feat(rn_cli_wallet): encrypt MMKV secret storage with keychain-backed key

wallets/rn_cli_wallet/package.json

@@ -69,6 +69,7 @@
     "expo-application": "~56.0.3",
     "expo-clipboard": "~56.0.4",
     "expo-navigation-bar": "~56.0.3",
+    "expo-secure-store": "~56.0.4",
     "expo-system-ui": "56.0.5",
     "lottie-react-native": "7.3.5",
     "pressto": "0.7.0",

wallets/rn_cli_wallet/src/utils/CantonWalletUtil.ts

@@ -72,7 +72,7 @@ export async function loadCantonWallet(input: string): Promise<{
   await storage.setItem('CANTON_SECRET_KEY_1', newWallet.getSecretKey());
   if (__DEV__) {
     console.warn(
-      '[SECURITY] Canton secret key stored unencrypted. Use secure enclave in production.',
+      '[SECURITY] Canton secret key stored in encrypted MMKV on native (key in Keychain/Keystore); unencrypted localStorage on web.',
     );
   }
 

wallets/rn_cli_wallet/src/utils/SolanaWalletUtil.ts

@@ -96,7 +96,7 @@ export async function loadSolanaWallet(input: string): Promise<{
 
   if (__DEV__) {
     console.warn(
-      '[SECURITY] Solana key material stored unencrypted. Use secure enclave in production.',
+      '[SECURITY] Solana key material stored in encrypted MMKV on native (key in Keychain/Keystore); unencrypted localStorage on web.',
     );
   }
 

wallets/rn_cli_wallet/src/utils/SuiWalletUtil.ts

@@ -64,7 +64,7 @@ export async function loadSuiWallet(input: string): Promise<{
   await storage.setItem('SUI_MNEMONIC_1', trimmedInput);
   if (__DEV__) {
     console.warn(
-      '[SECURITY] SUI mnemonic stored unencrypted. Use secure enclave in production.',
+      '[SECURITY] SUI mnemonic stored in encrypted MMKV on native (key in Keychain/Keystore); unencrypted localStorage on web.',
     );
   }
 

wallets/rn_cli_wallet/src/utils/TonWalletUtil.ts

@@ -79,7 +79,7 @@ export async function loadTonWallet(input: string): Promise<{
   await storage.setItem('TON_SECRET_KEY_1', newWallet.getSecretKey());
   if (__DEV__) {
     console.warn(
-      '[SECURITY] TON secret key stored unencrypted. Use secure enclave in production.',
+      '[SECURITY] TON secret key stored in encrypted MMKV on native (key in Keychain/Keystore); unencrypted localStorage on web.',
     );
   }
 

wallets/rn_cli_wallet/src/utils/TronWalletUtil.ts

@@ -68,7 +68,7 @@ export async function loadTronWallet(input: string): Promise<{
   storage.setItem('TRON_PrivateKey_1', trimmedInput);
   if (__DEV__) {
     console.warn(
-      '[SECURITY] TRON private key stored unencrypted. Use secure enclave in production.',
+      '[SECURITY] TRON private key stored in encrypted MMKV on native (key in Keychain/Keystore); unencrypted localStorage on web.',
     );
   }
 

wallets/rn_cli_wallet/src/utils/secureEncryptionKey.ts

@@ -0,0 +1,51 @@
+import { Platform } from 'react-native';
+import * as SecureStore from 'expo-secure-store';
+
+// Owns the lifecycle of the MMKV encryption key. The key is generated once and
+// persisted in the OS Keychain (iOS) / Keystore (Android) via expo-secure-store,
+// so the key that protects the wallet secrets never sits in plaintext MMKV.
+//
+// Native-only: SecureStore is unavailable on web, and the react-native-mmkv web
+// shim (localStorage) ignores encryption anyway — so on web we return undefined
+// and storage stays best-effort/unencrypted by design.
+
+const SECURE_STORE_KEY = 'mmkv_encryption_key';
+
+// MMKV's encryption key cannot exceed 16 bytes, so we generate 8 random bytes
+// and hex-encode them into a 16-character key.
+function generateKey(): string {
+  const bytes = crypto.getRandomValues(new Uint8Array(8));
+  return Array.from(bytes)
+    .map(b => b.toString(16).padStart(2, '0'))
+    .join('');
+}
+
+export interface EncryptionKeyResult {
+  // The MMKV encryption key, or undefined on web (no encryption available).
+  key: string | undefined;
+  // True when the key was just generated this launch — meaning an existing
+  // unencrypted MMKV store may need to be recrypted in place before use.
+  isNew: boolean;
+}
+
+let keyPromise: Promise<EncryptionKeyResult> | undefined;
+
+export function getEncryptionKey(): Promise<EncryptionKeyResult> {
+  if (!keyPromise) {
+    keyPromise = (async () => {
+      if (Platform.OS === 'web') {
+        return { key: undefined, isNew: false };
+      }
+
+      const existing = await SecureStore.getItemAsync(SECURE_STORE_KEY);
+      if (existing) {
+        return { key: existing, isNew: false };
+      }
+
+      const key = generateKey();
+      await SecureStore.setItemAsync(SECURE_STORE_KEY, key);
+      return { key, isNew: true };
+    })();
+  }
+  return keyPromise;
+}

