John the ripper charset

Hey all, I have a question about John the Ripper.
I know that a password that is 7 characters long and used only 4 keys. I know what the three keys are, but I don't know how to make a custom charset. I have edited the john.conf file to have the following:

Code:

---

[Incremental:Custom]
File = custom.chr
MinLen = 7
MaxLen = 7
CharCount = 3

---

Now i just don't know how to make the custom.chr so that it only contains the 4 keys 'asdf'
Any ideas?
Thanks

I am confused :confused:

If you have 4 characters, why have you set "CharCount = 3" ?

Also, don't you need to declare a, s, d, f as your character variables?

:confused:

Yes, sorry nihil that was a typo. I have CharCount=4.
And i guess my question is HOW do i declare my variables as a,s,d,f? From what I can gather the character sets are locked up in the .chr files, but they aren't ascii so I can't just make one.
There is the -make-charset flag, but i must not be using it properly because it expects a file.