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If a password p is selected from a space of 2^64 passwords, and the server stores this as a hash, h = SHA-256(p||s) where s is a random 128-bit salt. How many maximum hashes would an attacker need to perform to recover "p" given (h,s)?

I was thinking that this is a pre-image attack so the attacker needs to find the same hash as the passwords. SHA-256 provides 256 bits of pre-image resistance. So I was thinking the attacker would need in the worst case 2^256 hashes to recover "p".

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    $\begingroup$ This is not a collision attack, since the attacker is not allowed to freely choose the two colliding outputs. Instead, there a strategy that always finishes with at least one guess $\endgroup$
    – Marc Ilunga
    Nov 17, 2022 at 0:06
  • $\begingroup$ Consider 1) what is the answer if there is no salt and 2) how does adding salt change the answer? $\endgroup$
    – bmm6o
    Nov 17, 2022 at 0:56
  • $\begingroup$ Oh, so it's actually a pre-image attack. $\endgroup$
    – CryptoGuru
    Nov 17, 2022 at 3:11
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    $\begingroup$ This is closed as homework. It's an easy one. Hint: often the best strategy to find a password (password cracking) is to try all passwords (in practice, about from most to least common, but that refinement is not in this problem). What's needed for this? $\endgroup$
    – fgrieu ♦
    Nov 17, 2022 at 7:47

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