Hack The Box solution: xorxorxor

We have the code to encrypt the flag:

The code will generate a random key with the length of 4. Then XOR each byte of the flag with each byte of the key.

We know the flag starts with ‘HTB{‘, and the output is:

134af6e1297bc4a96f6a87fe046684e8047084ee046d84c5282dd7ef292dc9

From the code, we can see that each character will be XOR with each character of the key and the length of the key is 4 characters.

For example: The first charater (H) XOR the first character of the key –> 13

The second charater (T) XOR the second character of the key –> 4a

The third charater (B) XOR the third character of the key –> f6

The fourth charater ({) XOR the fourth character of the key –> e1

We can use CyberChef for XOR Brute Force.

HTB{ (text) --> 4854427b (hex)
48 XOR 5b --> 13
54 XOR 1e --> 4a
42 XOR b4 --> f6
7b XOR 9a --> e1

Then we can easily find the key is: 5b1eb49a

Decrypt the output, we can find the flag.

Flag: HTB{rep34t3d_x0r_n0t_s0_s3cur3}

CTFlearn solution: Tone dialing

In this challenge, we have a wav file. Open it, the sound is like when pressing phone numbers, it is DTMF (Dual-tone multi-frequency signaling).

Then, we use a DTMF decoder, and the number string is:

67847010810197110123678289808479718265807289125

Change this to text, we have the flag.

Flag: CTFlean{CRYPTOGRAPHY}

CTFlearn solution: Modern Gaius Julius Caesar

In this challenge, we have a string: BUH’tdy,|Bim5y~Bdt76yQ

And the hint is: “Why should you when you have your keyboard?”

This is just Keyboard Shift Cipher with Shift Direction is Right and Shift Amount is 2.

Decode it and we have the flag.

Flag: CTFlearn{Cyb3r_Cae54r}

CTFlearn solution: Suspecious message

This picture reminds me of Playfair cipher, so I used this tool to decode it.

Flag: CTFLEARN{PL4YF41R_1S_C00L_C1PHERRRR}

CTFlearn solution: 5×5 Crypto

5×5 Crypto is an example of Polybius Cipher, then we will use www.dcode.fr/polybius-cipher to decode it.

We need to create a 5×5 grid without K and find the string.

Flag: CTF{THUMBS_UP}

CTFlearn solution: RSA Noob

In RSA algorithm:

c = m^e mod n

In the text file, we have

e = 1

so we can guest that

m = c + x * n with x in {0, 1, 2, 3…}

With x = 0, we change c into hex.

Then, we change hex into text.

Flag: abctf{b3tter_up_y0ur_e}

CTFlearn solution: Substitution Cipher

We need to use a Substitution Solver to decode the string in the file. Then, we have:

THE FLAG IS IFONLYMODERNCRYPTOWASLIKETHIS. GENERATED BY MARKOV CHAIN OF THE WIKIPEDIA PAGE ON CALVIN AND HOBBES…

CTFlearn solution: Hextroadinary

“Meet ROXy, …”

The hint is “ROX” which means we need to use a XOR calculator (or another XOR calculator) to find the flag.

Flag: 0xc0ded

CTFlearn solution: HyperStream Test #2

“I love the smell of bacon in the morning!”

The hint show that it is Bacon’s cipher encoded, so we decode it.

Flag: ILOUEBACONDONTYOU

CTFlearn solution: Morse Code

We just need to decode the string.

Flag: FLAGSAMUELMORSEISCOOLBYTHEWAYILIKECHEES