On Fri, Jun 17, 2005 at 12:59:14PM -0700, Ben Pfaff wrote: > martin f krafft <[EMAIL PROTECTED]> writes: > > > However, doesn't CBC or EBC make sure that every block is > > chained to its predecessor, making even the very last block of > > a file dependent on the bits of the very first block? > > Yes and no. If you change the first block in a set of > CBC-chained blocks, the last block will change. But to recover > the contents of the last block, you only need the last block and > the preceding block (and the key).
A good explanation of this mode (dubbed "Sector Enciphering Operation") is in Saarinen's paper about the watermark weakness[1]. cryptoloop and siblings basically use CBC only within a sector (512 byte), so different sectors are all independent from each other. cheers, Max [1] http://docs.indymedia.org/twiki/pub/Local/UkCrypto/wisa2004.pdf -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
