Add BIP-137 signature format option to Sign Message

Let users on SegWit chains (Bitcoin, Litecoin, DigiByte) choose between the
Standard (Electrum) and BIP-137 signature formats. BIP-137 re-encodes the
signature header byte by address script type (native SegWit 39-42, nested
SegWit 35-38) so strict external verifiers recognize the address type. The
option is hidden on non-SegWit UTXO chains, and legacy addresses are never
remapped.

Author: j0ntz

CHANGELOG.md

@@ -2,7 +2,7 @@
 
 ## Unreleased (develop)
 
-- added: Sign Message option in the wallet list menu for Bitcoin-family wallets, letting users prove self-hosted wallet ownership to exchanges by signing an exchange-provided message from a chosen wallet address (defaulting to the current receive address, or a specific address the user enters).
+- added: Sign Message option in the wallet list menu for Bitcoin-family wallets, letting users prove self-hosted wallet ownership to exchanges by signing an exchange-provided message from a chosen wallet address (defaulting to the current receive address, or a specific address the user enters), and choosing between the Standard (Electrum) and BIP-137 signature formats on SegWit chains (Bitcoin, Litecoin, DigiByte).
 - added: Remote enable/disable of gift card providers via the info server's giftCardInfo config, supporting whole-provider disabling for Phaze and Bitrefill and per-brand disabling for Phaze.
 - changed: Reorganize the wallet list menu so Asset Settings is reached through Wallet Settings, and rename the Monero "Backend" card to "Server Settings".
 - fixed: Prevent imported Monero wallets from using the Edge LWS backend. Choosing to import now prompts the user to continue with a full node or configure a custom LWS server, matching the wallet settings rule.

src/__tests__/util/bitcoinMessageSignature.test.ts

@@ -0,0 +1,95 @@
+import { base64 } from 'rfc4648'
+
+import {
+  applyBip137Header,
+  getSegwitAddressType,
+  isBip137Supported
+} from '../../util/bitcoinMessageSignature'
+
+describe('bitcoinMessageSignature', () => {
+  describe('isBip137Supported', () => {
+    it('is true for SegWit UTXO chains', () => {
+      expect(isBip137Supported('bitcoin')).toBe(true)
+      expect(isBip137Supported('litecoin')).toBe(true)
+      expect(isBip137Supported('digibyte')).toBe(true)
+    })
+
+    it('is false for non-SegWit chains', () => {
+      expect(isBip137Supported('dogecoin')).toBe(false)
+      expect(isBip137Supported('bitcoincash')).toBe(false)
+      expect(isBip137Supported('dash')).toBe(false)
+    })
+  })
+
+  describe('getSegwitAddressType', () => {
+    it('classifies native SegWit addresses', () => {
+      expect(
+        getSegwitAddressType(
+          'bc1q8xcwww38eucj8d5zgzd8ymmameycs42xzh23qu',
+          'bitcoin'
+        )
+      ).toBe('p2wpkh')
+      expect(
+        getSegwitAddressType(
+          'ltc1qw508d6qejxtdg4y5r3zarvary0c5xw7kv8f3t4',
+          'litecoin'
+        )
+      ).toBe('p2wpkh')
+    })
+
+    it('classifies nested SegWit addresses', () => {
+      expect(
+        getSegwitAddressType('3J98t1WpEZ73CNmQviecrnyiWrnqRhWNLy', 'bitcoin')
+      ).toBe('p2sh-p2wpkh')
+      expect(
+        getSegwitAddressType('MLcbG7hUeXxTKfELi8fW9j2rTaGioLmt3H', 'litecoin')
+      ).toBe('p2sh-p2wpkh')
+    })
+
+    it('returns null for legacy addresses', () => {
+      expect(
+        getSegwitAddressType('1BvBMSEYstWetqTFn5Au4m4GFg7xJaNVN2', 'bitcoin')
+      ).toBeNull()
+    })
+
+    it('returns null for non-SegWit chains', () => {
+      expect(
+        getSegwitAddressType('DH5yaieqoZN36fDVciNyRueRGvGLR3mr7L', 'dogecoin')
+      ).toBeNull()
+    })
+  })
+
+  describe('applyBip137Header', () => {
+    // From the Asana task: the legacy signature for a native SegWit address
+    // starts with `I` (header byte 32, recovery id 1). BIP-137 native SegWit
+    // must land in the 39-42 range and start with `K`.
+    const legacyNativeSignature =
+      'ILDe+aXV9KBN3KIsoB68tMYiCbDzJtp2RBn3mpFzXPc1VG8jq2PbzWBS19lSaRFmEgmk2u7o2c69y5mlnKEhZEg='
+
+    it('remaps a native SegWit header into the 39-42 range', () => {
+      const result = applyBip137Header(legacyNativeSignature, 'p2wpkh')
+      expect(result.startsWith('K')).toBe(true)
+      expect(base64.parse(result)[0]).toBe(40)
+    })
+
+    it('remaps a nested SegWit header into the 35-38 range', () => {
+      const result = applyBip137Header(legacyNativeSignature, 'p2sh-p2wpkh')
+      expect(base64.parse(result)[0]).toBe(36)
+    })
+
+    it('preserves the r/s components, changing only the header byte', () => {
+      const original = base64.parse(legacyNativeSignature)
+      const remapped = base64.parse(
+        applyBip137Header(legacyNativeSignature, 'p2wpkh')
+      )
+      expect(remapped.slice(1)).toEqual(original.slice(1))
+    })
+
+    it('leaves a signature with an unexpected header untouched', () => {
+      const bytes = new Uint8Array(65)
+      bytes[0] = 20 // outside the legacy-compressed 31-34 range
+      const encoded = base64.stringify(bytes)
+      expect(applyBip137Header(encoded, 'p2wpkh')).toBe(encoded)
+    })
+  })
+})

