CODEWITHSUNDEEP
nlp-question-answering
Apple Cider
Apple Cider

Reputation: 51

Known message and output

If the user knows the output from multiple digestions with a different message. Is that able to be so that the user can get the secret?

Example: Can the user find the unknown secret by knowing the following data?

Edit: updated to make a bit more sense.

unknown = ??;
(unknown+"A") = "";
SHA512(unknown+"B") = "";
SHA512(unknown+"C") = "";

.. etc ... ( can continue indefinitely )

can the unknown variable be discovered?

Upvotes: 1

Views: 798

Answers (1)

Nick Johnson
Nick Johnson

Reputation: 101149

No secure hash function allows recovering a valid unknown input faster than brute force, even given a set of known plaintexts and hashes. That includes SHA512.

Also, note that HMAC-SHA512 is not implemented as you're suggesting. A system of SHA512(key+data) is vulnerable to a length extension attack: Given the hash for SHA512(key+"Hi"), an attacker can compute the hash for any string with that prefix, such as SHA512(key+"Hi, I'm a hacker") without knowing the key. The HMAC construction avoids this issue.

Upvotes: 2

Related Questions