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5

XTS is designed so that the plaintext and ciphertext sizes are the same. This is "needed" for disk encryption in order to preserve the sector size. However, when you are encrypting your disk at the file level, this is a completely irrelevant issue. Also, XTS is not "ideal" in the sense that it's not truly a wide block cipher (defined as a pseudorandom ...


4

It depends. (Usual answer to this kind of questions. We would need more details about the data damage to answer) XTS encryption mode is short for XEX-based tweaked-codebook mode with ciphertext stealing, and XEX stands for Xor-encrypt-xor. Let's look how the XEX mode is defined: (image from wikipedia) XTS definition changes only how the last block is ...


4

Use XTS for whole-disk encryption. It is designed for that purpose. Definition of XTS mode in wiki is under the Disk Encryption Theory which says enough i think :) In GCM, for a fixed key each, IV value must be distinct. This makes it disadvantageous for encryption of large files. From an early GCM question: GCM is bounded to encrypting about 68 GB ...


3

From what I understood, data units are sectors, so a sector can have at most $2^{128}-2$ blocks but you can only encrypt $2^{20}$ blocks which cannot be correct (it seems too little compared to a disk's capacity). The data unit is the sector, yes, but both of those quotes only talk about the length of a single data unit. The larger number in the latter ...



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