Level 11
The password for the next level is stored in the file data.txt, where all lowercase (a-z) and uppercase (A-Z) letters have been rotated by 13 positions
Solution
We are dealing with rot 13 algo. Lets use tr command to solve the problem.
From the tr docs
Translate, squeeze, and/or delete characters from standard input, writing to standard output.
CHAR1-CHAR2
all characters from CHAR1 to CHAR2 in ascending order
Lets do some tests.
$ echo "abcdefghjklmnopqrstuvwxyz" | tr [a-f] [A-F]
ABCDEFghjklmnopqrstuvwxyz
$ echo "abcdefghjklmnopqrstuvwxyz" | tr a-f A-F
ABCDEFghjklmnopqrstuvwxyz
$ echo "abcdefghjklmnopqrstuvwxyz" | tr l-w L-W
abcdefghjkLMNOPQRSTUVWxyz
$ echo "abcdefghijklmnopqrstuvwxyz" | tr b-e,u-y B-E,U-Y
aBCDEfghijklmnopqrstUVWXYz
Above we see usage of translate command, now lets build our solution
ABCDEFGHIJKLM
|||||||||||||
NOPQRSTUVWXYZ
So A-M translate to N-Z and N-Z translate to A-M. So A-M,N-Z -> N-Z,A-M
Final Command:
# Seprate handling of lower and upper case letters
$ cat data.txt | tr A-M,N-Z N-Z,A-M | tr a-m,n-z, n-z,a-m
# Single command
$ cat data.txt | tr A-M,N-Z,a-m,n-z N-Z,A-M,n-z,a-m
Solution Screenshot:
Takeaway
- It’s getting Repetitive but RTFM.