On Qui, 27 Jan 2011, Celejar wrote:
Now another question, which nobody seems to have noticed/mentioned.
Since CBC encryption is a "recursive algorithm, the encryption of the n-th
block requires the encryption of all preceding blocks, 0 till n-1." [1]
Now, does it mean if my HD has a bad block in the middle, then all the
remaining data will be gone entirely?
1. http://clemens.endorphin.org/LinuxHDEncSettings
This seems correct - Wikipedia also says that with CBC:
"Note that a one-bit change in a plaintext affects all following
ciphertext blocks."
http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation#Cipher-block_chaining_.28CBC.29
That is correct, but the whole disk is not one single CBC-encoded
unity. The link in the question message says that:
[...] CBC chaining is cut every sector and restarted with a new
initialisation vector (IV), so we can encrypt sectors individually.
The choice of the sector as smallest unit matches with the smallest
unit of hard disks, where a sector is also atomic in terms of access.
http://clemens.endorphin.org/LinuxHDEncSettings
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