src/components/scenes/SignMessageScene.tsx

@@ -6,6 +6,11 @@ import { View } from 'react-native'
 import { useHandler } from '../../hooks/useHandler'
 import { lstrings } from '../../locales/strings'
 import type { EdgeAppSceneProps } from '../../types/routerTypes'
+import {
+  applyBip137Header,
+  getSegwitAddressType,
+  isBip137Supported
+} from '../../util/bitcoinMessageSignature'
 import { SceneButtons } from '../buttons/SceneButtons'
 import { EdgeCard } from '../cards/EdgeCard'
 import { EdgeTouchableOpacity } from '../common/EdgeTouchableOpacity'
@@ -16,6 +21,7 @@ import { showError } from '../services/AirshipInstance'
 import { cacheStyles, type Theme, useTheme } from '../services/ThemeContext'
 import { EdgeText, Paragraph, SmallText } from '../themed/EdgeText'
 import { FilledTextInput } from '../themed/FilledTextInput'
+import { VectorIcon } from '../themed/VectorIcon'
 
 export interface SignMessageParams {
   walletId: string
@@ -25,6 +31,10 @@ interface Props extends EdgeAppSceneProps<'signMessage'> {
   wallet: EdgeCurrencyWallet
 }
 
+// The signature encoding the user picks. `standard` is the legacy Electrum
+// format the plugin emits; `bip137` re-encodes the header byte per BIP-137.
+type SignatureFormat = 'standard' | 'bip137'
+
 /**
  * Lets a user sign an arbitrary message with an address they control, to prove
  * self-hosted wallet ownership when withdrawing from a CEX/CASP (EU Travel
@@ -49,6 +59,13 @@ const SignMessageSceneComponent: React.FC<Props> = props => {
   const [message, setMessage] = React.useState('')
   const [signature, setSignature] = React.useState('')
   const [isSigning, setIsSigning] = React.useState(false)
+  const [sigFormat, setSigFormat] = React.useState<SignatureFormat>('standard')
+
+  // BIP-137 only maps SegWit script types, so the format choice is offered
+  // solely on chains that issue SegWit addresses (BTC, LTC, DGB). Other UTXO
+  // chains (Dogecoin, Bitcoin Cash, Dash) always sign in the standard format.
+  const { pluginId } = wallet.currencyInfo
+  const showFormatOptions = isBip137Supported(pluginId)
 
   // Default to the wallet's own receive address. Prefer the native segwit
   // address (the canonical receive address the user hands the exchange),
@@ -98,6 +115,18 @@ const SignMessageSceneComponent: React.FC<Props> = props => {
     setSignature('')
   })
 
