Hi, first if you use dmcrypt or any other disk encryption the data you write to the disk is encrypted. This also means that empty disk space does not contain crypto data which tells an attacker at least how much disk space on your crypto disk is used and, most important, he can also identify the ciphertext "blocks" and eventually mount e.g. statistical attacks on them. Anothing thing is that why a perfect encryption algorithm should have it's output equally distributed there are some deviations from that with some real life applications (especially the chaining modes can be dangerous). Have a look at the different cipher block chaining modes, the wikipedia article also contains an example of non equally distributed ciphertext in the now possibly obsolete ECB chaining mode. http://en.wikipedia.org/wiki/Cipher_block_chaining Now, if you fill up wour disk with good random data, it will be very hard to identify the ciphertext blocks since they look like random data. Thus the attacker does not even know the ciphertext ;) greets, stefan On Thu, 22 Feb 2007 12:55:09 +0000 (UTC) Michael Schmidt <drmike@xxxxxxx> wrote: > Hi, > > the on-line LUKS documentation recommends for crypto-analytic reasons to > initialize any partition that is to becom encrypted by LUKS to be initialized > with random data (from: http://www.saout.de/tikiwiki/tiki-index.php? > page=EncryptedDeviceUsingLUKS): > > Note : if you want your encryption to defeat a full cryptoanalytic attack, not > just casual snooping, you need to fill the disk with high quality random data. > Badblocks below justs uses 'libc' random(), but is fast (your limitation will > be disk speed, not CPU speed). /dev/urandom is better (takes about 5 minutes > per gigabyte on my system), /dev/random is best (takes about 1 year per > gigabyte on my system, much too slow!). > > > What's the very reason for it (besides eliminating any left-over plaintext > data)? Is there any scientific papaer or reference backing this up? > > > Thanks in advance, > > Michael > --------------------------------------------------------------------- dm-crypt mailing list - http://www.saout.de/misc/dm-crypt/ To unsubscribe, e-mail: dm-crypt-unsubscribe@xxxxxxxx For additional commands, e-mail: dm-crypt-help@xxxxxxxx
