CDC 2017 Puzzle 4 – Achevare

Solution: Click Decrypting Achevare to view the documentation on how to solve Puzzle 4 – Achevare.

Puzzle 4 Winners: Congratulations to the following participants who successfully solved Puzzle 4– Achevare:

Roland Varriale (Submitted: Wed 2/1/2017 12:06 PM)
Nathan Harmer and Brian Vertullo of Dakota State University (Submitted: Wed 2/1/2017 1:41 PM)
Jocelyn Murry of Wakefield Memorial High School, with the help of Tech Integration (@whsconnect) (Submitted: Wed 2/1/2017 4:28 PM)
Jeff Mathew, Graham Mulvihill, and Matthew Tringone of St. Johns University (Submitted: Thu 2/2/2017 12:06 AM)
Kiran Bhadury of UC Davis (Submitted: Fri 2/3/2017 12:50 AM)
Andy Huttenga (Submitted: Fri 2/3/2017 7:58 AM)
Daisuke Kondo (Submitted: Sun 2/5/2017 8:02 AM)
Brandon Pelc of University of Illinois at Urbana-Champaign (Submitted: Mon 2/6/2017 1:14 AM)
Nicholas Losby (@blurbdust) (Submitted: Mon 2/6/2017 1:16 AM)
Brian Sutton of St. Ambrose University (@brsutton1978 ) (Submitted: Mon 2/6/2017 6:53 PM)
Oliver Hui, Daniel Moreno, Michael Baccia, Chase Lee, Daniel Stempniewicz, Rigel Gjomemo, and Shawn Kim of University of Illinois  Chicago (Submitted: Tue 2/7/2017 7:52 PM)
Ramandeep Singh of Lewis University rdsece (Submitted: Mon 2/20/2017 11:17 PM)
Brandon White(@BrandonPWhite) (Submitted: Tue 2/21/2017 8:04 PM)
Angel Valdez of Lewis University (Submitted: Sat 3/4/2017 11:44 PM)

Hint 1:  I can see that all of you have done very well, but the “Save them.pdf” seems to cause people to dwell.  There is no trick hidden within this image, just follow the link below to continue your pilgrimage:
https://www.docdroid.net/LFrMOa4.
The password to unlock the doc is in hex… now off you go, and onto the next!

Hint 2: The Pontifex cipher is tricky indeed, but if you order the deck and follow this decryption method, you’re sure to succeed:

Decryption:

1. Convert the encrypted message letters to their numerical equivalent
2. Setup the deck of cards according to your key (as laid out in the Pontifex PDF).
3. Follow this algorithm:The algorithm is the same for both encryption and decryption, and is executed in five steps. Before starting the algorithm, you may want some page markers to attach to the jokers with “A” and “B” on the marker, to make it easier to search through the deck looking for Joker A and Joker B. Here are the steps necessary to produce the keystream letters:
   • Step 1.  Find Joker A– Identify the location in the deck of Joker A, and move it down one card (swap it with the card beneath it). If Joker A is on the bottom of the deck, treat the deck as a circular deck, and move it just below the top card.
   • Step 2.  Find Joker B– Identify the location in the deck of Joker B, and move it down two cards. If Joker B is on the bottom of the deck, treat the deck as a circular deck, and move it just below the second to top card. If Joker B is the second to bottom card, move it just beneath the top card, again treating the deck as a circular loop.
   • Step 3.  Perform a triple cut– Identify the locations of the top-most and bottom-most jokers. Cut the cards above the top-most joker and the cards below the bottom-most joker. Swap the top-most cut with the bottom-most cut. That is, the cards above the top-most joker are placed beneath the bottom-most joker. And the original cards beneath the bottom-most joker are placed on top of the top-most joker.
   • Step 4.  Perform a count cut– Identify the numerical value of the bottom-most card in the deck, using the Bridge order mentioned above. If the card is the Seven of Diamonds, then it’s numerical value is 20. Count this numerical value of cards from the top card, and cut them from the deck. Place this cut directly above the bottom-most card. A deck with a Joker as the bottom-most card will remain unchanged in this step.
   • Step 5.  Find the output card– Identify the numerical value of the top-most card in the deck, using the Bridge order mentioned above. Count this numerical value of cards from the top card, and take the numerical value of the next card. Write this value down modulo 26 as your keystream output. If the card is either Joker, star the algorithm over at step 1
4. Write down each key value at the end of Step 5.
5. Subtract that value from your message.
6. Convert modulo 26 using addition.
7. Convert the numbers to letters:

Now, the cards in the deck each have a unique numerical value as follows:

• Clubs: Face value +0
• Diamonds: Face value +13
• Hearts: Face value +26
• Spades: Face value +39
• Jokers: Both value of 53

Need more help? try this

I have just released puzzle four, and I promise you it will not be a bore.

By far the most difficult of them all, the amount of decryption skills you will need for Achevare will not be small.

Thank you for participating in my puzzle game. It’s been fun – I hope you feel the same.

-Puzzlemaster

If you think you have the correct solution, email CyberForceCompetition@anl.gov, and the puzzlemaster will let you know if you have successfully completed your mission.