This app was first launched on 1st May 2015 and currently has more than 50000 downloads, a 3.6 stars rating from 383 users and the latest APK (version 2.17.0) was from 12th February 2020 and is newer than the below reviewed version of the app.
Our analysis was done on 16th 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.
We found these ways of contacting the developers:
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.
Update: The provider closed the issue about reproducibility, so we do not assume this app to be reproducible any time soon.
Coin Bitcoin Wallet at least implies to be non-custodial with this feature:
Secure passphrase generation (your master private key), no one else can access your Coin.Space wallet.
but other features do not sound that promising:
Get started in seconds and access your wallet from any device: app or web.
They also claim
Over 20 million Wallets users.
and are around since early 2015, so we are hopeful to find more solid information on their website because in the Playstore description there is no word about open source.
There we again see strong claims about this wallet not being custodial:
Coin does not hold your keys for you. We cannot access accounts, recover keys, reset passphrase, nor reverse transactions. Protect your keys & always check that you are on correct URL. You are responsible for your security.
But nowhere on the website is a link to a source code repository.
Searching GitHub for their applicationId
com.coinspace.app we find two
repositories, with one looking
promising: One of the latest commits is tagged
v2.16.3 which is
exactly the version we see on Google Play.
Unfortunately there is nothing in terms of build instructions. Given there are two open issues, issue 14 and issue 17 asking about how to make this work, not specifically asking about Android but seeing these issues remaining unresolved in a year and almost two years I will postpone this analysis and conclude for now that this wallet is not verifiable.
Update: The developer replied to our request to resolve the issues we had but he closed the issue commenting:
Perhaps, it didn’t match because we don’t publish here our private parameters which we use for build. But you can be sure that our tags match App on Google Play store.
which was not our issue.
We are tempted to just try stuff with the Docker file there but our mission statement is that it should be easily verifiable which definitely includes not having to guess and so we remain until further notice with our prior verdict: 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.