Posted by Oscar Rodriguez, Developer Relations Engineer
With the recent launch of the Play Integrity API, more developers are now taking action to protect their games and apps from potentially risky and fraudulent interactions.
In addition to useful signals on the integrity of the app, the integrity of the device, and licensing information, the Play Integrity API features a simple, yet very useful feature called “nonce” that, when correctly used, can further strengthen the existing protections the Play Integrity API offers, as well as mitigate certain types of attacks, such as person-in-the-middle (PITM) tampering attacks, and replay attacks.
In this blog post, we will take a deeper look at what the nonce is, how it works, and how it can be used to further protect your app.
In cryptography and security engineering, a nonce (number once) is a number that is used only once in a secure communication. There are many applications for nonces, such as in authentication, encryption and hashing.
In the Play Integrity API, the nonce is an opaque base-64 encoded binary blob that you set before invoking the API integrity check, and it will be returned as-is inside the signed response of the API. Depending on how you create and validate the nonce, it is possible to leverage it to further strengthen the existing protections the Play Integrity API offers, as well as mitigate certain types of attacks, such as person-in-the-middle (PITM) tampering attacks, and replay attacks.
Apart from returning the nonce as-is in the signed response, the Play Integrity API doesn’t perform any processing of the actual nonce data, so as long as it is a valid base-64 value, you can set any arbitrary value. That said, in order to digitally sign the response, the nonce is sent to Google’s servers, so it is very important not to set the nonce to any type of personally identifiable information (PII), such as the user’s name, phone or email address.
After having set up your app to use the Play Integrity API, you set the nonce with the setNonce() method, or its appropriate variant, available in the Kotlin, Java, Unity, and Native versions of the API.
setNonce()
Kotlin:
val nonce: String = ... // Create an instance of a manager. val integrityManager = IntegrityManagerFactory.create(applicationContext) // Request the integrity token by providing a nonce. val integrityTokenResponse: Task<IntegrityTokenResponse> = integrityManager.requestIntegrityToken( IntegrityTokenRequest.builder() .setNonce(nonce) // Set the nonce .build())
Java:
String nonce = ... // Create an instance of a manager. IntegrityManager integrityManager = IntegrityManagerFactory.create(getApplicationContext()); // Request the integrity token by providing a nonce. Task<IntegrityTokenResponse> integrityTokenResponse = integrityManager .requestIntegrityToken( IntegrityTokenRequest.builder() .setNonce(nonce) // Set the nonce .build());
Unity:
string nonce = ... // Create an instance of a manager. var integrityManager = new IntegrityManager(); // Request the integrity token by providing a nonce. var tokenRequest = new IntegrityTokenRequest(nonce); var requestIntegrityTokenOperation = integrityManager.RequestIntegrityToken(tokenRequest);
Native:
/// Create an IntegrityTokenRequest object. const char* nonce = ... IntegrityTokenRequest* request; IntegrityTokenRequest_create(&request); IntegrityTokenRequest_setNonce(request, nonce); // Set the nonce IntegrityTokenResponse* response; IntegrityErrorCode error_code = IntegrityManager_requestIntegrityToken(request, &response);
The response of the Play Integrity API is returned in the form of a JSON Web Token (JWT), whose payload is a plain-text JSON text, in the following format:
{ requestDetails: { ... } appIntegrity: { ... } deviceIntegrity: { ... } accountDetails: { ... } }
The nonce can be found inside the requestDetails structure, which is formatted in the following manner:
requestDetails
requestDetails: { requestPackageName: "...", nonce: "...", timestampMillis: ... }
The value of the nonce field should exactly match the one you previously passed to the API. Furthermore, since the nonce is inside the cryptographically signed response of the Play Integrity API, it is not feasible to alter its value after the response is received. It is by leveraging these properties that it is possible to use the nonce to further protect your app.
nonce
Let us consider the scenario in which a malicious user is interacting with an online game that reports the player score to the game server. In this case, the device is not compromised, but the user can view and modify the network data flow between the game and the server with the help of a proxy server or a VPN, so the malicious user can report a higher score, while the real score is much lower.
