confidelity. You said, you wanted security and tamper-proofness. You got nothing of that, since anyone could substitute blocks. If you want a system that is tamper-proof, start by installing tripwire on that floppy disk and run it daily (YMMV). It is of course right that given an encrypted disk it is computationally infeasible (at least to the extent known to the public) to make a _subtle_ change. Poking around encrypted blocks and changing some of them will in general yield garbage. But the point is that, given that garbage, you cannot deduce from that whether the ciphertext has been tampered with or the garbage was there before encryption took place. So, I _guess_ that you want not only integrety-checking, but also confidelity. Serpent-encryption will buy you that. It is probably the most secure cipher known to the public at this point. But if you want integrety, then you should additionally install tripwire, read the Security-HOWTO and B. Schneier's Applied Cryptography. Marc -- Marc Mutz <Marc@xxxxxxxx> http://EncryptionHOWTO.sourceforge.net/ University of Bielefeld, Dep. of Mathematics / Dep. of Physics PGP-keyID's: 0xd46ce9ab (RSA), 0x7ae55b9e (DSS/DH) Linux-crypto: cryptography in and on the Linux system Archive: http://mail.nl.linux.org/linux-crypto/