wallets/rn_cli_wallet/src/utils/storage.ts

@@ -1,13 +1,56 @@
 import { MMKV } from 'react-native-mmkv';
 import { safeJsonParse, safeJsonStringify } from '@walletconnect/safe-json';
+import { getEncryptionKey } from './secureEncryptionKey';
 
-const mmkv = new MMKV();
+// The MMKV instance is created lazily because the encryption key must be
+// fetched from the OS Keychain/Keystore first (async). On native the store is
+// encrypted at rest; on web (no key) it falls back to the localStorage shim,
+// which is unencrypted by design.
+let mmkvPromise: Promise<MMKV> | undefined;
+
+function getStore(): Promise<MMKV> {
+  if (!mmkvPromise) {
+    mmkvPromise = (async () => {
+      const { key, isNew } = await getEncryptionKey();
+
+      if (!key) {
+        if (__DEV__) {
+          console.log('[storage] MMKV opened UNENCRYPTED (web / no key available)');
+        }
+        return new MMKV();
+      }
+
+      if (isNew) {
+        // Existing installs have an unencrypted default store on disk. Open it
+        // in plaintext, then encrypt it in place so previously stored wallet
+        // secrets survive the upgrade instead of appearing reset.
+        const instance = new MMKV();
+        instance.recrypt(key);
+        if (__DEV__) {
+          console.log(
+            '[storage] MMKV recrypted in place with new key (first run / plaintext→encrypted migration)',
+          );
+        }
+        return instance;
+      }
+
+      if (__DEV__) {
+        console.log('[storage] MMKV opened ENCRYPTED with existing key from SecureStore');
+      }
+      return new MMKV({ encryptionKey: key });
+    })();
+  }
+  return mmkvPromise;
+}
 
 export const storage = {
   getKeys: async () => {
+    const mmkv = await getStore();
     return mmkv.getAllKeys();
   },
   getEntries: async <T = any>(): Promise<[string, T][]> => {
+    const mmkv = await getStore();
+
     function parseEntry(key: string): [string, any] {
       const value = mmkv.getString(key);
       return [key, safeJsonParse(value ?? '')];
@@ -17,9 +60,11 @@ export const storage = {
     return keys.map(parseEntry);
   },
   setItem: async <T = any>(key: string, value: T) => {
+    const mmkv = await getStore();
     return mmkv.set(key, safeJsonStringify(value));
   },
   getItem: async <T = any>(key: string): Promise<T | undefined> => {
+    const mmkv = await getStore();
     const item = mmkv.getString(key);
     if (typeof item === 'undefined' || item === null) {
       return undefined;
@@ -28,6 +73,7 @@ export const storage = {
     return safeJsonParse(item) as T;
   },
   removeItem: async (key: string) => {
+    const mmkv = await getStore();
     return mmkv.delete(key);
   },
 };

wallets/rn_cli_wallet/yarn.lock

@@ -5256,6 +5256,7 @@ __metadata:
     expo-application: ~56.0.3
     expo-clipboard: ~56.0.4
     expo-navigation-bar: ~56.0.3
+    expo-secure-store: ~56.0.4
     expo-system-ui: 56.0.5
     jest: ^29.2.1
     jest-expo: 56.0.5
@@ -8387,6 +8388,15 @@ __metadata:
   languageName: node
   linkType: hard
 
+"expo-secure-store@npm:~56.0.4":
+  version: 56.0.4
+  resolution: "expo-secure-store@npm:56.0.4"
+  peerDependencies:
+    expo: "*"
+  checksum: a47a5c0378fdc7676df9d11b3f2417bac4106fcc9b7b461ee4774c8ffb0277a52e6c35545a0dff82de2f48dc9c112bd14060cc20a019cca1ea7507286a6822ac
+  languageName: node
+  linkType: hard
+
 "expo-server@npm:^56.0.5":
   version: 56.0.5
   resolution: "expo-server@npm:56.0.5"