Encode BIP137 SegWit message signature headers

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+- fixed: Encode BIP137 message signatures with the correct header byte for SegWit addresses (bip49 nested SegWit and bip84 native SegWit) and with each coin's own message prefix, so signatures verify on BIP137-compliant platforms across all UTXO currencies.
+
 ## 3.10.0 (2026-06-13)
 
 - changed: Convert the build tooling from Yarn to npm.

src/common/utxobased/engine/UtxoWalletTools.ts

@@ -241,7 +241,7 @@ export function makeUtxoWalletTools(
         path,
         xprivKeys
       })
-      return signMessageBase64(message, privKey)
+      return signMessageBase64(message, privKey, path.format, coin)
     }
   }
 

src/common/utxobased/keymanager/keymanager.ts

@@ -18,7 +18,13 @@ import { EdgeLog, EdgeMemo } from 'edge-core-js/types'
 
 import { indexAtProtected } from '../../../util/indexAtProtected'
 import { undefinedIfEmptyString } from '../../../util/undefinedIfEmptyString'
-import { ChangePath, CoinInfo, CoinPrefixes, FeeInfo } from '../../plugin/types'
+import {
+  ChangePath,
+  CoinInfo,
+  CoinPrefixes,
+  CurrencyFormat,
+  FeeInfo
+} from '../../plugin/types'
 import { UtxoData } from '../db/types'
 import { ScriptTemplate, ScriptTemplates } from '../info/scriptTemplates/types'
 import { sortInputs, sortOutputs } from './bip69'
@@ -938,14 +944,35 @@ export function privateKeyEncodingToPubkey(
   }).publicKey.toString('hex')
 }
 
-export function signMessageBase64(message: string, privateKey: string): string {
+export function signMessageBase64(
+  message: string,
+  privateKey: string,
+  format: CurrencyFormat,
+  coin: string
+): string {
   const ECPair = getECPair()
   const keyPair = ECPair.fromPrivateKey(Buffer.from(privateKey, 'hex'))
   if (keyPair.privateKey == null) {
     throw new Error('Address could not sign message')
   }
+  // BIP137 encodes the address type in the signature's header byte. Native
+  // SegWit (bip84 / P2WPKH) and nested SegWit (bip49 / P2SH-P2WPKH) each have
+  // their own header range; verifiers such as Bringin reject a SegWit address
+  // whose message was signed with a legacy (bip44) header byte.
+  const segwitType =
+    format === 'bip84'
+      ? 'p2wpkh'
+      : format === 'bip49'
+      ? 'p2sh(p2wpkh)'
+      : undefined
+  // Magic-hash the message with the coin's own prefix (e.g. "Litecoin Signed
+  // Message:\n") so the signature verifies against that coin's addresses.
+  // Every UTXO coin routes through here, not just Bitcoin.
+  const messagePrefix = getCoinFromString(coin).prefixes.messagePrefix[0]
   return bitcoinMessage
-    .sign(message, keyPair.privateKey, keyPair.compressed)
+    .sign(message, keyPair.privateKey, keyPair.compressed, messagePrefix, {
+      segwitType
+    })
     .toString('base64')
 }
 

test/common/utxobased/keymanager/coins/altcointestfixtures.ts

@@ -1,3 +1,4 @@
+import { CurrencyFormat } from '../../../../../src/common/plugin/types'
 import {
   AddressTypeEnum,
   BIP43PurposeTypeEnum,
@@ -45,6 +46,7 @@ interface XPubToPubkeyTests {
 interface SignMessageTests {
   wif: string
   message: string
+  format: CurrencyFormat
   signature: string
 }
 
