ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Storing local data
Note: In addition to the encrypted local store, AIR also provides encryption for content stored in SQL databases. For
details, see “Using encryption with SQL databases” on page 757.
You may want to 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.
On desktop platforms, 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 128bit
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
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.
Because the user must be authenticated for these attacks to work, the user’s private data is still protected (unless the
user account itself is compromised). However, data that your application may want to keep secret from users, such as
keys used for licensing or digital rights management, is not secure. Thus 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 a 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.
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.
Last updated 6/6/2012
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