Simply calling the Play Integrity API is not sufficient to protect the app in this case: the device is not compromised, and the app is legitimate, so all the checks done by the Play Integrity API will pass.
However, it is possible to leverage the nonce of the Play Integrity API to protect this particular high-value operation of reporting the game score, by encoding the value of the operation inside the nonce. The implementation is as follows:
The following sequence diagram illustrates these steps:
As long as the original message to protect is sent along with the signed result, and both the server and client use the exact same mechanism for calculating the nonce, this offers a strong guarantee that the message has not been tampered with.
Notice that in this scenario, the security model works under the assumption that the attack is happening in the network, not the device or the app, so it is particularly important to also verify the device and app integrity signals that the Play Integrity API offers as well.
Let us consider another scenario in which a malicious user is trying to interact with a server-client app protected by the Play Integrity API, but wants to do so with a compromised device, in a way so the server doesn’t detect this.
To do so, the attacker first uses the app with a legitimate device, and gathers the signed response of the Play Integrity API. The attacker then uses the app with the compromised device, intercepts the Play Integrity API call, and instead of performing the integrity checks, it simply returns the previously recorded signed response.
Since the signed response has not been altered in any way, the digital signature will look okay, and the app server may be fooled into thinking it is communicating with a legitimate device. This is called a replay attack.
The first line of defense against such an attack is to verify the timestampMillis field in the signed response. This field contains the timestamp when the response was created, and can be useful in detecting suspiciously old responses, even when the digital signature is verified as authentic.
timestampMillis
That said, it is also possible to leverage the nonce in the Play Integrity API, to assign a unique value to each response, and verifying that the response matches the previously set unique value. The implementation is as follows:
With this implementation, each time the server asks the app to call the Play Integrity API, it does so with a different globally unique value, so as long as this value cannot be predicted by the attacker, it is not possible to reuse a previous response, as the nonce won’t match the expected value.
While the two mechanisms described above work in very different ways, if an app requires both protections at the same time, it is possible to combine them in a single Play Integrity API call, for example, by appending the results of both protections into a larger base-64 nonce. An implementation that combines both approaches is as follows:
These are some examples of ways you can use the nonce to further protect your app against malicious users. If your app handles sensitive data, or is vulnerable against abuse, we hope you consider taking action to mitigate these threats with the help of the Play Integrity API.
To learn more about using the Play Integrity API and to get started, visit the documentation at g.co/play/integrityapi.
Since 2007, Airbnb has grown to connect more than 4 million hosts with more than 1 billion guests across the globe. One of the reasons behind the app’s success is that its developers aim to achieve engineering excellence by focusing on two main principles: using technology that sparks innovative development and empowering the engineers behind the work.
Jetpack Compose, Android’s modern UI-building toolkit, directly supports both of Airbnb’s development principles. Compose provided a solid foundation for adaptable, quality engineering and reduced boilerplate code, so developers could focus on delivering a great user experience — and advance their two-fold pursuit of engineering excellence.
Airbnb started testing Compose in 2020 when it was in developer preview. As an early adopter, the Airbnb team was eager use the various new features and simplify their workflow. Now, having gained confidence using Compose in production, Airbnb engineers continue to be satisfied with how it improved their development process.
Compose’s deterministic testing helped ensure Airbnb’s engineers had tight control over the UI tests they ran and eliminated common flakiness, thereby strengthening their confidence in the quality of every part of their app and the user experiences they were creating. Engineers can now also use Compose to test animations they previously couldn't.
Similarly, Airbnb developers used Compose to add automated screenshot tests to their codebase. Because they didn’t need to write the code for screenshot testing, engineers could go straight into using it to catch bugs and regressions. This gave them more time to review and guarantee feature functionality and UI appearance across a variety of devices.
Compose is great to use alongside Views. This interoperability made it easy for Airbnb engineers to onboard and test the new UI toolkit at their own pace, so they were able to experience the benefits of Compose without having to migrate entire features.
