AutistMask

AutistMask is a GPL-licensed JavaScript browser extension by @sneak that provides a minimal Ethereum wallet for Chrome and Firefox. It manages HD wallets derived from BIP-39 seed phrases and supports sending and receiving ETH and ERC-20 tokens, as well as web3 site connection and authentication via the EIP-1193 provider API.

Getting Started

git clone https://git.eeqj.de/sneak/autistmask.git
cd autistmask
make install
make build

Load the extension:

• Chrome: Navigate to chrome://extensions/, enable "Developer mode", click "Load unpacked", and select the dist/chrome/ directory.
• Firefox: Navigate to about:debugging#/runtime/this-firefox, click "Load Temporary Add-on", and select dist/firefox/manifest.json.

Rationale

MetaMask has become bloated with swap UIs, portfolio dashboards, analytics, tracking, and advertisements. It is no longer a simple wallet. Most alternatives (Rabby, Rainbow, etc.) only support Chromium browsers, leaving Firefox users without a usable option.

AutistMask exists to provide the absolute minimum viable Ethereum wallet experience: manage seed phrases, derive HD addresses, send and receive ETH and ERC-20 tokens, and connect to web3 sites. Nothing else. No swaps (that's what the web is for), no analytics, no tracking, no ads, no portfolio views, no NFT galleries. Just a wallet.

Design

AutistMask is a browser extension targeting both Chrome (Manifest V3) and Firefox (Manifest V2/V3 as supported). The codebase is shared between both targets with platform-specific manifest files and a build step that produces separate output directories.

Architecture

src/
  background/       — service worker / background script
    index.js        — extension lifecycle, message routing
    wallet.js       — wallet management (create, import, derive via ethers.js)
    provider.js     — EIP-1193 JSON-RPC provider implementation
  popup/            — popup UI (the main wallet interface)
    index.html
    index.js
    styles/         — CSS (Tailwind)
  content/          — content script injected into web pages
    index.js        — injects the provider into page context
    inpage.js       — the window.ethereum provider object
  shared/           — shared utilities
    vault.js        — encrypted storage via libsodium
    constants.js    — chain IDs, default RPC endpoints, ERC-20 ABI
manifest/
  chrome.json       — Manifest V3 for Chrome
  firefox.json      — Manifest V2/V3 for Firefox

UI Design Philosophy

The UI follows a "Universal Paperclips" aesthetic — a deliberately spartan, almost brutalist approach. The guiding principle is that an unskilled, non-technical person should be able to figure out how to use it without any crypto knowledge.

Visual Style

• Monochrome: Black text on white background. No brand colors, no gradients, no color-coding. Color may be introduced later for specific semantic purposes (e.g. error states) but the baseline is monochrome.
• Text-first: Every piece of information is presented as text. Balances are numbers. Addresses are hex strings. Status is a sentence. No progress spinners with animations — a text status line is sufficient.
• Monospace font: All text is rendered in the system monospace font. Ethereum addresses, transaction hashes, and balances are inherently fixed-width data. Rather than mixing proportional and monospace fonts, we use monospace everywhere for visual consistency and alignment.
• No images: Zero image assets in the entire extension. No logos, no illustrations, no token icons. Token identity is conveyed by symbol text (ETH, USDC, etc.).
• Tailwind CSS: Utility-first CSS via Tailwind. No custom CSS classes for styling. Tailwind is configured with a minimal monochrome palette. This keeps the styling co-located with the markup and eliminates CSS file management.
• Vanilla JS: No framework (React, Vue, Svelte, etc.). The popup UI is small enough that vanilla JS with simple view switching is sufficient. A framework would add bundle size, build complexity, and attack surface for no benefit at this scale.
• 360x600 popup: Standard browser extension popup dimensions. The UI is designed for this fixed viewport — no responsive breakpoints needed.

Language & Labeling

All user-facing text avoids crypto jargon wherever possible:

• "Recovery phrase" instead of "seed phrase", "mnemonic", or "BIP-39 mnemonic"
• "Address" instead of "account", "derived key", or "HD child"
• "Password" instead of "encryption key" or "vault passphrase"
• "Private key" instead of "secret key" or "signing key"
• Buttons use plain verbs: "Send", "Receive", "Copy address", "Add", "Back", "Cancel", "Lock", "Unlock", "Allow", "Deny"
• No bracket notation like [locked] or [setup] — just plain titles
• Helpful inline descriptions where needed (e.g. "This password locks the wallet on this device. It is not the same as your recovery phrase.")
• Error messages are full sentences ("Please enter your password." not "password required")

Full Identifiers Policy

Addresses, transaction hashes, contract addresses, and all other cryptographic identifiers are displayed in full whenever possible — never truncated. Address poisoning attacks exploit truncated displays by generating fraud addresses that share the same prefix and suffix as a legitimate address. If a user only sees 0xAbCd...1234, an attacker can create an address with the same visible characters and trick the user into sending funds to it. Showing the complete identifier defeats this class of attack. Truncation is only acceptable in space-constrained contexts where the full identifier is accessible one tap away (e.g. a tooltip or copy action).

