spicebag 4.0.0

Visual Mnemonic Encoder / Decoder

Spicebag encodes cryptocurrency wallet seed phrases into color-coded PNG images and decodes them back. Each word in the mnemonic maps to a unique RGB color cell, producing a compact grid image that visually represents the seed, and can be optionally encrypted with a user-provided salt.

Features

• Encode a seed phrase into a single PNG image or bulk-generate multiple variants into a ZIP archive.

• Decode a color-coded PNG back into the original seed phrase.

• Salt-based encryption: an optional passphrase processed through Argon2id key derivation scatters each word's colors across the whole color space and shuffles the grid, making the image unreadable without the salt.

• Proof of phrase: every image carries an HMAC of its own phrase, so a wrong salt or an altered image is rejected instead of decoding to a different valid phrase.

• CLI mode: spicebag --encode, --decode and --palette run as plain prompts, without the full-screen TUI app.

• Multi-standard support:

  Standard	Word Counts	Wordlist Size
  BIP39	12, 15, 18, 21, 24	2048
  Electrum	12, 24	2048
  SLIP39	20, 33	1024

• PNG integrity checks: rejects images with forbidden chunks (e.g. PLTE, tRNS, iCCP) and verifies cell-level monochromatic consistency to detect lossy compression.

How It Works

1. Word → Index: Each seed word is looked up in its standard's wordlist.
2. Salt Keys: If a salt is provided, an Argon2id-derived master key is expanded via HKDF into a color key, a grid-shuffle key and a proof key.
3. Index → RGB: The word index fills the high bits of a 24-bit value and a block offset fills the low bits. The offset's top 3 bits carry a slice of the proof of phrase, an HMAC of the whole phrase under the proof key, and the rest is random. Without a salt, that value, split into R/G/B channels, is the cell's color. With a salt, a salt-keyed permutation first scatters it across the whole color space.
4. Grid Layout: Each color fills a square cell in a grid whose dimensions match the word count (e.g. 3×4 for 12 words, 4×6 for 24 words). When a salt is used, cell positions are deterministically shuffled.
5. Decoding: reverses all steps: undo the permutation, look up each word by index, and check the proof slices against the rebuilt phrase. A wrong salt fails the proof instead of decoding to a different valid phrase.

Manual Decoding

An image encoded without a salt can be decoded by hand, with nothing but a color picker and the wordlist. Manually decoding salted images is impossible.

1. Find the wordlist

Match the image's width-to-height ratio against the Aspect Ratio table to get the grid and word count. The word count decides the wordlist:

2. Read the cells in order

Words run left-to-right first, top-to-bottom, the same way you read most texts. Write down the hex code of each cell from the PNG file itself.

3. Turn each hex code into a word

The 16,777,216 colors from #000000 to #FFFFFF are split in order into equal chunks, one per word. The first word of the list owns the first chunk, the second word the next one, and so on:

Only red and green decide the word. Convert both to decimal (0 to 255), then:

⌊ ⌋ = rounded down. Blue is random filler and never changes the word. The word number is the line number in the wordlist file.

For example, a cell colored #65DFCD in a 24-word image has R = 0x65 = 101 and G = 0xDF = 223. That gives 101 × 8 + ⌊223 ÷ 32⌋ + 1 = 808 + 6 + 1 = 815, and line 815 of the BIP39 list is grape.

If a calculator is closer to hand, convert the whole hex code to decimal instead, divide by the colors per word from step 1, drop the remainder, and add 1: 0x65DFCD = 6,676,429, and ⌊6,676,429 ÷ 8,192⌋ + 1 = 815.

4. Check the phrase

The last word carries the phrase's checksum, so a misread cell almost always produces a phrase that fails validation.

Configuration Space

How many visually distinct images can encode the same seed phrase under the same salt?

Once the salt is fixed, almost everything is deterministic:

The block offset occupies the low bits of the 24-bit value left over after the word index is packed into the high bits. Its top 3 bits carry the proof of phrase, so the rest of it is the only free variable:

blockSize = 1 << (24 - (maxIdx.bit_length() - 1))

Every offset produces a distinct color: the offset fills the low bits of the 24-bit value, and the salted color permutation is a bijection, so no two offsets collide.