These engineering improvements gave them the solid technical foundations they needed to serve users in fresh and improved ways.
Airbnb keeps hosts and guests at the heart of their decisions. The engineering team was excited to adopt Compose when they learned about how it would enable them to more easily and efficiently produce UI, resulting in better experiences for their end users.
Because Compose made Airbnb’s features require significantly less code to write and manage, the Airbnb team boosted their efficiency. All of this meant the team could focus its energy on executing the complex tasks involved in developing the innovative features that could best serve users.
Because their features now require less code, the Airbnb team will be able to slow the growth of their app size in the long run. Providing a smaller app is important to Airbnb as an organization with users across the globe that looks to ensure all hosts and guests can easily download and access their app — especially those with older devices or logging on from countries with high data costs.
Using Compose’s engineering enhancements, the Airbnb team was able to put user needs first.
Compose simplified UI development to allow Airbnb engineers the freedom to focus on more dynamic and innovative features that benefit the app’s hosts and guests.
Learn how you can improve your team’s productivity with Jetpack Compose.
Posted by Paris Hsu, Product & Design, Android and Don Turner, Developer Relations Engineer, Android
The Now in Android app is now on GitHub!
For two years, 'Now in Android' has been a popular blog and YouTube series, providing you with the latest and greatest developer news from the Android team. Starting today, you can check out the alpha version of the Now in Android app on GitHub! 🎉
The app has two goals:
Firstly, it showcases best practices, opinionated designs, and solutions to complex real-world problems which other sample apps don’t handle. It does so with an open source implementation of a real world app.
Secondly, it helps you (the developer) keep up to date with the areas of Android development which interest you most. It is a working app planned for publication on the Play Store.
Now in Android app screen designs
For this first alpha release, the Now in Android app includes:
As well as these features, we are also documenting the learning journeys we took to certain decisions with the app's design and implementation. Check out our first journey on the app's Architecture here.
The Now in Android screens adapt based on device screen size
Since this is an alpha release, we expect that there will be bugs and missing features, and we would greatly appreciate your feedback. We have some exciting features planned, such as user authentication and loading data from a real backend. We can’t wait for you to check out the app and let us know what you think!
Finally, if you want to learn about the tools we used to build the app and how we target multiple screen sizes, check out these talks from this year's Google I/O:
Shobana Radhakrishnan, Senior Director of Engineering - Google TV
Paul Lammertsma, Developer Relations Engineer
Today, there is more entertainment content available than ever before. In fact, our research shows a third of U.S. households now watch more than 25 hours of TV every week. As the role of TV continues to evolve, it’s our goal to build a tailored TV experience that gives users easy access to the entertainment they love.
We’re excited about the future of Android TV OS, now with over 110 million monthly active devices, including millions of Google TVs. Android TV and Google TV are available on over 300 partners worldwide, including 7 of the 10 largest smart TV OEMs and over 170 pay TV operators. And thanks to the hard work of our developer community, there are more than 10,000 apps available on TV, with more being added everyday.
Since last year’s I/O, we’ve continued our commitment to enable you to build better and more engaging experiences on Android TV OS. In addition to platform updates, new features, like expanded integrations with the Live tab, offer opportunities for users to better engage with your content. And if you haven’t begun using WatchNext API, take a moment to learn how to add it to your app to make your content more discoverable and accessible.
Today, we are introducing new features and tools on Android 13 that focus on overall performance & quality, improve accessibility, and enable multitasking.
Android 13 Beta for TV is available now, allowing you to test your apps and provide feedback on the latest release. Thank you for your continued support of Android TV OS. We can’t wait to see what amazing and innovative things you continue to build for the big screen.
Posted by Jennifer Chui, Technical Program Manager and Rod Lopez, Product Manager
At Google, our work in cars has always been guided by our vision of creating safe and seamless connected experiences. This work would not be possible without developers like you. We’re excited to share some of our combined accomplishments from this past year, and introduce new updates that will make it easier for you to provide users with an even better experience in the car.
