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Modern hardware and software disk encryption uses AES mode of operation. But XTS was designed to "pad" the last block when the disk sector was not divisible by block size.

However all typical disk sector sizes are divisible by AES block size (128bit). So does that mean that disk encryption uses XEX mode and not doing cipher-text stealing at all?

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However all typical disk sector sizes are divisible by AES block size (128bit). So does that mean that disk encryption uses XEX mode and not doing cipher-text stealing at all?

Given that XTS is indistinguishable from XEX if the block size divides the sector size, yes disk encryption in practice nearly always uses XEX / XTS. While in theory you could now go on and always call it "XEX" in practice I'd recommend against it given that more people will recognize "XTS" than "XEX".

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    $\begingroup$ Also, XTS mode includes a tweak value derivation function for each sector and ciphertext block (respectively). Plain XEX mode does not include that and would otherwise behave like ECB mode. $\endgroup$ – Natanael Sep 30 at 6:10

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