Since each grid holds exactly one cell per word, the total is (blockSize / 8) ^ wordCount:

Notes:

• Positions across salts: the layout dimension only opens up when the salt changes, contributing up to wordCount! arrangements (4.79 × 10⁸ for 12 words, 6.20 × 10²³ for 24). Within a single salt it collapses to one.
• Interactive preview: the clickable color-space editor rejects any color matching the cell's current color or an orthogonal neighbor, trimming at most 5 of 1,024 candidates per cell. The reduction is under 0.5%.
• No salt: the grid is left in natural reading order and no color permutation is applied, but the per-word color count is unchanged.

Valid PNG Requirements

To successfully decode, a PNG must pass all of the following checks:

Aspect Ratio

The image's width-to-height ratio determines the grid size and expected word count:

Image dimensions must be evenly divisible by their grid's column and row count (i.e. every cell must be the same whole-pixel size).

PNG Chunks

Validation is a blocklist, not an allowlist: any forbidden chunk causes immediate rejection, and every other chunk type passes. This ensures the image uses a direct RGB color model with no palette, transparency, or embedded ICC profile.

Color Mode

• RGB or RGBA with every alpha value at 255. Grayscale, palette and other color models are rejected, and so is an embedded color profile such as Adobe RGB.
• Other bit depths pass only if they read back as exactly the same 8-bit values.

Cell Integrity

Every pixel within a single grid cell must be exactly the same color. Any variation (e.g. from JPEG re-compression, anti-aliasing, or screenshot artifacts) will fail validation.

Requirements

• Python 3.10+
• A terminal with 24-bit color support. See Terminal

Terminal

The TUI app draws a full-screen interface and leans on four terminal capabilities. Each one degrades on its own, so a terminal missing some of them still runs the app:

Every terminal below covers all four. The versions listed are where the full set is reliably present, not the oldest build that runs the app at all.

On Windows, 1.18 is the release where Windows Terminal began answering palette queries. Earlier builds render identically but export screenshots against the fallback palette.

Known limitations. Spicebag still runs on all of these. They cost comfort, not function:

• macOS Terminal.app caps out at 256 colors, so gradients band and neighboring cells can render as the same color, which matters because cell colors carry the encoded data. It has no OSC 8 either, so saved files are not clickable. Use one of the macOS entries above instead.
• Windows legacy console host (conhost.exe) handles 24-bit color but answers no palette queries, so screenshots use the fallback, and it has no OSC 8, so saved files are not clickable. It also intercepts some control keys, which is why the screenshot shortcut is F12.
• tmux and screen hide palette queries from the terminal underneath and need explicit configuration for 24-bit color. Under tmux, set terminal-features for your terminal and enable allow-passthrough.

In the legacy console host, or in any terminal that does not advertise 24-bit color through COLORTERM, a notice under the header names the terminal and its version and recommends CLI mode, which needs none of the capabilities above.

Block glyphs (█ ▀ ▂ ░) and box-drawing characters are used throughout, so pick a monospace font that includes the Block Elements range. Cascadia Code, JetBrains Mono, Fira Code, and any Nerd Font patch all qualify.

Installation

pip install spicebag

This installs the spicebag command on your PATH. Run it with no arguments to open the TUI app, or with a flag such as --encode to use CLI mode.

If spicebag is not recognized after installing, pip placed it in a Scripts folder that is not on your PATH, which is common with the Microsoft Store Python and --user installs. python -m spicebag runs the same program without it, and pipx installs it with PATH handled for you: pipx install spicebag, then pipx ensurepath.

Windows executable

Every GitHub Release from 4.0.0 on carries a standalone spicebag.exe that needs no Python. Download it and run it from a terminal, as .\spicebag.exe or .\spicebag.exe --encode. It is not code-signed, so Windows SmartScreen may warn the first time it runs.

From source

Clone the repository, then let the launcher build the virtual environment for you:

git clone https://github.com/Enkhoder/Spicebag.git
cd Spicebag
run.bat

run.bat creates .venv/, installs requirements.txt, checks for missing dependencies, and launches the app.