Android Auto continues to grow and scale, with compatible vehicles now numbering over 150 million worldwide. An increasing number are also wirelessly compatible, and with the newly introduced Motorola MA1 adapter, even more drivers now have access to a wireless experience. In addition, our new design for Android Auto brings split-screen functionality to every screen, keeping navigation and media front and center while also providing room for prominent notification widgets.
Android Automotive OS with Google built-in also has exciting updates. Beyond the continued expansion of carmakers that are bringing more car models to the market, we’ve also been hard at work enabling more parked experiences to take advantage of the large screens that many AAOS cars offer. From more video streaming apps like Epix Now and Tubi to future features like browsing and cast, there’s much to look forward to, and given minimal effort is required to translate your large screen tablet apps into a parked car experience, it’s now easier than ever to reach users in the car.
We know that developing for cars can be complex, which is why we’re focused on making developing across Android for Cars as easy as possible. We’ve seen strong momentum with our Car App Library with over 200 apps published to date, and beyond enriching the navigation feature set with version 1.3, we’re also excited to share that all developers can now publish apps in supported categories directly to production for both Android Auto and Android Automotive OS. We’ve also created new templates and expanded our supported app categories, adding driver apps like Lyft to the navigation category, and replacing the parking and charging categories with a comprehensive point of interest (POI) category to include apps like MochiMochi and Fuelio.
We’re also introducing several new features to help you build more powerful media apps on Android Auto. Media recommendations working side by side with Google Assistant helps users easily discover and quickly play relevant content based on their preferred music provider at the click of a button. To surface recommendations from your app, integrate with this API.
For long form content such as podcasts and audiobooks, you can now introduce a progress bar that shows how much of the content the user has previously listened to, and with our new single item styling API, you can now assign content items individually as either list or grid as opposed to categorically, to easily combine them in the same content space.
We’re grateful to have you on the journey with us as we seek to create safer, more seamless connected experiences in cars. Be sure to check out our Google I/O technical session above, and as always, you can get help from the developer community at Stack Overflow using the android-automotive and android-auto tags. We can’t wait to see what you build next, and where the road takes you.
Posted by Maru Ahues Bouza, Director of Android Developer Relations
There aren’t many platforms where you can build something and instantly reach billions of people around the world, not only on their phones—but their TVs, cars, tablets, watches, and more. Today, at Google I/O, we covered a number of ways Android helps you make the most of this opportunity, and how Modern Android Development brings as much commonality as possible, to make it faster and easier for you to create experiences that tailor to all the different screens we use in our daily lives.
We’ve rounded up the top 13 things to know for Android developers—from Jetpack Compose to tablets to Wear OS and of course… Android 13! And stick around for Day 2 of Google I/O, when Android’s full track of 26 technical talks and 4 workshops drop. We’re also bringing back the Android fireside Q&A in another episode of #TheAndroidShow; tweet us your questions now using #AskAndroid, and we’ve assembled a team of experts to answer live on-air, May 12 at 12:30PM PT.
Android’s modern UI toolkit, Jetpack Compose, continues to bring the APIs you need to support more advanced use cases like downloadable fonts, LazyGrids, window insets, nested scrolling interop and more tooling support with features like LiveEdit, Recomposition Debugging and Animation Preview. Check out the blog post for more details.
Get more done faster with Android Studio Dolphin Beta and Electric Eel Canary! Android Studio Dolphin includes new features and improvements for Jetpack Compose and Wear OS development and an updated Logcat experience. Android Studio Electric Eel comes with integrations with the new Google Play SDK Index and Firebase Crashlytics. It also offers a new resizable emulator to test your app on large screens and the new Live Edit feature to immediately deploy code changes made within composable functions. Watch the What’s new in Android Development Tools session and read the Android Studio I/O blog post here.
