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Green: Bitcoin Wallet

latest release: 3.7.3 ( 30th September 2021 ) last analysed  19th December 2020 Not reproducible from source provided 
3.8 ★★★★★
106
22nd March 2019

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Help spread awareness for build reproducibility

Please help us spread the word, asking Green: 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.

If you find something we should include, you can create an issue or edit this analysis yourself and create a merge request for your changes.

The Analysis 

The description in the App Store is not explicit about the app being non-custodial and on their website we read:

Unmatched Security
Our innovative multisignature model uses dual private keys - one held by the user, and one by our servers. This allows us to enforce Two-Factor Authentication to protect your funds, while timelock smart contracts guarantee that users always retain full control of their coins.

This model never puts the provider in a position of being able to spend the user’s coins but the user cannot spend the coins neither until a predefined time elapsed, should their servers not cooperate.

While not uncontroversial, this is not custodial but so far nobody reproduced the build, so claims about security are not verifiable.

(lw)

Verdict Explained

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 Unreproducible! 

Published code doesn’t help much if it is not what the published binary was built from. That is why we try to reproduce the binary. We

  1. obtain the binary from the provider
  2. compile the published source code using the published build instructions into a binary
  3. compare the two binaries
  4. 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 binary we can create and the binary we can find for download 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 binary 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 product 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 product 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.