This relatively new app currently has more than 1000 downloads and the latest APK (version Varies with device) was from 9th February 2020 and is newer than the below reviewed version of the app.
Our analysis was done on 30th December 2019 based on data found in their Playstore description and their website and their source repository. We discuss the issue with verification with the provider here. In our GitLab this app is discussed in Issue #83.
We found these ways of contacting the developers:
Help spread awareness for build verifiability
Please help us spread the word, asking Lightning: Fast Bitcoin Wallet to support verifiable builds via their Twitter!
The following Analysis is not a full code review! We plan to make code reviews available in the future but even then it will never be a stamp of approval but rather a list of incidents and bad coding practice. We cannot find and tell you all the dark secrets the wallet providers might have.
Do your own research!
Try out searching for "lost bitcoins", "stole my money" or "scammers" together with the wallet's name, even if you think the wallet is generally trustworthy. For all the bigger wallets you will find accusations. Make sure you understand why they were made and if you are comfortable with the provider's reaction.
From the description:
- Install the app and follow the setup instructions.
- Send a small amount of BTC to your wallet address (not more than you are willing to lose, it’s alpha)
- Wait a few minutes for the wallet to sync. Once completed, the app will open payment channels automatically. The funding transactions need to confirm just like regular on-chain transactions.
If it “sync”s and “open payment channels automatically”, it is probably a non-custodial app, although that is not said explicitly in the description.
But there is also a link to their GitHub.
There is no word on the Android build on the main Readme.md but under mobile we find something …
$ git clone https://github.com/lightninglabs/lightning-app $ cd lightning-app/ $ docker run --rm --volume=$PWD:/mnt --workdir=/mnt -it beevelop/cordova bash root@bf7373350a59:/mnt# npm install ... added 2140 packages from 1995 contributors and audited 943144 packages in 68.29s found 11 vulnerabilities (8 moderate, 3 high) run `npm audit fix` to fix them, or `npm audit` for details root@bf7373350a59:/mnt# cd mobile root@bf7373350a59:/mnt/mobile# npm install root@bf7373350a59:/mnt/mobile# cd android/ root@bf7373350a59:/mnt/mobile/android# yes | /opt/android/tools/bin/sdkmanager "build-tools;28.0.3" root@bf7373350a59:/mnt/mobile/android# ./gradlew bundleRelease > Task :app:bundleReleaseJsAndAssets warning: the transform cache was reset. Loading dependency graph, done. error Unable to resolve module `../../assets/rpc` from `/mnt/src/action/grpc-mobile.js`: The module `../../assets/rpc` could not be found from `/mnt/src/action/grpc-mobile.js`. Indeed, none of these files exist: * `/mnt/assets/rpc(.native||.android.js|.native.js|.js|.android.json|.native.json|.json|.android.ts|.native.ts|.ts|.android.tsx|.native.tsx|.tsx)` * `/mnt/assets/rpc/index(.native||.android.js|.native.js|.js|.android.json|.native.json|.json|.android.ts|.native.ts|.ts|.android.tsx|.native.tsx|.tsx)`. Run CLI with --verbose flag for more details. > Task :app:bundleReleaseJsAndAssets FAILED FAILURE: Build failed with an exception. * What went wrong: Execution failed for task ':app:bundleReleaseJsAndAssets'. > Process 'command 'node'' finished with non-zero exit value 1 * Try: Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights. * Get more help at https://help.gradle.org Deprecated Gradle features were used in this build, making it incompatible with Gradle 5.0. Use '--warning-mode all' to show the individual deprecation warnings. See https://docs.gradle.org/4.10.1/userguide/command_line_interface.html#sec:command_line_warnings BUILD FAILED in 30s 1 actionable task: 1 executed
So we threw what we know at it but failed there.
We did not take the route using Android Studio, as that should never be necessary as Android Studio itself uses gradle to build Android projects. For our purpose a tool with graphical interface, involving clicking buttons is not practical as build verification will be fully automated as it needs to be reevaluated after each release.
So for now we hope for better build instructions so we can soon give it another try and conclude this app is probably open source but not verifiable.
Not verifiable: The provided Open Source Code could not be verified to match the app released on Google Play
This verdict means that the provider did share some source code but that we could not verify that this source code matches the released app. This might be due to the source being released later than the app or due to the provided instructions on how to compile the app not being sufficient or due to the provider excluding parts from the public source code. In any case, the result is a discrepancy between the app we can create and the app we can find on GooglePlay and any discrepancy might leak your backup to the server on purpose or by accident.
As we cannot verify that the source provided is the source the app was compiled from, this category is only slightly better than closed source but for now we have hope projects come around and fix verifiability issues.
The app cannot be independently verified. If the provider puts your funds at risk on purpose or by accident, you will probably not know about the issue before people start losing money. If the provider is more criminally inclined he might have collected all the backups of all the wallets, ready to be emptied at the press of a button. The app might have a formidable track record but out of distress or change in management turns out to be evil from some point on, with nobody outside ever knowing before it is too late.