Data Model

The core hierarchy is Wallets → Addresses:

• A wallet is either:
  • An HD wallet (recovery phrase): generates multiple addresses from a single 12/24 word recovery phrase using BIP-39/BIP-44 derivation. The user can add more addresses with a "+" button.
  • A key wallet (private key): a single address imported directly from a private key. No "+" button since there is only one address.
• An address holds ETH and any user-added ERC-20 tokens.
• The user can have multiple wallets, each with multiple addresses (HD) or a single address (key).

Navigation

The main view shows all addresses grouped by wallet, with ETH balances inline. The user taps an address to see its detail view (full address, balance, tokens, send/receive). Navigation is flat — every view has a "Back" or "Cancel" button that returns to the previous context. No deep nesting, no tabs, no hamburger menus.

UI Views

The popup has the following views, switched via simple show/hide:

1. Welcome: Shown on first use. Single "Add wallet" button.
2. Add wallet: A unified view for both creating and importing recovery phrase wallets. The recovery phrase text area starts empty. A clickable die button [die] generates a random 12-word phrase and fills it in. If the user already has a phrase, they paste it directly. When the die is clicked, a warning box appears reminding the user to write the phrase down. No password required — the xpub is derived and stored for read-only access.
3. Import private key: Paste a private key. This creates a wallet with a single address.
4. Main: All wallets listed, each showing its addresses (full, untruncated) and ETH balance. "+" next to recovery phrase wallets to add another address. "+ Add wallet" at the bottom. Settings button in the header. Future: a sub-heading showing total portfolio value in USD (and eventually other currencies).
5. Address detail: Full address (click to copy), ETH balance, USD value (future), Send/Receive buttons, token list with "+ Add" button.
6. Send: Token selector, recipient address, amount. Cancel returns to address detail.
7. Receive: Full address displayed with "Copy address" button.
8. Add token: Enter contract address. The extension looks up the token name/symbol automatically.
9. Settings: Network (RPC endpoint URL) with explanatory text.
10. Approval: When a website requests wallet access or a signature, shows the site origin, request details, and Allow/Deny buttons.

External Services

AutistMask is not a fully self-contained offline tool. It necessarily communicates with external services to function as a wallet:

• Ethereum JSON-RPC endpoint: The extension needs an Ethereum node to query balances (eth_getBalance), read ERC-20 token contracts (eth_call), estimate gas (eth_estimateGas), fetch nonces (eth_getTransactionCount), broadcast transactions (eth_sendRawTransaction), and check transaction receipts. The default endpoint is a public RPC (configurable by the user to any endpoint they prefer, including a local node). This is the only external service the extension talks to.

What the extension does NOT do:

• No analytics or telemetry services
• No token list APIs (user adds tokens manually by contract address)
• No price feed APIs (balances are shown in token units, not fiat)
• No phishing/blocklist APIs
• No Infura/Alchemy dependency (any JSON-RPC endpoint works)
• No backend servers operated by the developer

The user's RPC endpoint is the single point of external communication. Users who want maximum privacy can point it at their own Ethereum node.

Dependencies

AutistMask uses two runtime libraries. All cryptographic operations are delegated to these libraries — see the Crypto Policy section below.

Package	Version	License	Purpose
ethers	6.16.0	MIT	All Ethereum operations: BIP-39 mnemonic generation/validation, BIP-32/BIP-44 HD key derivation (m/44'/60'/0'/0/n), secp256k1 signing, transaction construction, ERC-20 contract interaction, JSON-RPC communication, address derivation (keccak256).
libsodium-wrappers-sumo	0.8.2	ISC	Password-based encryption of secrets at rest: Argon2id key derivation (crypto_pwhash), authenticated encryption (crypto_secretbox / XSalsa20-Poly1305).

Dev dependencies (not shipped in extension):

Package	Version	License	Purpose
esbuild	0.27.3	MIT	JS bundler (inlines deps)
tailwindcss	4.2.1	MIT	CSS compilation
@tailwindcss/cli	4.2.1	MIT	Tailwind CLI
jest	30.2.0	MIT	Test runner
prettier	3.8.1	MIT	Code formatter

Crypto Policy

No raw crypto primitives in application code. If the strings aes, sha, pbkdf, hmac, encrypt, decrypt, hash, cipher, digest, sign (case-insensitive) appear in our own source code (outside of node_modules/), it is almost certainly a bug. All cryptographic operations must go through ethers or libsodium-wrappers-sumo. This policy exists because:

• Rolling your own crypto is the single most common source of security vulnerabilities in wallet software.
• Both libraries are widely audited and battle-tested.
• Keeping crypto out of application code makes security review tractable: reviewers only need to verify that we call the libraries correctly, not that we implemented crypto correctly.