To set it up on Linux and macOS, where run.bat does not apply:

python -m venv .venv
source .venv/bin/activate        # Windows: .venv\Scripts\activate
pip install -r requirements.txt
python -m spicebag

Run it from the repository root. pip install -e . instead installs the spicebag command against the checkout.

Usage

TUI app

Run with no arguments to open the full-screen interface:

spicebag            # installed via pip
run.bat             # from a source checkout on Windows

Type a command at the prompt:

Pressing ESC twice within a second at the menu also quits. An ESC less than half a second after the previous one never counts toward it, so a burst of ESC that steps back out of a flow or closes the help screen cannot quit by accident.

The encode flow prompts in order for image count, phrase, salt, salt confirmation, cell size, and save path. A single-image encode then shows a clickable color-space preview before writing the file.

CLI mode

Encode, decode and list cell colors straight from the shell, without opening the TUI app:

spicebag --encode   # or -e
spicebag --decode   # or -d
spicebag --palette  # or -p

Encode asks for the image count, seed phrase, salt, salt confirmation, cell size and save path. Decode asks for the image path and salt. Palette asks for the seed phrase, salt and cells. The seed phrase, the salt and its confirmation use native terminal masking, so nothing appears while you type. A rejected answer repeats the prompt with the reason in front of it.

Encode and decode then ask Proceed? (y/n) before doing any work. y or yes continues. n, no or three answers that are neither, plain ENTER included, end the run without writing anything. Case is ignored. Ctrl+C aborts at any step. Save paths follow the TUI app's rules, with ~ as your home folder, and spicebag --help lists them.

A decoded seed phrase is never printed. Decode reports what it recovered and asks before copying the phrase to the clipboard, so answering N checks an image and salt without exposing the phrase. On Windows the copy is kept out of clipboard history and cloud sync. macOS uses pbcopy and Linux uses wl-copy (Wayland), and neither can opt out of clipboard managers or Universal Clipboard, so clear the clipboard once you are done. Under WSL, the clipboard is mirrored to Windows and the mirror reads the phrase the moment it is offered, using up the one paste before you can make it, so decode and palette skip the copy question and report Clipboard unavailable for WSL. instead.

Palette lists every color each chosen cell can take for that phrase and salt, sorted ascending under headers like Cell [0][2] (row, then column, counted from 0), and asks before copying the list. Cells are row and column pairs, such as 0 2 3 1 for [0][2] and [3][1], and either index can be a range in either direction, so 0-2 1-2 covers rows 0 to 2 in columns 1 and 2. * or plain ENTER takes every cell, and a cell picked twice is copied once. The list gives away the seed phrase as surely as the phrase itself, so it is never printed and takes the same clipboard path as decode.

Output location

Images, ZIP archives, screenshots, and the banner preference file are written to ~/Spicebag/.

Security Considerations

• An unsalted image protects nothing. Anyone who gets hold of it can read the seed phrase back with a color picker and the public wordlist (see Manual Decoding). Treat it exactly like the phrase written on paper, and use a salt for any image you cannot keep physically secure.
• Salt is processed with Argon2id (time_cost=4, memory_cost=256 MiB), which makes every guess slow but cannot rescue a guessable salt. Use a long, random one.
• All randomness for color offsets uses Python's secrets module (CSPRNG).
• The salt is not stored anywhere. Losing it means the image cannot be decoded.

Bulk Generation

• A bulk encode builds every image at one pixel per cell first, and scales each one to the cell size only as it is written into the ZIP.
• The free bits of each cell's offset are drawn without replacement (secrets.SystemRandom().sample), so up to 1,024 images per archive (2,048 for SLIP39) never repeat a cell's color. Past that, cell colors can repeat, though two identical images remain vanishingly unlikely.
• PNGs are written with the fast compress_level=1, trading file size for speed at large cell sizes.

Contributing

docs/ARCHITECTURE.md maps the codebase layer-by-layer and documents the invariants that are not obvious from reading a single file, such as randomness source, single-sourced tables, and seed phrase handling in logs. Read it before changing anything in spicebag/backend/.

Trivia

This project was named after the iconic Irish-Chinese takeaway dish. You throw seasoning and salt into a paper bag and shake it. That's more or less what the encoder does.

License

This project is licensed under the MIT License.