Cariad's Crypto Puzzles

Every once in a while, I offer a cryptographic challenge to solve. They're meant to be solvable without the heavy use of any specialised tools. In the past, they were meant for a private group of people or intended for a local security conference, but I have opted to share some of them here.

If you have solved a puzzle, tweet your solution at me!

Current challenge

The following challenge (released December 14th, 2020) can be copied from this text box:

Here are some notes about the ciphertext:

If you're having problems with the contents in the text area, a link to the file containing the data unaltered by the encoding is also available here. No further hints will be provided as that would defeat the challenge!


I like to write ciphertexts and find anything that predates the Enigma as really fascinating and fun. I like to make these sort of things accessible to other people since often cryptography appears to be daunting to tackle. A lot of the puzzles I make are intended to be sort of loosely based on past practices that predate computers and as a result anyone with some knowledge of statistics, a bit of programming to make things quicker and easier, and just a knack for figuring out puzzles and patterns should find this enjoyable.

Previously, these challenges used to be produced as puzzles within conference guidebooks or as a challenge for online communities I have been part of, but I had taken a break for a few years from producing them and as a result of my return to creating new onesI have opted to make them public moving forward.

One of the books I often recommend is Simon Singh's The Code Book (ISBN: 978-1-85702-879-9), which goes deep into the history of cryptography. I can honestly say that if the puzzles you find created by me are not making sense in methodology that upon finishing this book you'll understand what my approach is. His book goes into the mundane methods to quantum cryptography, which to me the latter is basically witchcraft. Additionally, there are puzzles at the back of the book and I've completed a good portion of them myself.

Other books include Cryptography: The Science of Secret Writing by Laurence Dwight Smith (ISBN: 978-0-486-20247-1) and Cryptanalysis: A Study of Ciphers and their Solution by Helen Fouché Gaines (ISBN: 978-0-486-20097-2). These two books are from the late 1930s and early 1940s and as a result predate the public knowledge of encryption and decryption performed by machines like Enigma and Bombe. As a result, I feel like they're good candidates for understanding how to work with ciphertexts.

Past puzzles

I've made numerous puzzles for other events and groups in the past. All of them have been solved as short as a few hours and no longer than a week. Unfortunately, a lot of them have gone missing but as I find more I'll add them to the list.

Title Release date Completition time Comments
Major bets on Surebet September 18, 2017 ~6 days Sent as a gift in late 2016, made public in 2017
Australia and New Zealand at war March 14, 2015 ~2 days Released for BSides Vancouver 2015

Currently, I am trying to hunt down other puzzles for BSides Vancouver 2014 as well as for a message board I used to be active on. If you have a copy of the BSides Vancouver 2014 guide, please do share the puzzle with me as I would love to add this to the list.

Other things

When I write these puzzles, I not only take care of the encryption but I also write the methods to decrypt. This means that any puzzle you see here can be reversed and can be reversed without having to change the code to accommodate the plaintext. This means that all of these puzzles are solvable.

I also do some baseline analysis and purposely make it so you can come up with methods to attack the enciphering process. As a result, these ciphers are not meant to be bulletproof and are not meant to go unsolved for more than a short period of time. Some of my puzzles have been solved in hours and at most have taken a week. Allocate a few hours at least to figuring the puzzles out and do let me know when you have solved them!

Lastly, one big thing: do not write your own encryption methods. This is a bad idea and can endanger yourself and other people either legally or mortally. Lots of time and care goes into creating encyption algorithms and transport standards and I can at least say for myself that I am not qualified to be part of that process.