+- hashcat Forum (https://hashcat.net/forum)
+-- Forum: Support (https://hashcat.net/forum/forum-3.html)
+--- Forum: hashcat (https://hashcat.net/forum/forum-45.html)
+--- Thread: Limitations of hashcat approach for certain targets (/thread-9902.html)
Limitations of hashcat approach for certain targets - john_alan - 02-26-2021
This is more of a general question around hashcat/JTR style approaches to cracking.
I understand and it's clear how hashcat approaches brute force mask attacks for a multitude of hash types.
However, I understand, in all applied circumstances, one needs a target hash to work towards.
Whether that's from an encrypted word-doc or indeed a bitcoin wallet.dat.
I'm wondering about the limitations of this, is it always possible to obtain such a target hash?
For example I noticed a user trying to attack Scrypt, I can't see how all implementations of symmetric cryptography that use Scrypt for KDF would also "leak" a hash.
As an example, taking a small tool I wrote using libsodium that users ChaCha20-poly1305 to encrypt data with a symmetric key.
A user chosen password is passed through Argon2, thus a key is derived using the Argon2 KDF (a slow HBKDF like Scrypt).
After encryption is complete only the payload of the blob stored on disk looks like this:
[saltForArgon2+nonceAndEncryptedCipherText]
In an example like this, how would one begin to extract a target hash for hashcat? I don't see it as possible.
So, in the case of bitcoin and scrypt support, is the ability to get a target hash from the data implementation specific? or for these examples, does hashcat actually derive a key and try to decrypt AES and check for an output template or something?
Thanks
RE: Limitations of hashcat approach for certain targets - Chick3nman - 02-26-2021
You don't. You don't get a hash.
If your algorithm involves a KDF, we just do the KDF step the same way you would, then do the decryption step on the encrypted cipher text and check if what we got is what we wanted/expected.
RE: Limitations of hashcat approach for certain targets - john_alan - 02-26-2021
(02-26-2021, 03:08 AM)Chick3nman Wrote: You don't. You don't get a hash.
If your algorithm involves a KDF, we just do the KDF step the same way you would, then do the decryption step on the encrypted cipher text and check if what we got is what we wanted/expected.
Makes sense thanks!