[jacquesm]

> The thing is you don't know the length of the password. It could be more than the number of hydrogen atoms in the universe, or 12.

I'll take 12 then.

[bushbaba]

Well we know it has to fit in a string data type. And there’s only soooo much ram available to a JavaScript variable.

[AdamJacobMuller]

Not necessarily. The hash could have been generated with something other than javascript.

In fact because functions like sha256 are iterative it's possible to hash a password which is longer than the RAM in a system. Technically possible to hash a password which is longer than storage in a system too, if you don't care about storing the password.

[kzrdude]

so the puzzle author could "cheat" and just present a 256-bit number and not know the preimage at all, which would be a fun shortcut.

[mulmen]

Huh, I realize I don’t know the answer to this seemingly simple question. Are all 256 bit vectors valid sha-256 hashes?

[talkin]

Yes.

In a secure hash function, all output bits are without bias. So all combinations exist.

[kzrdude]

Sounds like the ideal. Can we prove that sha256 has this property?