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Let's suppose I want to encrypt my disk partition with AES-256 in CTR mode 2 times using two different keys and IVs.

Will I get 512 bits of encryption strength?

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  • $\begingroup$ You are correct, the 1D-meet-in-the-middle attack applies. If you have four or more matched plain and cipher blocks, you have a good chance of uniquely identifying the key without additional testing. Thus the overall complexity will be a little over 256-bits. Note that the memory requirements are much bigger than for exhaustive attacks. $\endgroup$ – Daniel Shiu Apr 16 at 6:23
  • $\begingroup$ Why do you need 512-bit encryption? $\endgroup$ – kelalaka Apr 18 at 17:48
  • $\begingroup$ @kelalaka -- I'm too paranoid and I want to keep my encryption safe against quantum computers. $\endgroup$ – phantomcraft Apr 20 at 0:21
  • $\begingroup$ Use 256-bit key size then you are safe : Has AES-128 been fully broken? $\endgroup$ – kelalaka Apr 20 at 0:23

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