Add wallet Sign Message flow for CEX ownership verification

[j0ntz]

CHANGELOG

Does this branch warrant an entry to the CHANGELOG?

• Yes
• No

Dependencies

none

Requirements

If you have made any visual changes to the GUI. Make sure you have:

• Tested on iOS device
• Tested on Android device
• Tested on small-screen device (iPod Touch)
• Tested on large-screen device (tablet)

Description

Adds an in-app Sign Message flow so a user can prove ownership of a self-hosted wallet by signing an exchange-provided message. This addresses EU Travel Rule / TFR withdrawal checks where CEXs/CASPs (Kraken, Coinbase, Bitvavo, Bitpanda, OKX, Bringin, NiceHash, etc.) require a signed message from the destination wallet instead of a manual ID/selfie proof.

BTC-first, per the task scope.

What it does

• Adds a Sign Message option to the wallet list menu, restricted to Bitcoin-family (UTXO) wallets whose plugin implements message signing.
• Opens a new SignMessageScene that shows the wallet's receive address (copyable, so the user can hand it to the exchange), a multiline message input, and a Sign Message button.
• Signs with wallet.signMessage(message, { otherParams: { publicAddress } }) and displays the resulting base64 signature in a copyable card.
• Includes a short phishing-safety note ("only sign messages from a service you trust; a signature never reveals your private keys").

Implementation notes

• signMessage is used rather than signBytes because for Bitcoin signBytes base64-re-encodes the bytes before signing, which would produce a signature over the wrong data. signMessage signs the literal UTF-8 message the exchange verifies (same pattern already used by bityProvider and EdgeProviderServer).
• The signing address is one the wallet owns (from wallet.getAddresses), because the UTXO plugin requires the address to be in its data layer.

Files

• SignMessageScene.tsx (new scene)
• routerTypes.tsx, Main.tsx (route + scene registration)
• WalletListMenuActions.tsx, WalletListMenuModal.tsx (menu entry, UTXO-scoped)
• en_US.ts (strings)

Asana: https://app.asana.com/0/1215088146871429/1209296431612665

Testing

Verified end-to-end on the iOS simulator (edge-funds, My Bitcoin wallet): opened the wallet menu, tapped Sign Message, entered a message, and confirmed a valid base64 signature was produced and displayed. Proof screenshots attached below.

---

Note

Medium Risk
Touches wallet signing and key-derived signatures for user-supplied messages; logic is scoped to owned addresses and includes BIP-137 edge-case handling, but phishing/mis-signing risk remains user-dependent.

Overview
Adds Sign Message to the wallet list menu for Bitcoin-family UTXO wallets, opening a new scene where users paste an exchange message, choose a signing address (default receive address or a specific owned address), and copy the resulting signature.

On SegWit chains (Bitcoin, Litecoin, DigiByte), users can pick Standard (Electrum) or BIP-137; new bitcoinMessageSignature helpers classify addresses, remap signature header bytes for native/nested SegWit, and block Taproot/P2WSH when BIP-137 is selected. Signing uses wallet.signMessage with publicAddress in otherParams, with UX guards (stale signature clearing, address-not-owned errors, safety copy).

Navigation, menu actions, locales, and unit tests for the BIP-137 utilities are included.

^{Reviewed by Cursor Bugbot for commit 752e288. Bugbot is set up for automated code reviews on this repo. Configure here.}

[j0ntz]

📸 Test evidence (iOS sim)

agent proof 1209296431612665 01 wallet menu sign message

agent proof 1209296431612665 02 sign message scene

agent proof 1209296431612665 03 signature success

Captured by the agent's in-app test run (build-and-test).

[j0ntz]

📸 Test evidence (after bugbot fixes)

agent proof 1209296431612665 04 segwit signature success

agent proof 1209296431612665 05 signature cleared on edit

Captured by the agent's in-app test run (build-and-test).

[j0ntz]

📸 Test evidence (followup: user-selectable signing address, Ravencoin UTXO wallet on iOS sim)

agent proof 1209296431612665 01 signmsg default address

agent proof 1209296431612665 02 signature default address

agent proof 1209296431612665 03 address edited signature cleared

agent proof 1209296431612665 04 signature after reset

Captured by the agent's in-app test run (build-and-test).

[j0ntz]

📸 Test evidence: BIP-137 signature format

agent proof 1209296431612665 01 format selector default

agent proof 1209296431612665 02 standard signature

agent proof 1209296431612665 03 bip137 signature

agent proof 1209296431612665 04 non segwit hidden

Captured by the agent's in-app test run (build-and-test).

[cursor]

Cursor Bugbot has reviewed your changes using default effort and found 1 potential issue.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 8870e5a. Configure here.}

[j0ntz]

📸 Test evidence (after Bugbot fixes): BIP-137 on HEAD + Taproot guard

agent proof 1209296431612665 01 format selector default

agent proof 1209296431612665 03 bip137 signature

agent proof 1209296431612665 04 non segwit hidden

agent proof 1209296431612665 05 taproot rejected

Captured by the agent's in-app test run (build-and-test).