DC34 Badge — Flag Hunt Notes & Tools

Working notes and offline tooling for the DEF CON 34 badge light-exchange / flag challenge.

This repo does not contain the badge firmware. It holds analysis, a small offline Ko cracker, and helpers that sit next to the official bunnie / betrusted sources.

Official badge help: defcon.org/34b.

Expected layout under ~/dev (or wherever you work):

dev/
├── dc34-badge/      ← this repo
├── dc34-vault/      https://github.com/bunnie/dc34-vault
├── dc34-console/    https://github.com/bunnie/dc34-console
├── dc34-api/        https://github.com/bunnie/dc34-api
├── dc34-core-hw/    https://github.com/bunnie/dc34-core-hw
├── dc34-image/      https://github.com/bunnie/dc34-image
├── dc34-bio/        https://github.com/bunnie/dc34-bio
└── xous-core/       https://github.com/betrusted-io/xous-core

mkdir -p ~/dev && cd ~/dev
git clone https://github.com/jonfen/dc34-badge
git clone https://github.com/bunnie/dc34-vault
git clone https://github.com/bunnie/dc34-console
git clone https://github.com/bunnie/dc34-api
git clone https://github.com/bunnie/dc34-core-hw
git clone https://github.com/bunnie/dc34-image
git clone https://github.com/bunnie/dc34-bio
git clone https://github.com/betrusted-io/xous-core

# Install rustup if needed: https://rustup.rs/
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
source "$HOME/.cargo/env"

rustc --version   # tested with 1.97.1; any recent stable is fine
cargo --version

No RISC-V target is needed for the cracker — it is a host (x86_64 / aarch64) binary.

Python 3 with the stdlib only (base64, zlib). No pip packages.

USB CDC serial at 115200 baud on /dev/ttyACM0 (Linux / WSL2). You need membership in dialout (or equivalent):

sudo usermod -aG dialout "$USER"   # then re-login
# tip: picocom / screen / minicom at 115200 8N1

Image upload (separate tool in dc34-image) uses 1_000_000 baud.

cd ko_cracker
cargo build --release
./target/release/ko_cracker selftest          # proves encrypt → verify → search
./target/release/ko_cracker selftest --bits 24
./target/release/ko_cracker --help

Point it at a real exchange once you have the two QR payloads (see analysis doc):

./target/release/ko_cracker crack \
  --key '????????????<52 hex of public Kp for the day>' \
  --req-qr '<REQUEST_QR_TEXT>' \
  --resp-qr '<RESPONSE_QR_TEXT>'

Or raw hex: --nonce <12B hex> plus --ct-tag <32B hex>.

Day-4 reality check: a 48-bit search is GPU-scale (~1 day on an RTX 4090 per the scheme doc). This crate is a correctness reference (~10 Mkeys/s on CPU); port the verify() loop to a GPU for a serious crack.

• Do not flash a developer image unless you accept wiping flag #1, Ko, and light exchange (one-way into developer mode).
• Do not send the factory test k0 <base64> vectors to a production badge — that overwrites Ko.
• Prefer capturing one exchange transcript and cracking offline. Ko is shared across all badges, so any badge's transcript works and nothing is wiped.

Details, dead ends, and the full capture procedure: FLAG_HUNT_ANALYSIS.md.

• Flag #1 (THE_FLAG_1, RRAM slot 260): wiped before developer mode — fault injection only (standing bounty).
• Flag #2 ("somewhere else"): not in the erase set; needs a sacrificial badge + survivor dump (destructive).
• Non-destructive Ko path: capture light-exchange QRs → brute force with public Kp (recommended).
• ko_cracker is built and self-tested; only missing input is a real transcript.

Analysis and tooling here are personal notes for the DC34 badge challenge. Firmware copyright remains with the original authors (bunnie / betrusted / Baochip). See the linked upstream repos for their licenses.