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0 pointskzrdude4y ago0 comments

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.

0 comments

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

Yes.

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

kzrdudeOP4y ago

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

j / k navigate · click thread line to collapse

0 pointskzrdude4y ago0 comments

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.

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

Yes.

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

kzrdudeOP4y ago

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

j / k navigate · click thread line to collapse