90% Reduction in performance when adding a single character

90% Reduction in performance when adding a single character - Printable Version

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90% Reduction in performance when adding a single character - ipen - 01-23-2024

Hi folks,

Reaching out because I am at a loss.

In a nutshell, this command has me at 4500mh/s on a 4090:

Code:
hashcat -a 3 -O -m 22500 --hex-charset w.txt -1 61626364656667686A6B6D6E707172737475767778797A41424344454647484A4B4C4D4E 202020?1?1?1?1?1?1?1?1

But adding a single character to this results in a 90% reduction in performance, starts hashing at 450mh/s:

Code:
hashcat -a 3 -O -m 22500 --hex-charset w.txt -1 61626364656667686A6B6D6E707172737475767778797A41424344454647484A4B4C4D4E 20202020?1?1?1?1?1?1?1?1

Util of the GPU is curious in the second instance: idle-busy-idle-busy-idle-busy. Hashcat's util numbers mirror what is illustrated in the attached image.

Something simple I am perhaps missing?

RE: 90% Reduction in performance when adding a single character - royce - 01-24-2024

There is a known "bias" built into hashcat - a byproduct of how it optimizes for speed - that makes static components of the first four bytes on the left-hand side less performant.

RE: 90% Reduction in performance when adding a single character - ipen - 01-24-2024

Ah ok got it, thanks. Good to know I was not doing something stupid. I introduced a -2 2021 which got the speed back but also obviously exploded the problem set.

Any other way to work around this?

RE: 90% Reduction in performance when adding a single character - Snoopy - 01-24-2024

(01-24-2024, 03:03 AM)ipen Wrote: Ah ok got it, thanks. Good to know I was not doing something stupid. I introduced a -2 2021 which got the speed back but also obviously exploded the problem set.

Any other way to work around this?

without knowing the outcome, what about trying to use a hybridattack? wordlist + mask?

dont know how this affect the 4byte bias mentioned by royce, but think its worth a try

so your input wordlist would be just a single line with 4 spaces, thenn add the rest of the mask

or you could generate lets say a wordlist with all possiblities of first 8 bytes given your hexinput, didnt do the math right now, if its to many combinations forget that

RE: 90% Reduction in performance when adding a single character - ipen - 01-24-2024

(01-24-2024, 01:15 PM)Snoopy Wrote:
(01-24-2024, 03:03 AM)ipen Wrote: Ah ok got it, thanks. Good to know I was not doing something stupid. I introduced a -2 2021 which got the speed back but also obviously exploded the problem set.

Any other way to work around this?

without knowing the outcome, what about trying to use a hybridattack? wordlist + mask?

dont know how this affect the 4byte bias mentioned by royce, but think its worth a try

so your input wordlist would be just a single line with 4 spaces, thenn add the rest of the mask

or you could generate lets say a wordlist with all possiblities of first 8 bytes given your hexinput, didnt do the math right now, if its to many combinations forget that

I'll give this a bash, thanks