Stegstr

Stegstr hides Nostr messages and arbitrary payloads inside PNG images using steganography. Users embed their feed (posts, DMs, JSON) into images and share them; recipients use Detect to load the hidden content. No registration, works offline.

When to use this skill

• User wants to decode (extract) hidden data from a PNG that contains Stegstr data.
• User wants to embed a payload into a cover PNG (e.g. Nostr bundle, JSON, text).
• User mentions steganography, Nostr-in-images, Stegstr, hiding data in images, or secret messages in photos.
• User needs programmatic access for automation, scripts, or AI agents.

CLI (headless)

Build the CLI from the Stegstr repo:

git clone https://github.com/brunkstr/Stegstr.git
cd Stegstr/src-tauri
cargo build --release --bin stegstr-cli

Binary:

target/release/stegstr-cli

(or

stegstr-cli.exe

on Windows).

Decode (extract payload)

stegstr-cli decode image.png

Writes raw payload to stdout. Valid UTF-8 JSON is printed as text; otherwise

base64:<data>

. Exit 0 on success.

Detect (decode + decrypt app bundle)

stegstr-cli detect image.png

Decodes and decrypts; prints Nostr bundle JSON

{ "version": 1, "events": [...] }

.

Embed (hide payload in image)

stegstr-cli embed cover.png -o out.png --payload "text or JSON"
stegstr-cli embed cover.png -o out.png --payload @bundle.json
stegstr-cli embed cover.png -o out.png --payload @bundle.json --encrypt

Use

--payload @file

to load from file. Use

--encrypt

so any Stegstr user can detect. Use

--payload-base64 <base64>

for binary payloads.

Post (create kind 1 note bundle)

stegstr-cli post "Your message here" --output bundle.json
stegstr-cli post "Message" --privkey-hex <64-char-hex> --output bundle.json

Creates a Nostr bundle; use

stegstr-cli embed

to hide it in an image.

Example workflow

# Create a post bundle
stegstr-cli post "Hello from OpenClaw" --output bundle.json

# Embed into a cover image (encrypted for any Stegstr user)
stegstr-cli embed cover.png -o stego.png --payload @bundle.json --encrypt

# Recipient detects and extracts
stegstr-cli detect stego.png

Image format

PNG only (lossless). JPEG or other lossy formats will corrupt the hidden data.

Payload format

• Magic:

  STEGSTR

  (7 bytes ASCII)
• Length: 4 bytes, big-endian
• Payload: UTF-8 JSON or raw bytes (desktop app encrypts; CLI can embed raw or

  --encrypt

  )

Decrypted bundle:

{ "version": 1, "events": [ ... Nostr events ... ] }

. Schema: bundle.schema.json.

Links

• agents.txt: https://www.stegstr.com/agents.txt
• For agents: https://www.stegstr.com/wiki/for-agents.html
• CLI docs: https://www.stegstr.com/wiki/cli.html
• Downloads: https://github.com/brunkstr/Stegstr/releases/latest