ritheachengkh

Bandit Level 11 → Level 12

Level Goal

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

Commands you may need to solve this level

grep, sort, uniq, strings, base64, tr, tar, gzip, bzip2, xxd

Helpful Reading Material

Rot13 on Wikipedia

🔑 Solution

ssh bandit11@bandit.labs.overthewire.org -p 2220

Then enter the password obtained from the previous challenge.

After using the ls and cat commands to examine the data, we determined from the instructions that it is a ciphertext encoded with a ROT13 cipher.

ROT13 (Rotate by 13) is a type of Caesar cipher, which is a substitution cipher where each letter in the alphabet is replaced by another letter a fixed number of positions away.

The following command can be used to decode the cipher.

cat data.txt | tr 'A-Za-z' 'N-ZA-Mn-za-m'

tr stands for translate. It replaces characters in the input.
'A-Za-z' means: all uppercase A to Z and lowercase a to z.
'N-ZA-Mn-za-m' means: shift each letter 13 places (ROT13 logic). A–M → N–Z, N–Z → A–M, Same for lowercase

Alternatively, the cipher can be decoded manually using a table.

#	Plain	ROT13		Plain	ROT13
1	A	N		N	A
2	B	O		O	B
3	C	P		P	C
4	D	Q		Q	D
5	E	R		R	E
6	F	S		S	F
7	G	T		T	G
8	H	U		U	H
9	I	V		V	I
10	J	W		W	J
11	K	X		X	K
12	L	Y		Y	L
13	M	Z		Z	M

There’s also a web-based tool called CyberChef that can help with deciphering this.

Congratulations! You’ve found the flag for the next challenge.