I have read an article about an attack on LUKS in CBC mode and had a look at the
ID: 652965 • Letter: I
Question
I have read an article about an attack on LUKS in CBC mode and had a look at the WP article about CBC and now I am confused. If I have understood that correctly then changing the plaintext of a block affects all following blocks because every block needs the ciphertext of the previous block to be decrypted. Changing the plaintext (i) changes the ciphertext so (in my understanding) you have to rewrite the next block (i+1) so that the changed ciphertext of i still leads to the correct plaintext of i+1. Rewriting i+1 causes the same problem for i+2.
This doesn't make sense so obviously I misunderstand something important.
Explanation / Answer
In short: for disk encryption, data is organized in sectors (for instance of size 512 bytes), and data may be encrypted with a chaining mode of operation such as CBC only inside these sectors, using a different initialization vector for each sector.