Speed reduction

[ankur]

Input.Mode.....: Mask (?d?d?d?d?d?d?d?d?d?d?d?d?d111) [16]
Speed.GPU.#1...:  2877.0 MH/s

Input.Mode.....: Mask (111?d?d?d?d?d?d?d?d?d?d?d?d?d) [16]
Speed.GPU.#1...:   611.1 MH/s

[epixoip]

Left half of the mask is too small to gain any acceleration. Learn how the program works.

[ankur]

Input.Mode.....: Mask (1?d?d?d?d?d?d?d?d?d?d?d?d?d?d?d) [16]
Speed.GPU.#1...: 2915.3 MH/s

[ankur]

Why does speed reduces so much when the mask is 111?d?d?d?d?d?d?d?d?d?d?d?d?d ?

[epixoip]

Because the left mask keyspace is too small and therefore you're not giving the GPU enough work to do.

[atom]

What epixoip means is the following, take the first 4 chars:

Input.Mode.....: Mask (?d?d?d?d?d?d?d?d?d?d?d?d?d111) [16]

?d?d?d?d = 10 * 10 * 10 * 10 = 10000

Input.Mode.....: Mask (111?d?d?d?d?d?d?d?d?d?d?d?d?d) [16]

?d?d?d?d = 1 * 1 * 1 * 10 = 10

What oclHashcat ideally needs, is a number > 256 to archieve full speed. There's no way to "fix" this because it's not a bug. For detailed information why it's not possible to change this read this: https://hashcat.net/events/p13/js-ocohaaaa.pdf page 23.

There's however a way to solve this for your special use case by using a salted variant of your hash. For example in case you try to crack sha1, take -m 120 and generate a file:

b89eaac7e61417341b710b727768294d0e6a277b:111

And then instead of using the mask:

111?d?d?d?d?d?d?d?d?d?d?d?d?d

use:

?d?d?d?d?d?d?d?d?d?d?d?d?d