DHA Challenge 2023-04 (Solution)

It’s been three months since the “Unselected Keys” challenge was released at Dallas Hacker’s Association (DHA), so it’s time to reveal the solution. If you haven’t played it yet and would like to, you can find the challenge here. Continue past the break if you’re ready to see the full solution!

The first phase on this challenge is a word search. You need to find all of the listed words as well as one additional word that is referenced but not identified. That word is “steganography”:

The text below the crossword says “A word may be found which is not in the list; using it unlocks the final twist! What was not used may just fit the bill… Credit it to Bellaso who is rarely credited still.”

The word which is not found is of course “STEGANOGRAPHY”. A quick Google search will reveal the name “Giovan Battista Bellaso” and a corresponding Wikipedia page which shows that “The Vigenère cipher is named after Blaise de Vigenère, although Giovan Battista Bellaso had invented it before Vigenère described his autokey cipher.” This points to using what is commonly referred to as a Vigenere Cipher.

Vigenere Ciphers take ciphertext and a specified key to reverse back to plaintext. In this case, the comment that “using it unlocks the final twist” indicates that “STEGANOGRAPHY” is the key. Using it with all of the letters that were not selected gives the answer.

Unselected letters from the puzzle:

UHRMRNHACAIPMFL ST MNYOEG XA RZBW LAE BUN TD MGFBWN YBIX JOABRAHR LIAR NVRBPR SGH
ZEYZ NZM IOYL MLK SRQXVT IV ZWMXKR YWBZNV JYF UI LOHBJ SEAVU OAIXE GVK NAILPK MSACU HNV SZF WOIXYGVOEG QLWGGH ZHVG OJ JJZR XBPREE OTU CPU ZW LELEYM OXNDYCV NRREFG EFU GLYDEC RIXS RRTXU YT TFASH OJ LSJT LGG ZGLRH IFNHLOMXRZIN OHPSHBQ SUCYSHA OEVDJYL FEXE NAOTUH JYWEYS NBB GEIBBK ENXGNG EAZ TGHLK FEXE PIXIUCA

Decrypted using “STEGANOGRAPHY” yields:

CONGRATULATIONS ON MAKING IT THIS FAR NOW TO FINISH YOUR SOLUTION FIND HERMIT AND TELL HIM THAT THE SECRET TO BETTER LIVING CAN BE FOUND BELOW WHERE THE WATERS TOUCH THE SKY EVERYTHING BEYOND THIS IS JUST FILLER AND CAN BE SAFELY IGNORED UNLESS YOU REALLY LIKE LATIN AB ABUSU AD USUM NON VALET CONSEQUENTIA ABYSSUS ABYSSUM INVOCAT MARE AMICUS CAELUM NON ANIMUM MUTANT QUI TRANS MARE CURRUNT

And… #Victory 🙂