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Let’s say I want to find a partial rather than full preimage using the meet-in-the-middle attack. For example, my goal is to find a preimage so that the first 76-bit output of the hash are all consisted of the number 1.

Does finding a partial preimage have a better chance of success than finding a full preimage using the meet-in-the-middle attack? If so, what is the complexity of this attack?

EDIT: I know that there is no full-round meet-in-the-middle attack against SHA256 to find full preimages. However, my question is: would it be easier to execute a full-round meet-in-the-middle attack to find a partial preimage instead?

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    $\begingroup$ Note that there is no full round meet-in-the-middle attack on SHA256. $\endgroup$
    – kelalaka
    Mar 7 '20 at 16:54
  • $\begingroup$ @kelalaka I know that there is no full round meet-in-the-middle attack against SHA256 to find a full preimage. However, would it be easier to accomplish a full round meet-in-the-middle attack to find a partial preimage instead? $\endgroup$ Mar 8 '20 at 2:06
  • $\begingroup$ I'm pretty sure that the researchers would go in this way if they saw that there is a better result than the existing one. $\endgroup$
    – kelalaka
    Mar 8 '20 at 9:22

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