[Cryptography] SHA-256 decrypted (8 rounds)

[Peter Fairbrother]

On 28/03/2024 10:38, McDair via cryptography wrote:

> When you are using the SHA-256 hash function to protect your secret (what you have done here yourself, or in case of password hashing, bitcoin, ...), you are now using the hash function as an encryption tool.

But you  aren't using the hash to protect the secret.

Not just here, but ever.

I tried to find of think up a use case where a hash was used to protect
a secret, but I couldn't (assuming if cryptographic material is part of
the preimage it is the cryptographic material which protects the secret,
not the hash).

(eg Alice hashes [key][counter][bit] for every bit of her message. Bob,
knowing the key and counter values, hashes [key][counter][0] and then
key][counter][1] and tries to find a match. If he does he gets one bit
of the message, rinse and repeat for the rest of the bits)

> It is also common terminology in such cases to refer to the hash function input message as 'key'.

No, it most certainly isn't. The correct term is image, or preimage.


I note that the wikipedia article on hash functions uses "key", but that
is so full of other errors that I might have to rewrite it completely.
Someone ought to.

The hash table entry is pretty bad too, In hash tables there are
instances where you might call the image a (non-cryptographic) key, but
they use it in other instances where the use of key is wrong.





Common terminology helps us to understand each other, whether it is
warranted or not.

Inability or worse refusal to use it correctly implies you don't want us
to understand you.

And also if you don't use it, people won't bother to read what you say.
There are a lot of new papers to read every day, most of which are
uninteresting or wrong, and if your potential readers find
you don't use the common terminology they will assume you probably don't
know what you are talking about.

You can make up new word usages when doing something new, but not
otherwise. And preimage searching isn't new.


Peter Fairbrother