@@ -842,6 +844,33 @@ export const fixtures: Fixture = {
           address: 'ltc1qjmxnz78nmc8nq77wuxh25n2es7rzm5c2rkk4wh',
           scriptPubkey: '001496cd3178f3de0f307bcee1aeaa4d5987862dd30a'
         }
+      ],
+      // Signatures use Litecoin's "Litecoin Signed Message:\n" prefix, so they
+      // differ from the Bitcoin vectors above for the same key/message and
+      // verify against Litecoin addresses. The leading base64 char (H/I/J)
+      // still encodes the BIP137 address type (legacy / p2sh-p2wpkh / p2wpkh).
+      signMessageTests: [
+        {
+          wif: 'L4rK1yDtCWekvXuE6oXD9jCYfFNV2cWRpVuPLBcCU2z8TrisoyY1',
+          message: 'This is an example of a signed message.',
+          format: 'bip44',
+          signature:
+            'H0UZW4iWKCquBbOO32dlUOkB8RqG81jJmfkMsvK8vppNDCFE5M17LvmtxQYHq6wcimb/LFk/urTz6VvbILtSth4='
+        },
+        {
+          wif: 'L4rK1yDtCWekvXuE6oXD9jCYfFNV2cWRpVuPLBcCU2z8TrisoyY1',
+          message: 'This is an example of a signed message.',
+          format: 'bip49',
+          signature:
+            'I0UZW4iWKCquBbOO32dlUOkB8RqG81jJmfkMsvK8vppNDCFE5M17LvmtxQYHq6wcimb/LFk/urTz6VvbILtSth4='
+        },
+        {
+          wif: 'L4rK1yDtCWekvXuE6oXD9jCYfFNV2cWRpVuPLBcCU2z8TrisoyY1',
+          message: 'This is an example of a signed message.',
+          format: 'bip84',
+          signature:
+            'J0UZW4iWKCquBbOO32dlUOkB8RqG81jJmfkMsvK8vppNDCFE5M17LvmtxQYHq6wcimb/LFk/urTz6VvbILtSth4='
+        }
       ]
     },
     {
@@ -1352,8 +1381,23 @@ export const fixtures: Fixture = {
         {
           wif: 'L4rK1yDtCWekvXuE6oXD9jCYfFNV2cWRpVuPLBcCU2z8TrisoyY1',
           message: 'This is an example of a signed message.',
+          format: 'bip44',
           signature:
             'H9L5yLFjti0QTHhPyFrZCT1V/MMnBtXKmoiKDZ78NDBjERki6ZTQZdSMCtkgoNmp17By9ItJr8o7ChX0XxY91nk='
+        },
+        {
+          wif: 'L4rK1yDtCWekvXuE6oXD9jCYfFNV2cWRpVuPLBcCU2z8TrisoyY1',
+          message: 'This is an example of a signed message.',
+          format: 'bip49',
+          signature:
+            'I9L5yLFjti0QTHhPyFrZCT1V/MMnBtXKmoiKDZ78NDBjERki6ZTQZdSMCtkgoNmp17By9ItJr8o7ChX0XxY91nk='
+        },
+        {
+          wif: 'L4rK1yDtCWekvXuE6oXD9jCYfFNV2cWRpVuPLBcCU2z8TrisoyY1',
+          message: 'This is an example of a signed message.',
+          format: 'bip84',
+          signature:
+            'J9L5yLFjti0QTHhPyFrZCT1V/MMnBtXKmoiKDZ78NDBjERki6ZTQZdSMCtkgoNmp17By9ItJr8o7ChX0XxY91nk='
         }
       ]
     },

test/common/utxobased/keymanager/coins/keymanagertest.spec.ts

@@ -130,12 +130,17 @@ describe('altcoin test fixtures', () => {
     }
     if (f.signMessageTests != null) {
       f.signMessageTests.forEach(j => {
-        it(`${f.name} sign message test`, () => {
+        it(`${f.name} sign message test (${j.format})`, () => {
           const privateKey = ECPair.fromWIF(j.wif).privateKey?.toString('hex')
           if (privateKey == null) {
             throw new Error('private key cannot be null')
           }
-          const signature = signMessageBase64(j.message, privateKey)
+          const signature = signMessageBase64(
+            j.message,
+            privateKey,
+            j.format,
+            f.name
+          )
           expect(signature).to.eqls(j.signature)
         })
       })