The skip-keychain framework is available at https://github.com/skiptools/skip-keychain.git, which can be checked out and tested with skip test once Skip is installed.

SkipKeychain

• Usage
• Backups
• Building
• Testing
• License

This is a Skip Swift/Kotlin library project providing a simple unified API to secure key/value storage. It uses the Keychain on Darwin platforms and EncyptedSharedPreferences on Android.

Usage

import SkipKeychain

let keychain = Keychain.shared

try keychain.set("value", forKey: "key")
assert(keychain.string(forKey: "key") == "value")

try keychain.removeValue(forKey: "key")
assert(keychain.string(forKey: "key") == nil)

Backups

Google recommends excluding encrypted shared preference files from backups to prevent restoring an encrypted file whose encryption key is lost. If your app targets devices running Android 11 or lower, follow the instructions here to create backup rules for your app and reference them from your AndroidManifest.xml. Your rules file should exclude SkipKeychain’s shared preferences, like so:

<?xml version="1.0" encoding="utf-8"?>
<full-backup-content>
    <exclude domain="sharedpref" path="tools.skip.SkipKeychain.xml"/>
</full-backup-content>

For newer devices, follow these instructions in addition to the steps above for older devices. Your additional rules file should contain the fllowing:

<?xml version="1.0" encoding="utf-8"?>
<data-extraction-rules>
  <cloud-backup>
    <exclude domain="sharedpref" path="tools.skip.SkipKeychain.xml"/>
  </cloud-backup>
  <device-transfer>
    <exclude domain="sharedpref" path="tools.skip.SkipKeychain.xml"/>
  </device-transfer>
</data-extraction-rules>

Building

This project is a Swift Package Manager module that uses the Skip plugin to transpile Swift into Kotlin.

Building the module requires that Skip be installed using Homebrew with brew install skiptools/skip/skip. This will also install the necessary build prerequisites: Kotlin, Gradle, and the Android build tools.

Testing

The module can be tested using the standard swift test command or by running the test target for the macOS destination in Xcode, which will run the Swift tests as well as the transpiled Kotlin JUnit tests in the Robolectric Android simulation environment.

Parity testing can be performed with skip test, which will output a table of the test results for both platforms.

License

This software is licensed under the GNU Lesser General Public License v3.0, with the following linking exception to clarify that distribution to restricted environments (e.g., app stores) is permitted:

This software is licensed under the LGPL3, included below. As a special exception to the GNU Lesser General Public License version 3 (“LGPL3”), the copyright holders of this Library give you permission to convey to a third party a Combined Work that links statically or dynamically to this Library without providing any Minimal Corresponding Source or Minimal Application Code as set out in 4d or providing the installation information set out in section 4e, provided that you comply with the other provisions of LGPL3 and provided that you meet, for the Application the terms and conditions of the license(s) which apply to the Application. Except as stated in this special exception, the provisions of LGPL3 will continue to comply in full to this Library. If you modify this Library, you may apply this exception to your version of this Library, but you are not obliged to do so. If you do not wish to do so, delete this exception statement from your version. This exception does not (and cannot) modify any license terms which apply to the Application, with which you must still comply.