Cryptographic Puzzle Challenges/sandwich

This is the writeup for the Cryptographic puzzle challenge posted by Thor on the 20th of November 2023

given was a file called "Sandwich" which is downloadable.

This file is a zip file, so adding ".zip" to the end of the filename makes it an extractable archive.

Inside we can find 2 Files.

A text file called "Curious.txt" with the content

PHONE 45797137 BEAST

A 21x21 sized image called "CaesersThree.png"

Scrambled QR Code

The text from the text file translates into a telnet command with IP and Port as first found out by Discord User piolix000.

telnet 45.79.71.37 666

The Image needs to be Bitflipped via the QR Code Mask Pattern 111 - figuring this out took the #cryptography channel 9:58 hours.

The most substential work in this channel for this was done by the discord users by the name of Interacsion, dot krl and Notjon, with Interacsion being the first to figure it out and share it and bendtheory being the close second.

In short there are Bit Masks for QR encoding that have to be used here to get a readable QR Code.

For this the encoded QR code has to be overlayed with the mask, which is tiled to make an 21x21pixel image - equivalent to the dimensions of the CeasersThree.png

Every Pixel where the Mask is coloured, the Pixel in the CeasersThree.png needs to be flipped - Is it black, make it white and vice versa - until a device readable QR code is revealed

The raw, encoded QR code is overlayed with the Mask and the bits in the source image are flipped accordingly to reveal the QR code

After connection via telnet and entering the Password form the QR Code we are greeted with the next puzzle

If the QR code is read with a device, it reads out "Hack The Box" which is the password for the telnet connection

For this either a command line with the telnet client, or a telnet-able Software like Putty is required

On connecting to the server, a password is asked which as we learned from the QR Code is "Hack The Box"

Sing me the song. ,.;'*
The song of the green one with the little... ^
He with the shining blade of beams. o=|===>
The song of angered clouds and crackling sky.
Sing it like the dwarves in their forts of old.

To "play the notes" we need the song first. the Puzzle refers to the Song of Storms from from Zelda: Ocarina of Times

"Playing the Notes" yields the final Puzzle

The Special chars at the end of the first line are a hint to the 5 different notes used in the song The Notes this Puzzle is looking for are ,.',.'

this is answered by Thors server with what seems to be a product key.

First one to figure this out was the Discord User Vidra, with everyone in the cryptography channel thinking its over

However, the given string is Vigenere encrypted as figured out by (ﾉ◕ヮ◕)ﾉ*:･ﾟ✧ Goblin in the cryptography channel.

the string decrypted by Vigenere using the Key "HACKTHEPLANET" yields the final flag which is also the product key for a year of Hack The Box Academy Silver.