TexSAW CTF 2026 Idiosyncratic French

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This chall’s got a bit of history to it.

First, crack this initial cryptogram. Now, apply OSINT tools to find who authors that original script.

Flag format: txsaw{first_last} (e.g., txsaw{john_scalzi})

Solution

1. Cryptanalysis: Substitution Cipher

The challenge begins with a large block of ciphertext:

1
Azza wfahv ztu. N rnvy, bndfah na zbfaztv vztak, n vztak ndfa uz n dcnqza zw n uzlvfa, icfuv nmztu...

Using frequency analysis or an automated tool like quipqiup, we can determine that this is a simple substitution cipher. The decoded plaintext is:

Noon rings out. A wasp, making an ominous sound, a sound akin to a klaxon or a tocsin, flits about. Augustus, who has had a bad night, sits up blinking and purblind. Oh what was that word (is his thought) that ran through my brain all night, that idiotic word that, hard as I’d try to pun it down, was always just an inch or two out of my grasp…

2. OSINT: Identifying the Source

The title of the challenge, “Idiosyncratic French”, and the nature of the decoded text provide vital clues.

Searching for the decoded string—specifically unique phrases like “A wasp, making an ominous sound, a sound akin to a klaxon or a tocsin”—reveals that this is an excerpt from the novel “A Void”.

3. The “Idiosyncrasy”: Lipograms

What makes this text “idiosyncratic”? “A Void” is the English translation of the French novel “La Disparition”. The defining characteristic (idiosyncrasy) of both the original and the translation is that they are lipograms: they are written entirely without the letter “e”.

4. Finding the Author

The author of the original French novel, La Disparition, is the famous French writer Georges Perec.

Flag

txsaw{georges_perec}