Cryptography Stack Exchange
Cryptography Stack Exchange

Questions tagged [xts]

XTS is a block cipher mode of operation, which is most commonly used when random accessible data (like a hard disk or RAM) is to be encoded.

XTS is a block cipher mode of operation, which is most commonly used when random accessible data (like a hard disk or RAM) is to be encoded.

In January 2010, XTS-AES was added by NIST in SP800-38E: "Recommendation for Block Cipher Modes of Operation: The XTS-AES Mode for Confidentiality on Storage Devices."

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XTS mode with the tweak key as the sole secret

The keyspace of XTS is $2^{512}$ due to its use of two distinct keys, and the most effective attack (a meet-in-the-middle attack) brings this down to $2^{384}$. This implies that knowledge of either the main key or the tweak key does not…
forest
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What is the benefit of applying the tweak a second time using XTS?

I tried to understand the inner working of XTS. What I understood is that it is applying the tweak two times: once on the plaintext and once on the output. What is the benefit of applying the tweak on the cipher text also?
Tamas
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