EncryptedLocalStore  - AS3

Package	flash.data
Class	public class EncryptedLocalStore
Inheritance	EncryptedLocalStore Object

Language Version:

ActionScript 3.0

Runtime Versions:

AIR 1.0

The EncryptedLocalStore class (ELS) provides an encrypted local storage mechanism that can be used as a small cache for an application's private data.

ELS data cannot be shared between applications. The intent of ELS is to allow an application to store easily recreated items such as login credentials and other private information. ELS data should not be considered as permanent; see "Limitations of the encrypted local store" and "Best practices for using ELS." below.

AIR profile support: This feature is not supported on AIR for TV devices. You can test for support at run time using the EncryptedLocalStore.isSupported property. See AIR Profile Support for more information regarding API support across multiple profiles.

AIR provides an encrypted local store (ELS) for each AIR application installed on a user's computer or device. This lets you save and retrieve data that is stored on the user’s local hard drive in an encrypted format that cannot easily be deciphered by other users. A separate encrypted local store is used for each AIR application, and each AIR application uses a separate encrypted local store for each user account on the computer.

Use the encrypted local store to cache information that must be secured, such as login credentials for web services. The ELS is appropriate for storing information that must be kept private from other users. It does not, however, protect the data from other processes run under the same user account. It is thus not appropriate for protecting secret application data, such as DRM or encryption keys.

AIR uses DPAPI on Windows, KeyChain on Mac OS and iOS, and KeyRing or KWallet on Linux to associate the encrypted local store to each application and user. The encrypted local store uses AES-CBC 128-bit encryption.

On Android, the data stored by the EncryptedLocalStorage class are not encrypted. Instead the data is protected by the user-level security provided by the operating system. The Android operating system assigns every application a separate user ID. Applications can only access their own files and files created in public locations (such as the removable storage card). Note that on rooted Android devices, applications running with root privileges can access the files of other applications. Thus on a rooted device, the encrypted local store does not provide as high a level of data protection as it does on on a non-rooted device.

Information in the encrypted local store is only available to AIR application content in the application security sandbox.

If you update an AIR application, the updated version retains access to any existing data in the encrypted local store unless:

• The items were added with the stronglyBound parameter set to true
• You have upgraded from the AIR 3.2 namespace to AIR 3.3 (the physical location of the encrypted local store changed between AIR 3.2 and AIR 3.3 for both Mac OS and Windows)
• The existing and update versions are both published prior to AIR 1.5.3 and the update is signed with a migration signature

Limitations of the encrypted local store

The data in the encrypted local store is protected by the user’s operating system account credentials. Other entities cannot access the data in the store unless they can login as that user. However, the data is not secure against access by other applications run by an authenticated user. Thus, data that your application may want to keep secret from users, such as keys used for licensing or digital rights management, is not secure. The ELS is not an appropriate location for storing such information. It is only an appropriate place for storing a user’s private data, such as passwords.

Data in the ELS can be lost for a variety of reasons. For example, the user could uninstall the application and delete the encrypted file. Or, the publisher ID could be changed as a result of an update. Thus the ELS should be treated as a private cache, not permanent data storage.

The stronglyBound parameter is deprecated and should not be set to true. Setting the parameter to true does not provide any additional protection for data. At the same time, access to the data is lost whenever the application is updated — even if the publisher ID stays the same.

The encrypted local store may perform more slowly if the stored data exceeds 10MB.

When you uninstall an AIR application, the uninstaller does not delete data stored in the encrypted local store.

Best practices for using ELS

The best practices for using the ELS include:

• Use the ELS to store sensitive user data such as passwords (setting stronglyBound to false)
• Do not use the ELS to store applications secrets such as DRM keys or licensing tokens
• Provide a way for your application to recreate the data stored in the ELS if the ELS data is lost. For example, by prompting the user to re-enter their account credentials when necessary.
• Do not use the stronglyBound parameter.
• If you do set stronglyBound to true, do not migrate stored items during an update. Recreate the data after the update instead.
• Only store relatively small amounts of data. For large amounts of data, use an AIR SQL database with encryption.

Items in the encrypted local store are identified with a string. All items are stored as byte array data.

View the examples

More examples

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var str:String = "Bob";
var bytes:ByteArray = new ByteArray();
bytes.writeUTFBytes(str);
EncryptedLocalStore.setItem("firstName", bytes);

var storedValue:ByteArray = EncryptedLocalStore.getItem("firstName");
trace(storedValue.readUTFBytes(storedValue.length)); // "Bob"

EncryptedLocalStore.removeItem("firstName");