+  // The signature is bound to the chosen format, so clear it when the format
+  // changes to prevent copying a signature in the wrong encoding.
+  const handleSelectStandardFormat = useHandler(() => {
+    setSigFormat('standard')
+    setSignature('')
+  })
+
+  const handleSelectBip137Format = useHandler(() => {
+    setSigFormat('bip137')
+    setSignature('')
+  })
+
   const handleSign = useHandler(async () => {
     if (address === '') {
       showError(lstrings.sign_message_no_address_error)
@@ -109,9 +138,20 @@ const SignMessageSceneComponent: React.FC<Props> = props => {
       // verify. `signBytes` would base64-re-encode the bytes before signing and
       // produce a signature over the wrong data, so it is not usable here.
       // eslint-disable-next-line @typescript-eslint/no-deprecated
-      const signedMessage = await wallet.signMessage(message, {
+      let signedMessage = await wallet.signMessage(message, {
         otherParams: { publicAddress: address }
       })
+
+      // The plugin emits the legacy Electrum format. When the user selects
+      // BIP-137 on a SegWit address, remap the header byte so strict verifiers
+      // recognize the script type. Legacy addresses are left unchanged, since
+      // BIP-137 does not alter their signatures.
+      if (sigFormat === 'bip137') {
+        const segwitType = getSegwitAddressType(address, pluginId)
+        if (segwitType != null) {
+          signedMessage = applyBip137Header(signedMessage, segwitType)
+        }
+      }
       setSignature(signedMessage)
     } catch (error: unknown) {
       // The plugin throws when the wallet does not own the address (or it is
@@ -177,6 +217,31 @@ const SignMessageSceneComponent: React.FC<Props> = props => {
           onChangeText={handleChangeMessage}
         />
 
+        {showFormatOptions ? (
+          <View style={styles.formatSection}>
+            <Paragraph>
+              <SmallText>{lstrings.sign_message_format_label}</SmallText>
+            </Paragraph>
+            <SignatureFormatRow
+              disabled={isSigning}
+              label={lstrings.sign_message_format_standard}
+              selected={sigFormat === 'standard'}
+              testID="signMessageFormatStandard"
+              onPress={handleSelectStandardFormat}
+            />
+            <SignatureFormatRow
+              disabled={isSigning}
+              label={lstrings.sign_message_format_bip137}
+              selected={sigFormat === 'bip137'}
+              testID="signMessageFormatBip137"
+              onPress={handleSelectBip137Format}
+            />
+            <Paragraph>
+              <SmallText>{lstrings.sign_message_format_helper}</SmallText>
+            </Paragraph>
+          </View>
+        ) : null}
+
         {signature !== '' && (
           <EdgeCard>
             <EdgeRow
@@ -205,6 +270,43 @@ const SignMessageSceneComponent: React.FC<Props> = props => {
   )
 }
 
+interface SignatureFormatRowProps {
+  disabled: boolean
+  label: string
+  selected: boolean
+  testID: string
+  onPress: () => void
+}
+
+/**
+ * A single radio option in the signature-format selector.
+ */
+const SignatureFormatRow: React.FC<SignatureFormatRowProps> = props => {
+  const { disabled, label, selected, testID, onPress } = props
+  const theme = useTheme()
+  const styles = getStyles(theme)
+
+  return (
+    <EdgeTouchableOpacity
+      style={styles.formatRow}
+      accessibilityRole="radio"
+      accessibilityState={{ selected }}
+      disabled={disabled}
+      testID={testID}
+      onPress={onPress}
+    >
+      <VectorIcon
+        font="Ionicons"
+        name={selected ? 'radio-button-on' : 'radio-button-off'}
+        size={theme.rem(1.25)}
+        color={theme.iconTappable}
+        style={styles.formatRadioIcon}
+      />
+      <EdgeText style={styles.formatRowLabel}>{label}</EdgeText>
+    </EdgeTouchableOpacity>
+  )
+}
+
 const getStyles = cacheStyles((theme: Theme) => ({
   container: {
     padding: theme.rem(0.5)
@@ -217,6 +319,21 @@ const getStyles = cacheStyles((theme: Theme) => ({
   useDefaultText: {
     color: theme.iconTappable,
     fontSize: theme.rem(0.75)
+  },
+  formatSection: {
+    paddingTop: theme.rem(0.5)
+  },
+  formatRow: {
+    flexDirection: 'row',
+    alignItems: 'center',
+    paddingHorizontal: theme.rem(0.5),
+    paddingVertical: theme.rem(0.5)
+  },
+  formatRadioIcon: {
+    marginRight: theme.rem(0.75)
+  },
+  formatRowLabel: {
+    flex: 1
   }
 }))
 

src/locales/en_US.ts

@@ -304,6 +304,11 @@ const strings = {
   sign_message_use_default_address: 'Use default address',
   sign_message_input_label: 'Message to Sign',
   sign_message_input_placeholder: 'Paste the message from the exchange',
+  sign_message_format_label: 'Signature Format',
+  sign_message_format_standard: 'Standard (Electrum)',
+  sign_message_format_bip137: 'BIP-137',
+  sign_message_format_helper:
+    'Most verifiers accept Standard (Electrum). Choose BIP-137 if an exchange requires the strict SegWit signature format.',
   sign_message_sign_button: 'Sign Message',
   sign_message_signature_label: 'Signature',
   sign_message_safety_note:

