Complex sentence: For this timing attack to work, Cipher block chaining (CBC) must be used-in this mode, if a block's bit is inverted, the following block, when deciphered, will contain that same bit inversion.
Split into simpler sentences: For this timing attack to work, cipher block chaining (CBC) must be used. In this mode, if a block's bit is inverted, the following block, when deciphered, will contain that same bit inversion.