Mycelium Bitcoin Wallet

Published:

Wallet Logo

This Android app was first launched on 1st July 2013 and currently has more than 1000000 downloads, a 4.1 stars rating from 9013 users and the latest release is version 3.5.4.2.

Our last analysis was done on 13th July 2020 based on data found in their Google Play description and their website and their source repository. Our verdict was Reproducible when tested (details below).

We found these ways of contacting the developers:

Older reviews (show 12 of 14 reproducible)

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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 questionable coding practice. Nasa sends probes to space that crash due to software bugs despite a huge budget and stringent scrutiny.

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

Disclaimer: The authors of this project have contributed to Mycelium. Andreas Schildbach was so kind and independently tested and confirmed Mycelium’s verifiability here for a past version. Independent tests would be highly welcome!

Here we test if the latest version also can be verified, following the known procedure expressed in our test script:

As the reproducibility issue was not resolved yet, so the following results were obtained on a DigitalOcean server:

Results:
appId:          com.mycelium.wallet
signer:         b8e59d4a60b65290efb2716319e50b94e298d7a72c76c2119eb7d8d3afac302e
apkVersionName: 3.5.3.0
apkVersionCode: 3050300
apkHash:        847f61d6d6f24a459cba720adf0d9e1fd052431a2b49565ca424c13860a29f59

Diff:
Files /tmp/fromPlay_com.mycelium.wallet_3050300/apktool.yml and /tmp/fromBuild_com.mycelium.wallet_3050300/apktool.yml differ
Files /tmp/fromPlay_com.mycelium.wallet_3050300/original/META-INF/CERT.RSA and /tmp/fromBuild_com.mycelium.wallet_3050300/original/META-INF/CERT.RSA differ

This diff is what we want to see to call it reproducible.

Verdict Explained

Reproducible when tested At the time of this analysis, the app on Google Play was reproducible from the code provided by the developers!

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".