src/locales/strings/enUS.json

@@ -204,6 +204,10 @@
   "sign_message_use_default_address": "Use default address",
   "sign_message_input_label": "Message to Sign",
   "sign_message_input_placeholder": "Paste the message from the exchange",
+  "sign_message_format_label": "Signature Format",
+  "sign_message_format_standard": "Standard (Electrum)",
+  "sign_message_format_bip137": "BIP-137",
+  "sign_message_format_helper": "Most verifiers accept Standard (Electrum). Choose BIP-137 if an exchange requires the strict SegWit signature format.",
   "sign_message_sign_button": "Sign Message",
   "sign_message_signature_label": "Signature",
   "sign_message_safety_note": "Only sign messages from a service you trust. A signature proves you control this address but never reveals your private keys.",

src/util/bitcoinMessageSignature.ts

@@ -0,0 +1,86 @@
+import { base64 } from 'rfc4648'
+
+/**
+ * BIP-137 encodes the signing address' script type in the recoverable-signature
+ * header byte, so a verifier can derive the address type without being told it.
+ * The two SegWit variants:
+ *  - Native SegWit (P2WPKH, `bc1q…`): header 39-42 (Base64 prefix `K`/`L`)
+ *  - Nested SegWit (P2SH-P2WPKH, `3…`): header 35-38
+ * Legacy (P2PKH) addresses are not remapped by BIP-137.
+ */
+export type SegwitAddressType = 'p2wpkh' | 'p2sh-p2wpkh'
+
+interface SegwitChainInfo {
+  // The bech32 human-readable prefix of the chain's native SegWit addresses.
+  nativePrefix: string
+  // The base58 leading character(s) of the chain's nested-SegWit (P2SH) addresses.
+  nestedPrefixes: string[]
+}
+
+// Only chains that actually issue SegWit addresses can produce BIP-137
+// signatures. Non-SegWit UTXO chains (Dogecoin, Bitcoin Cash, Dash) are absent
+// on purpose, so the UI hides the format option for them.
+const SEGWIT_SIGN_CHAINS: Record<string, SegwitChainInfo> = {
+  bitcoin: { nativePrefix: 'bc1q', nestedPrefixes: ['3'] },
+  litecoin: { nativePrefix: 'ltc1q', nestedPrefixes: ['M', '3'] },
+  digibyte: { nativePrefix: 'dgb1q', nestedPrefixes: ['S'] }
+}
+
+// The signing plugin emits a compressed-key legacy header of `27 + 4 + recid`.
+// BIP-137 keeps the recovery id but shifts the base by the script type.
+const LEGACY_COMPRESSED_HEADER_BASE = 31
+const NESTED_SEGWIT_HEADER_BASE = 35
+const NATIVE_SEGWIT_HEADER_BASE = 39
+
+/**
+ * Whether the chain issues SegWit addresses, and therefore whether the BIP-137
+ * signature format is meaningful for it.
+ */
+export function isBip137Supported(pluginId: string): boolean {
+  return SEGWIT_SIGN_CHAINS[pluginId] != null
+}
+
+/**
+ * Classifies an owned address as native or nested SegWit for the given chain,
+ * or `null` when it is a legacy (or otherwise non-SegWit) address that BIP-137
+ * does not remap.
+ */
+export function getSegwitAddressType(
+  address: string,
+  pluginId: string
+): SegwitAddressType | null {
+  const chainInfo = SEGWIT_SIGN_CHAINS[pluginId]
+  if (chainInfo == null) return null
+
+  const trimmed = address.trim()
+  if (trimmed.toLowerCase().startsWith(chainInfo.nativePrefix)) {
+    return 'p2wpkh'
+  }
+  if (chainInfo.nestedPrefixes.some(prefix => trimmed.startsWith(prefix))) {
+    return 'p2sh-p2wpkh'
+  }
+  return null
+}
+
+/**
+ * Rewrites the header byte of a compact recoverable signature so it follows the
+ * BIP-137 encoding for the given SegWit script type. The r/s components are
+ * untouched, so the result verifies identically to a signature produced with
+ * the matching `segwitType`. Returns the input unchanged when the header is not
+ * the expected legacy-compressed byte.
+ */
+export function applyBip137Header(
+  signatureBase64: string,
+  segwitType: SegwitAddressType
+): string {
+  const bytes = base64.parse(signatureBase64)
+  const recoveryId = bytes[0] - LEGACY_COMPRESSED_HEADER_BASE
+  if (recoveryId < 0 || recoveryId > 3) return signatureBase64
+
+  const headerBase =
+    segwitType === 'p2wpkh'
+      ? NATIVE_SEGWIT_HEADER_BASE
+      : NESTED_SEGWIT_HEADER_BASE
+  bytes[0] = headerBase + recoveryId
+  return base64.stringify(bytes)
+}