DEF CON 23
Table of Contents
1. Overview
DEF CON 23 (August 6–9, 2015). Paris & Bally's, Las Vegas.
The badge was a playable vinyl record — a 7" LP with encoded text on both sides and DTMF audio tones at the end of the recording.
2. Badge Cipher
The DC23 badge used multiple encoding layers, solved collaboratively by attendees over the weekend:
2.1. Shavian Alphabet (Substitution)
The primary cipher: text printed on the badge in the Shavian phonetic alphabet — a one-to-one substitution between Latin letters and Shavian glyphs. Bijective. Decoded by identifying the crib word "science."
Badge variant decoded messages:
- Human badge: "Mystery is the source of all true art and science."
- Blue badge: "be cool but care"
- Green badge: Constitutional rights passage
2.2. ROT13
The conference program contained ROT13-encoded text:
VgjbhyqagorQrspbajvgubhgbhetbbqsevraqPnrfne
Decoded: "It would not be Defcon without our good friend Caesar" — a self-referential nod to Caesar ciphers.
Try it: decode in the tool.
2.3. Pigpen Cipher (Lanyard)
The badge lanyard featured a Pigpen cipher — a geometric substitution where letter position in a grid determines the glyph shape. Bijective.
2.4. DTMF Audio (Vinyl Record)
The vinyl record contained DTMF (Dual-Tone Multi-Frequency) tones at the end of the audio. This is steganographic: the "decode" is a domain transform (audio → frequency detection → digits), similar to the Aphex Twin spectrogram technique.
2.5. Poe's Gold-Bug Reference
Additional ciphertext referenced Edgar Allan Poe's "The Gold-Bug" (1843) — the story that popularized frequency analysis as a decryption method. See the reversible pipeline examples for the Gold-Bug's place in the cipher lineage.
3. 1o57 Badge Contest — 11-Step Pipeline
1o57's DC23 badge contest (separate from the vinyl badge above) was an 11-step ARG. Full walkthrough: Potato Hat Security / Council of Nine.
| Step | Encoding / Technique | Output |
|---|---|---|
| 1 | Telugu script (phonetic substitution) on hotel keys | LITTLE GIRL RECORD TWO FIVE |
| 2 | ROT13 in booklet + keyed Vigenere (key: LASTORY) | "GET THE BLUE KEY…" |
| 3 | Password-protected RAR (MysteryFolder.rar) |
Thetruthisoutthere. |
| 4 | Vinyl record: number station + DTMF → T9 | red key passphrase |
| 5 | Lanyard: Nyctograph + Gold-Bug → Playfair cipher | reenigne.engineer URL |
| 6 | Reverse("engineer") → reenigne.engineer |
X-Files references |
| 7 | Logic gate schematic → hex → LostboY.net/3E01A |
circuit-as-transform |
| 8 | Portobello Road (Bedknobs & Broomsticks) images | Vigenere key: TREGUNA MEKOIDES… |
| 9 | Number station + Vigenere → eigen space dot product | eigen.space URL |
| 10 | Doppler-shifted image → Coagula spectrogram | unallocated.space URL |
| 11 | Atomic number encoding → phone number → Spirit DVD code | TITIVILLUS@MYSTERIOUSBOOKS.NET |
Encodings used: ROT13, keyed Vigenere, T9/DTMF, Playfair, Nyctograph, Gold-Bug substitution, logic gates (AND/OR/XOR), spectrogram steganography, atomic number lookup, Spirit DVD code.
The MysteryFolder.rar has been extracted (password from step 6):
DigitalFun.jpg— logic gate schematic producing hex3E01AHaunted Mansion.mp3— audio artifactSuperNova.JPG— image artifact
4. Badge (Physical)
I have the vinyl record badge.
TODO: photograph and add image.
5. References
- Hackaday: Help Decipher the DEF CON Badge
- Hackaday.io: DEF CON 23 Badge Hacking project
- Encode tool — decode badge ciphers interactively
- Reversible Pipeline Transforms — the theory