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Encrypt a Realm - React Native SDK

On this page

  • Considerations
  • Storing & Reusing Keys
  • Performance Impact
  • Encryption and Atlas Device Sync
  • Accessing an Encrypted Realm from Multiple Processes
  • Example

You can encrypt the realm database file on disk with AES-256 + SHA-2 by supplying a 64-byte encryption key when opening a realm.

Realm transparently encrypts and decrypts data with standard AES-256 encryption using the first 256 bits of the given 512-bit encryption key. Realm uses the other 256 bits of the 512-bit encryption key to validate integrity using a hash-based message authentication code (HMAC).


Do not use cryptographically-weak hashes for realm encryption keys. For optimal security, we recommend generating random rather than derived encryption keys.

The following are key impacts to consider when encrypting a realm.

You must pass the same encryption key every time you open the encrypted realm. If you don't provide a key or specify the wrong key for an encrypted realm, the Realm SDK throws an error.

Apps should store the encryption key securely, typically in the target platform's secure key/value storage, so that other apps cannot read the key.

Reads and writes on encrypted realms can be up to 10% slower than unencrypted realms.

You can encrypt a synced realm.

Realm only encrypts the data on the device and stores the data unencrypted in your Atlas data source. Any users with authorized access to the Atlas data source can read the data, but the following still applies:

  • Users must have the correct read permissions to read the synced data.

  • Data stored in Atlas is always encrypted at a volume (disk) level.

  • The transfer between client and server is always fully encrypted.

You can also enable Customer Key Management to encrypt stored Atlas data using your cloud provider's key (e.g. AWS KMS, Azure Key Vault, Google Cloud KMS).

If you need unique keys for each user of your application, you can use an OAuth provider or use one of the Realm authentication providers and an authentication trigger to create a 64-bit key and store that key in a user object.

Changed in version realm@11.8.0.

Starting with Realm React Native SDK version 11.8.0, Realm supports opening the same encrypted realm in multiple processes.

If your app uses Realm React Native SDK version 11.7.0 or earlier, attempting to open an encrypted realm from multiple processes throws this error: Encrypted interprocess sharing is currently unsupported.

The following code demonstrates how to generate an encryption key and open an encrypted realm:

import React from 'react';
import {createRealmContext, Realm} from '@realm/react';
import Cat from '../Models/Cat';
import {FlatList, View} from 'react-native';
// Retrieve key from secure location or create one...
const key = new Int8Array(64); // Populate with a secure key
// ... store key ...
const config: Realm.Configuration = {
schema: [Cat.schema],
// Add encryption key to realm configuration
encryptionKey: key,
path: + '.realm', // :remove
const {RealmProvider, useQuery} = createRealmContext(config);
function App() {
return (
<ListCats />
// Work with realm as normal once it's been opened.
function ListCats() {
const cats = useQuery<Cat>('Cat');
return (
renderItem={({item}) => <View>{}</View>}
keyExtractor={item =>}
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