Efficient way to crack 8 chars passwords

[id417]

Hello folks,

I'm looking for an efficient way to crack ~700 hashs of DES crypt (hash-mode = 1500).
(cracking power for this task: hashcat runs on 3 old GPUs. In wordlist+rules mode, it gets ~400MH/s.)

Knowledge
All passwords are 8 characters long.
In addition, they use at least 3 types from the following:
- lowers
- uppers
- digits
- specials

Issue
I tried using my favourite wordlist+rules but the workload will contain a lot of candidates which are not valid (because not exactly 8 characters long).
A pure bruteforce seems not effective since they use a wide range of characters.

Experiments
In order to reduce the workload to 8 chars long candidates, I tried something like:

Code:

mkfifo grepHashcat
./hashcat64.bin -r all.rules--stdout wordlist.txt | grep '^.\{8\}$' > grepHashcat &
./hashcat64.bin --username -m 1500 hashlist.txt < grepHashcat

Using this solution, it is not possible to see the estimated time so it is not possible to adjust rules and wordlist.

I also tried to create a rule file containing "_8" to reject all candidates not equal to 8 characters.
But it seems not possible to apply this rule after applying all.rules in order to reject candidate and not plain.

Question
Do you know any solution in order to efficiently reduce the workload based on what we know from the plain text passwords?

Many thanks,

id417

[atom]

- instead of using a fifo you can use a pipe
- you dont save the grep, hashcat rejects > 8 by default for descrypt