# Thread: Crunch password list with exact length and number of letters and numbers known

1. ## Crunch password list with exact length and number of letters and numbers known

i am trying to create a wordlist with crunch i only need all possible passwords exactly 20 digits/letters long with exactly 19 letters (a-z) and 1 number (0-9) is there a way to do that?

2. ## Re: Crunch password list with exact length and number of letters and numbers known

Sure you would do it like this:

crunch 20 20 abcdefghijklmnopqrs9 > passwordlist.txt

3. ## Re: Crunch password list with exact length and number of letters and numbers known

i need the command to make a 20 digit 19 letters one number calculation in the form of for example "abcdefghijklmnopqrst1" (places interchange) but with the complete alphabet and the numbers from 0 to 9. Is this command accurate for that?

4. ## Re: Crunch password list with exact length and number of letters and numbers known

Originally Posted by purehate
Sure you would do it like this:

crunch 20 20 abcdefghijklmnopqrs9 > passwordlist.txt
I am sorry. I am new to BT4. When I type above commond in in BT4. It returned command not found. I booted up using a CD. How do I get above command to work?

5. ## Re: Crunch password list with exact length and number of letters and numbers known

If you know where the number is in the password you can download crunch 2.3 from crunch - wordlist generator | Get crunch - wordlist generator at SourceForge.net which supports specifying the locations of letters and numbers.

6. ## Re: Crunch password list with exact length and number of letters and numbers known

The number could be at any place in the password thats why i want to create an (19^26)*200 passwords list to have all possible combinations. I am just looking for the right command to exclude all passwords with more than one number.

7. ## Re: Crunch password list with exact length and number of letters and numbers known

Purehates command is probably the best way.

Also your formula is wrong. The formula to calculate the size of a wordlist is (x^y)*(y + 1) and you have x and y switched.
It should be num-of-chars ^ length so (27^20)*(20+1). So 890,214,323,779,540,273,800,183,097,221 bytes or 890,214 YB (Yottabytes). I don't think you have enough disk space for such a file.

8. ## Re: Crunch password list with exact length and number of letters and numbers known

thanks my mistake. According to one study, all the world's computers store only approximately 160 exabytes. i will try with smaller passwords and let one machine compute for one or two months and hope that i get lucky.

But could you explain the math a little bit?

I thought if i had 19 possible characters and 10 possible numbers with in a 20 digits/letters password and i could eliminate all possibilities i would have 19^26 possible combinations off letters * (10*20) numbers = 2.279.779.037.074.628.864 combinations. So only 2.3 EB (Exabytes).

Where did I get wrong?

9. ## Re: Crunch password list with exact length and number of letters and numbers known

Of course you can generate large wordlists and run into storage problems however there is a bigger problem. Most applications in BT4 can only handle 2GB or less sized files. 2GB is the maximum filesize for 32-bit OSs. Yes there are workarounds (crunch uses them) but john the ripper and aircrack can't use a wordlist greater than 2GB in size. Then there is performance impact. To maximize performance you should have enough free RAM to store the wordlist in RAM. If you have a 2GB wordlist with 1GB of RAM performance will be horrible.

10. ## Re: Crunch password list with exact length and number of letters and numbers known

hi sorry to jump into this thread, but it is relevant to what i am also trying to find out

i want to make a wordlist of only uppercase A - Z and only 8 characters long, after reading the posts in the forum i found crunch and the command i needed to use to get what i want, thanks for that

my question is as follows, a 56gb file (the one i specified in crunch command) was made quite quickly in the crunch folder and the pc is plugging away still 18 hours later filling it with (i hope) all the possible combinations i asked for...

after reading this thread and another it seems that my resulting list should in fact be much, much bigger

am i correct with the following?

(26 ^ 8) * (8 * 1)
208827064576 * 9 = 1879443581184

like in the other post using google to do the diskspace math gives me
(26^8) * 9 bytes = 1.70934398 terabytes

if this is correct then i may as well abort as i have nowhere near this amount of space...