Help spread awareness for build reproducibility
Please help us spread the word, asking Coin Bitcoin Wallet to support reproducible builds via their Twitter!
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 ¶
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 source code.
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 reproducible which definitely includes not having to guess and so we remain until further notice with our prior verdict: not verifiable.
We could not verify that the provided code matches the binary!
As part of our Methodology, we ask:Is the published binary matching the published source code? If not, we tag it
Published code doesn’t help much if it is not what the published app was built from. That is why we try to reproduce the binary. We
- obtain the binary from the provider
- compile the published source code using the published build instructions into a binary
- compare the two binaries
- we might spend some time working around issues that are easy to work around
If this fails, we might search if other revisions match or if we can deduct the source of the mismatch but generally consider it on the provider to provide the correct source code and build instructions to reproduce the build, so we usually open a ticket in their code repository.
In any case, the result is a discrepancy between the app we can create and the app we can find on the app store 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.
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