fix: emit EIP-55 checksummed addresses in SIWE messages

packages/reown_sign/lib/utils/address_utils.dart

@@ -1,3 +1,5 @@
+import 'package:wallet/wallet.dart' as wallet;
+
 class AddressUtils {
   static List<String> _getDidAddressSegments(String iss) {
     return iss.split(':');
@@ -43,9 +45,19 @@ class AddressUtils {
   }
 }
 
+final _evmAddress = RegExp(r'^(0x)?[0-9a-fA-F]{40}$');
+
 extension AddressUtilsExtension on String {
+  /// Checksums an EVM address per EIP-55. Non-EVM values are returned unchanged
+  /// so Solana / Bitcoin accounts are not forced through EthereumAddress.
   String toEIP55() {
-    return this;
-    // return EthereumAddress.fromHex(this).hexEip55;
+    if (!_evmAddress.hasMatch(this)) {
+      return this;
+    }
+    try {
+      return wallet.EthereumAddress.fromHex(this).eip55With0x;
+    } catch (_) {
+      return this;
+    }
   }
 }

packages/reown_sign/test/utils/address_utils_test.dart

@@ -21,5 +21,21 @@ void main() {
         TEST_ETHEREUM_CHAIN.split(':')[1],
       );
     });
+
+    test('toEIP55 checksums a lowercase EVM address', () {
+      expect(
+        '0x5aaeb6053f3e94c9b9a09f33669435e7ef1beaed'.toEIP55(),
+        '0x5aAeb6053F3E94C9b9A09f33669435E7Ef1BeAed',
+      );
+    });
+
+    test('toEIP55 keeps an already checksummed address', () {
+      expect(TEST_ADDRESS_EIP191.toEIP55(), TEST_ADDRESS_EIP191);
+    });
+
+    test('toEIP55 leaves non-EVM addresses unchanged', () {
+      const solana = '7EcDhSYGxXyscszYEp35KHN8vvw3svAuLKTzXwCFLtV';
+      expect(solana.toEIP55(), solana);
+    });
   });
 }