[Cashtab] [xecjs-message upgrade p2/3] Sign msgs with ecash prefix in xecjs-message

Summary:
T2783

Depends on D12645

Sign msgs with ecash signature

Test Plan:
npm start
Sign a message
Confirm dev log displays 'Both methods not broken'
Verify a message
Confirm verification

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D12646

Author: BytesOfMan

web/cashtab/package-lock.json

@@ -92,7 +92,7 @@
         "webpack-manifest-plugin": "^4.0.2",
         "wif": "^2.0.6",
         "workbox-webpack-plugin": "^6.4.1",
-        "xecjs-message": "^1.0.5-b"
+        "xecjs-message": "^1.0.5-c"
     },
     "scripts": {
         "start": "node scripts/start.js",

web/cashtab/package.json

@@ -39,3 +39,7 @@
 **removed**
 
 -   All segwit support
+
+**added**
+
+-   Support for signing a message with standard eCash prefix

web/xecjs-message/CHANGELOG.md

@@ -36,7 +36,7 @@ function decodeSignature(buffer) {
 }
 
 function magicHash(message, messagePrefix) {
-    messagePrefix = messagePrefix || '\u0018Bitcoin Signed Message:\n';
+    messagePrefix = messagePrefix || '\u0016eCash Signed Message:\n';
     if (!Buffer.isBuffer(messagePrefix)) {
         messagePrefix = Buffer.from(messagePrefix, 'utf8');
     }
@@ -110,7 +110,11 @@ function verify(message, xecAddress, signature, messagePrefix) {
 
     const parsed = decodeSignature(signature);
 
-    const hashBitcoinSigned = magicHash(message, messagePrefix);
+    // Since Electrum ABC supports bitcoin signed messages, test for them by default
+    const hashBitcoinSigned = magicHash(
+        message,
+        '\u0018Bitcoin Signed Message:\n',
+    );
     const publicKeyBitcoinSigned = secp256k1.recover(
         hashBitcoinSigned,
         parsed.signature,
@@ -119,8 +123,8 @@ function verify(message, xecAddress, signature, messagePrefix) {
     );
     const publicKeyHashBitcoinSigned = hash160(publicKeyBitcoinSigned);
 
-    // Also test ecash: signed
-    const hashEcashSigned = magicHash(message, '\u0016eCash Signed Message:\n');
+    // Test for default eCash prefix or user specified prefix
+    const hashEcashSigned = magicHash(message, messagePrefix);
     const publicKeyEcashSigned = secp256k1.recover(
         hashEcashSigned,
         parsed.signature,
@@ -140,6 +144,10 @@ function verify(message, xecAddress, signature, messagePrefix) {
     expected = Buffer.alloc(decodedAddress.hash.length);
     expected.set(decodedAddress.hash);
 
+    if (bufferEquals(actualEcashSigned, expected)) {
+        console.log(`eCash signed message`);
+    }
+
     return (
         bufferEquals(actualEcashSigned, expected) ||
         bufferEquals(actualBitcoinSigned, expected)

web/xecjs-message/index.js

@@ -1,6 +1,6 @@
 {
     "name": "xecjs-message",
-    "version": "1.0.5b",
+    "version": "1.0.5c",
     "description": "xecjs-message",
     "keywords": [
         "xecjs-message",