This app was first launched on 1st January 2015 and currently has more than 100000 downloads, a 4.1 stars rating from 565 users and the latest APK is version 3.3.7.
Our last analysis was done on 26th April 2020 based on data found in their Google Play description and their website and their source repository. We discuss verification with the provider in this issue.
We found these ways of contacting the developers:
- Website: blockstream.com/green
- Twitter: @Blockstream
- Facebook: Blockstream
- LinkedIn: company/blockstream
- Review of version 3.3.6 on 26th April 2020 (verdict: reproducible)
- Review of version 3.3.5 on 14th March 2020 (verdict: reproducible)
- Review of version 3.3.4 on 17th February 2020 (verdict: reproducible)
- Review of version 3.3.2 on 18th January 2020 (verdict: reproducible)
- Review of version 3.3.0 on 9th January 2020 (verdict: reproducible)
- Review of version 3.3.0 on 8th January 2020 (verdict: nonverifiable)
- Review of version 3.3.0 on 7th January 2020 (verdict: nonverifiable)
- Review of version 3.2.7 on 23rd November 2019 (verdict: reproducible)
Help spread awareness for build reproducibility
Please follow Green: Bitcoin Wallet and thank them for being reproducible 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.
With this script we get:
Results for appId: com.greenaddress.greenbits_android_wallet apkVersionName: 3.3.7 apkVersionCode: 22000337 apkHash: 847a67a5cfa498cf2e137b0a4306202322a35d4e3fba6bb90a269709e26e11ab Diff: Files /tmp/fromPlay_com.greenaddress.greenbits_android_wallet_22000337/apktool.yml and /tmp/fromBuild_com.greenaddress.greenbits_android_wallet_22000337/apktool.yml differ Only in /tmp/fromPlay_com.greenaddress.greenbits_android_wallet_22000337/original/META-INF: GREENADD.RSA Only in /tmp/fromPlay_com.greenaddress.greenbits_android_wallet_22000337/original/META-INF: GREENADD.SF Files /tmp/fromPlay_com.greenaddress.greenbits_android_wallet_22000337/original/META-INF/MANIFEST.MF and /tmp/fromBuild_com.greenaddress.greenbits_android_wallet_22000337/original/META-INF/MANIFEST.MF differ
And that diff looks exactly as it should look. Our verdict: This app is reproducible.
Reproducible: The provided Source Code matches the app released on Google Play
The app can be independently verified. If the provider puts your funds at risk on purpose or by accident, security researchers can see this if they care to look. It also means that inside the company engineers can verify that the release manager is releasing the app based on code known to all engineers on the team. A scammer would have to work under the potential eyes of security researchers. He would have to take more effort in hiding any exploit.
"Reproducible" does not mean "verified". There is good reason to believe that security researchers as of today would not detect very blatant backdoors in the public source code before it gets exploited, much less if the attacker takes moderate efforts to hide it.
To understand why some lines of difference are ok and others not one has to consider how app signing works. Android supports currently 3 signing schemes and in version 1 signing the signature is put inside the application file. As the tester must not have the release signing key, those files necessarily are missing or differ from the version on Google Play. The file "apktool.yml" was never part of the app and is generated by the analysis tool "apktool".