The speed of your app right after installation can make a big difference on user retention. To improve that experience, we created Baseline Profiles. Baseline Profiles allow apps and libraries to provide the Android runtime with metadata about code path usage, which it uses to prioritize ahead-of-time compilation. We've seen up to 30% faster app startup times thanks to adding baseline profiles alone, no other code changes required! We’re already using baseline profiles within Jetpack: we’ve added baselines to popular libraries like Fragments and Compose – to help provide a better end-user experience. Watch the What’s new in app performance talk, and read the Jetpack blog post here.
Google is all in on tablets. Since last I/O we launched Android 12L, a release focused on large screen optimizations, and Android 13 includes all those improvements and more. We also announced the Pixel tablet, coming next year. With amazing new hardware, an updated operating system & Google apps, improved guidelines and libraries, and exciting changes to the Play store, there has never been a better time to review your apps and get them ready for large screens and Android 13. That’s why at this year’s I/O we have four talks and a workshop to take you from design to implementation for large screens.
With the latest updates to Wear OS, you can rethink what is possible when developing for wearables. Jetpack Compose for Wear OS is now in beta, so you can create beautiful Wear OS apps with fewer lines of code. Health Services is also now in beta, bringing a ton of innovation to the health and fitness developer community. And last, but certainly not least, we announced the launch of The Google Pixel Watch - coming this Fall - which brings together the best of Fitbit and Wear OS. You can learn more about all the most exciting updates for wearables by watching the Wear OS technical session and reading our Jetpack Compose for Wear OS announcement.
Health Connect is a new platform built in close collaboration between Google and Samsung, that simplifies connectivity between apps making it easier to reach more users with less work, so you can securely access and share user health and fitness data across apps and devices. Today, we’re opening up access to Health Connect through Jetpack Health—read our announcement or watch the I/O session to find out more!
Android for Cars and Android TV OS continue to grow in the US and abroad. As more users drive connected or tune-in, we’re introducing new features to make it even easier to develop apps for cars and TV this year. Catch the “What’s new with Android for Cars” and “What's new with Google TV and Android TV” sessions on Day 2 (May 12th) at 9:00 AM PT to learn more.
We’re making it easier for users to access your apps via voice across devices with Google Assistant, by expanding developer access to Shortcuts API for Android for Cars, with support for Wear OS apps coming later this year. We’re also making it easier to build those experiences with Smarter Custom Intents, enabling Assistant to better detect broader instances of user queries through ML, without any NLU training heavy lift. Additionally, we’re introducing improvements that drive discovery to your apps via voice on Mobile, first through Brandless Queries, that drive app usage even when the user hasn’t explicitly said your app’s name, and App Install Suggestions that appear if your isn’t installed yet–these are automatically enabled for existing App Actions today.
Get the latest updates from Google Play, including new ways Play can help you grow your business. Highlights include the ability to deep-link and create up to 50 custom listings; our LiveOps beta, which will allow more developers to submit content to be considered for featuring on the Play Store; and even more flexibility in selling subscriptions. Learn about these updates and more in our blog post.
Evaluate if an SDK is right for your app with the new Google Play SDK index. This new public portal lists over 100 of the most widely used commercial SDKs and information like which app permissions the SDK requests, statistics on the apps that use them, and which version of the SDK is most popular. Learn more on our blog post and watch “What’s new in Google Play” and “What’s new in Android development tools” sessions.
Privacy Sandbox on Android provides a path for new advertising solutions to improve user privacy without putting access to free content and services at risk. We recently released the first Privacy Sandbox on Android Developer Preview so you can get an early look at the SDK Runtime and Topics API. You can conduct preliminary testing of these new technologies, evaluate how you might adopt them for your solutions, and share feedback with us. Learn more in the "Overview of the Privacy Sandbox in Android" session.
The new Google Wallet gives users fast and secure access to everyday essentials across Android and Wear OS. We’re enhancing the Google Wallet API, previously called Google Pay Passes API, to support generic passes, grouping and mixing passes together, for example grouping an event ticket with a voucher, and launching a new Android SDK which allows you to save passes directly from your app without a backend integration. To learn more, read the full blog post, watch the session, or read the docs at developers.google.com/wallet.
