Blockchain Wallet. Bitcoin, Bitcoin Cash, Ethereum

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Wallet Logo

This app was first launched on 1st February 2013 and currently has more than 5000000 downloads, a 4.4 stars rating from 76234 users and the latest APK (version Varies with device) was from 21st March 2020.

Our analysis was done on 29th October 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 #2.

We found these ways of contacting the developers:

Help spread awareness for build verifiability

Please help us spread the word, asking Blockchain Wallet. Bitcoin, Bitcoin Cash, Ethereum to support verifiable builds via their Twitter!

Disclaimer

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.

The Analysis

Blockchain Wallet is not custodial.

It doesn’t claim to be verifiable.

The build verification turned out to not be possible as the wallet does not build with the files provided.

The provider should make the repository compilable as is. With a way to compile the app, verification might then be possible for all but this file. The security implications of a modified google-services.json are minor compared to not being able to compile the project at all.

Other observations

Blockchain Wallet does have a bug bounty program.

Libraries are version pinned.

Libraries get pulled from nine repositories which might have some security implications, given it is not straight forward to see which repository gets to provide which library. jcenter() being the last in the list is remarkable in so far as it’s one of the more popular and trusted repositories, which we would not say about some of the others. Any package expected to be loaded from jcenter() thus could trivially get provided by said others. But trustworthiness of repositories and dependencies is a whole different topic anyway …

Interpretation

Blockchain Wallet cannot be verified to match its available public code.

Verdict Explained

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.