DEF CON 26
Table of Contents
1. Overview
DEF CON 26 (August 9–12, 2018). Caesars Palace, Las Vegas. Theme: 1983 — the year before Orwell's 1984.
TODO: confirm attendance.
2. Badge
Tymkrs design. PIC32MM + 64-bit LFSR (U7 chip). Text adventure via
serial terminal (115200 baud, /dev/ttyACM0). LED matrix silkscreen
doubled as the game map.
Detailed RE: jwalsh/dc26-badge (local: ~/ghq/github.com/jwalsh/dc26-badge).
Badge archive: media.defcon.org.
3. Badge Cipher — LFSR Stream Cipher
Multi-stage pipeline through a text adventure:
| Stage | Encoding | Notes |
|---|---|---|
| 1 | Hex input | 31-byte ciphertext entered into terminal |
| 2 | LFSR keystream (XOR) | 64-bit mode (U7 chip), or 8-bit mode with seed 0x42 |
| 3 | +=/-= binary |
Intermediate representation |
| 4 | Text output | "You've figured out the secret to life!" |
The LFSR XOR is reversible — same keystream decrypts as encrypts
(self-inverse, like the encode tool's xor 0x42 codec). The seed
0x42 is ASCII B — the same XOR key used in the tool.
The "Bobo" NPC served as the decoder oracle: feed string initializes LFSR state before passing ciphertext. Without sync, the keystream is wrong and output is garbage.
Try the XOR step: XOR 0x42 encode.
4. References
- jwalsh/dc26-badge — local RE notes
- Professor-plum/DefCon26_Badge_Solution
- wchill/defcon26_badgehacking
- Official badge writeup (PDF)
- Encode tool — decode badge ciphers interactively
- Reversible Pipeline Transforms — the theory