Exceptions require explicit authorization in a code comment referencing this policy.

DEBUG Mode Policy

The DEBUG constant in the popup JS enables a red "DEBUG / INSECURE" banner and a hardcoded test mnemonic. DEBUG mode must behave as close to normal mode as possible. No if (DEBUG) branches that skip functionality, bypass security flows, or alter program behavior beyond the banner and the hardcoded mnemonic. Adding new DEBUG-conditional branches requires explicit approval from the project owner.

Key Decisions

• No framework: The popup UI is vanilla JS and HTML. The extension is small enough that a framework adds unnecessary complexity and attack surface.
• Split storage model: Public data (xpubs, derived addresses, token lists, balances) is stored unencrypted in extension local storage so the user can view their wallets and balances at any time without entering a password. Private data (recovery phrases, private keys) will be encrypted at rest using libsodium — a password is only required when the user needs to sign a transaction or message. The encryption scheme for private data:
  • The user's password is run through Argon2id (crypto_pwhash) to derive a 256-bit encryption key. Argon2id is memory-hard, making GPU/ASIC brute force attacks expensive.
  • The derived key encrypts the secret material using XSalsa20-Poly1305 (crypto_secretbox), which provides authenticated encryption (the ciphertext cannot be tampered with without detection).
  • Stored blob: { salt, nonce, ciphertext } (the auth tag is part of the crypto_secretbox output).
  • The password is NOT used in address derivation. It exists solely to protect the recovery phrase / private key on disk. Anyone with the recovery phrase can restore the wallet on any device without this password. This matches MetaMask's behavior.
• BIP-39 / BIP-44 via ethers.js: Mnemonic generation, validation, and HD key derivation (m/44'/60'/0'/0/n) are handled entirely by ethers.js. The BIP-39 passphrase is always empty (matching MetaMask and most wallet software). The user's password is completely separate and has no effect on which addresses are generated.
• ethers.js for everything Ethereum: Transaction construction, signing, gas estimation, RPC communication, ERC-20 contract calls, and address derivation are all handled by ethers.js. This means zero hand-rolled Ethereum logic.
• EIP-1193 provider: The content script injects a window.ethereum object that implements the EIP-1193 provider interface, enabling web3 site connectivity.
• Minimal RPC: The extension communicates with Ethereum nodes via JSON-RPC through ethers.js's JsonRpcProvider. The default endpoint is configurable. No Infura dependency — users can point it at any Ethereum JSON-RPC endpoint.

Supported Functionality

• Create new HD wallet (generates 12-word recovery phrase)
• Import HD wallet from existing 12 or 24 word recovery phrase
• Import single-address wallet from private key
• Add multiple addresses within an HD wallet
• Manage multiple wallets simultaneously
• View ETH balance per address
• View ERC-20 token balances (user adds token by contract address)
• Send ETH to an address
• Send ERC-20 tokens to an address
• Receive ETH/tokens (display address, copy to clipboard)
• Connect to web3 sites (EIP-1193 eth_requestAccounts)
• Sign transactions requested by connected sites
• Sign messages (personal_sign, eth_sign)
• Lock/unlock with password
• Configurable RPC endpoint
• Future: USD value display (and other fiat currencies)

Non-Goals

• Token swaps (use a DEX in the browser)
• NFT display or management
• Multi-chain support (Ethereum mainnet only, for now)
• Analytics, telemetry, or tracking of any kind
• Advertisements or promotions
• Phishing detection
• Hardware wallet support (maybe later)
• Token list auto-discovery (user adds tokens manually)
• Fiat on/off ramps
• Browser notifications
• Transaction history (use Etherscan)

TODO

• Project scaffolding (Makefile, Dockerfile, CI, manifests)
• Set up Tailwind CSS build pipeline
• Build popup UI views (all 13 views with stub state)
• Implement BIP-39 mnemonic generation and validation
• Implement BIP-32/BIP-44 HD key derivation for Ethereum
• Implement private key import and address derivation
• Implement encrypted storage for wallet data
• Implement background wallet manager
• Implement EIP-1193 provider and content script injection
• Implement ETH balance lookup via RPC
• Implement ETH send (transaction construction + signing)
• Implement ERC-20 token management (add by contract, view balance, send)
• Implement site connection approval flow
• Implement transaction signing approval flow
• Implement message signing (personal_sign, eth_sign)
• Add USD value display (price feed TBD)
• Add multi-currency fiat display support
• Test on Chrome and Firefox
• Write tests for crypto operations
• Write tests for transaction construction
• Security audit of key management

License

GPL-3.0. See LICENSE.

Author

@sneak