writing a mask for a rule

[Snoopy]

this is not possible with one mask, you have use multiple masks or use pregenerated wordlists

ill give you a hint for masks
make a file called masks.txt and add this first line (each line is one mask)

Code:

. ! .! !.?d?d?d?dKnownPartOfTheKey?d?d?d?d. ! .! !.

you can test this with

Code:

hashcat --stdout -a3 masks.txt

this will generate passes like this 

Code:

. ! .! !.4422KnownPartOfTheKey3961. ! .! !.
. ! .! !.6250KnownPartOfTheKey3961. ! .! !.
. ! .! !.1511KnownPartOfTheKey3961. ! .! !.
. ! .! !.0250KnownPartOfTheKey3961. ! .! !.
. ! .! !.2806KnownPartOfTheKey3961. ! .! !.

now you have to specifiy rules for the other combinations lets say 
* 4 digits * 5 digits *
* 5 digits * 4 digits *
* 5 digits * 5 digits *
and also for the null possibility, depending wether or not these "mixing" possibilities are wanted or unwanted (e.g. * null 4digits key 5digits *) you will need, i think, minimal 4 rules max 16 rules for one Key