The second Beta of Android 13 is available today! Get your apps ready for the latest features for privacy and security, like the new notification permission, the privacy-protecting photo picker, and improved permissions for pairing with nearby devices and accessing media files. Enhance your app with features like app-specific language support and themed app icons. Build with modern standards like HDR video and Bluetooth LE Audio. You can get started by enrolling your Pixel device here, or try Android 13 Beta on select phones, tablets, and foldables from our partners - visit developer.android.com/13 to learn more.
That’s just a snapshot of some of the highlights for Android developers at this year’s Google I/O. Be sure to watch the What’s New in Android talk to get the landscape on the full Android technical track at Google I/O, which includes 26 talks and 4 workshops. Enjoy!
Posted by Kseniia Shumelchyk, Developer Relations Engineer, and John Nichol, Tech Lead of Compose for Wear OS
Today we’re launching the Beta release of Compose for Wear OS, our modern declarative UI toolkit designed to help developers create beautiful user experiences for Wear OS.
Compose for Wear OS adds support for watch optimized components that embrace the latest Material design for Wear OS. The components are built on top of core Compose libraries and the toolkit leverages Modern Android Development, helping accelerate the development process as a whole.
With this Beta release, Compose for Wear OS is feature complete for the 1.0 release coming later this year, and has what you need to build production-ready apps. It also means the API is stable; moving forward we'll focus on performance and polishing existing components for the 1.0 release.
We’ve been hard at work since last I/O to bring the best of Jetpack Compose to Wear OS, engaging with the community via Slack, gathering developer feedback on APIs, components and tooling. As a result, we’ve improved a number of components such as navigation, scaling lazy lists, input and gesture support and much more.
The first Beta release follows 21 alpha releases. The major changes since the Developer Preview announcement include:
You asked for user input components, so we’ve added different composables that you can tailor for your watch app:
We’ve added full-screen Alert and Confirmation composables that can be used as either navigation destinations or traditional full-screen Dialogs, which will be layered over any other content. Dialog supports swipe-to-dismiss and will reveal the parent content in the background during the swipe gesture.
For consistency with Scaffold, a full-screen dialog displays a PositionIndicator and a Vignette.
We added CircularProgressIndicator, a progress indicator optimized for watch screens to display progress by animating an indicator along a circular track in a clockwise direction.
There are several options for how CircularProgressIndicator can be used: either to show infinite progress or to express the proportion of completion of an ongoing task. Progress Indicators allow a gap in the circular track which leaves room for other content, for instance TimeText if used in full-screen.
To help you implement pagination, the UI toolkit provides a HorizontalPageIndicator component that represents the total number of pages and selected page.
Depending on the screen shape, the HorizontalPageIndicator will provide a form factor- specific visual indication of which page is active and how far through the pages it is.
With these recent additions, the Compose Material catalog for Wear OS now has more components than are available with View-based layouts and provides out-of-the-box implementation of the new Wear OS design guidelines.
Android Studio Electric Eel provides the latest features for the best experience developing with Compose for Wear OS:
Today we’re also announcing the release of Horologist, a Google open source project which provides a set of Wear libraries that supplement the functionality provided by Compose for Wear OS and other Wear OS APIs.
Read about Horology
Horologist offers helpful Compose extensions:
Horologist will grow to provide developers with additional tools for building great Wear OS apps across different experiences. Check out the Horologist on Github to provide feedback and contribute general functionality that could be useful for Wear developers - and stay tuned for upcoming releases!
Many of the development principles for mobile Compose apply to Compose for Wear OS, so if you’re unfamiliar with the UI toolkit start with Jetpack Compose basics.
We’ve prepared a set of materials to help you get started with Compose for Wear OS:
Now that Compose for Wear OS has reached Beta it’s a great time to get started with Compose to quickly bring your app to life or refresh your existing UI. For more information about building apps for Wear OS, check out the developer site.
We’d love to hear from you about your experiences using Compose for Wear OS and what you are able to build! Join the discussion in the Kotlin Slack #compose-wear channel and please keep providing feedback on the issue tracker.
Happy Composing!
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