hashcat Forum

(07-08-2012, 04:59 PM)undeath Wrote: [ -> ]no. crypt uses PBKDF2.

you're thinking of pbkdf2-hmac-sha512, like what grub uses. sha512crypt doesn't use pbkdf2. sha512crypt is actually based on md5crypt. see https://www.akkadia.org/drepper/SHA-crypt.txt

either way OP, the answer is no. you cannot convert a raw sha512 hash to sha512crypt or vice-versa.

hashcat CPU can crack sha512crypt

(07-09-2012, 05:22 AM)epixoip Wrote: [ -> ]you're thinking of pbkdf2-hmac-sha512, like what grub uses. sha512crypt doesn't use pbkdf2. sha512crypt is actually based on md5crypt. see https://www.akkadia.org/drepper/SHA-crypt.txt

as far as i know [md5]crypt in fact uses PBKDF2.

(07-09-2012, 12:32 PM)undeath Wrote: [ -> ]as far as i know [md5]crypt in fact uses PBKDF2.

no sir.

And how can I crack a salted sha512 hash with hashcat? I tried it, but hashcat didn't work with this ASCII-string from the shadow file.

In fact the sha512 algorithmus is working with a binary-code and then the output is transformed into a hex-string. Why is output of crypt a ASCII-string.

Please understand sha512crypt, aka SHA512(Unix), is *not* simply salted sha512. The "hex string" generated by Cain's Hash Calculator is just a raw sha512 hash, and is completely different -- and in no way compatible with -- sha512crypt in libc. The "ASCII string" that crypt outputs is base64-encoded, and is the result of 5,000 rounds of the sha512 algorithm.

You can use -m 1800 in the cpu version of Hashcat to crack the sha512crypt hashes from your shadow file.

Thanks a lot. I think now I understand it.

But I've still a problem with the hashcat syntax.
I made a hash on linux:
Command
(Password: 1)

Quote:$6$OAvo4U/8$axO2kf4GzAWhSvq2l9r5nsFMQG0o61cCVu0RzjmoM3qAZ1kskvqCpnIXn.d7B04UbEoMwYQ1ehfTw5QWit1Px1

It's allready salted.

And now I tryed to crack this one.


Well I know, only the part after the third $ is the pw and this is the wrong syntax pritty sure, but I tryed some other configurations and no one worked.

Beside this there is no -m 1800 in the --help text

Dude, oclhashcat-puls can NOT crack SHA512(Unix).
Use hashcat-0.39 (The CPU version).

Sry, now I got it. I tryed it an cracked some pw's, but it's very, very slow, if the calculation is done by the CPU. Why isn't this possible with CUDA. I think there is no chance to crack sha512unix pw's with more than 5 chars and a well chosen charset. But it would be more interesting with cuda. Is there maby another programm which supports sha512unix cracking with cuda?

In fact, sha512unix is not very much faster on GPU as compared to CPU. If bruteforcing 5-char passwords is not practical on CPUs (your charset is too large?), then it's very likely it won't be practical on GPUs too.

The algorithm itself is moderately GPU-unfriendly because of the 64-bit operations that are not natively supported on GPUs and are emulated in software. But the biggest problem is that the GPR pressure is so high that you cannot utilize the hardware properly. The GPU just cannot run enough wavefronts due to limited resources and ALU units end up underutilized. There is also a paradox, under certain circumstances, sha512unix can be made faster by offloading part of the algorithm on the CPU rather than doing all of it on the GPU.