Zumo - Bitcoin Wallet App - Buy, Store, & Transfer

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This Android app currently has more than 1000 downloads, a 3.8 stars rating from 40 users and the latest release is version 2.10.1.

Our last analysis was done on 12th October 2020 based on data found in their Google Play description and their website. Our verdict was No source code found (details below).

We found these ways of contacting the developers:

Help spread awareness for build reproducibility

Please help us spread the word, asking Zumo - Bitcoin Wallet App - Buy, Store, & Transfer 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

💰 Provides full ownership of funds - your crypto is only owned by you!

sounds like non-custodial but

👮 Accounts are activated after an ID check!

doesn’t. Then again

📵 Lost your device? Reinstall, Login, & use your Backup Phrase to regain access

says something about “Backup Phrase” but if you have to “Login” first, we wonder if that backup phrase is shared with a server or if it is a BIP39 mnemonic at all.

Your Private Keys are managed on device, crypto currency is stored securely on the blockchain, and all of our codebase is developed in-house.

Again, this does not say anything about the keys being exclusively being on the device. Also what is that claim about the codebase? Well, let’s see …

As a non-custodial wallet, all your crypto is stored on the Blockchain.

Now that is explicit. Let’s see if there is public source code available …

… but we can’t find anything on Google Play or their website. The verdict is thus: not verifiable.

Verdict Explained

No source code found Without public source available, this app cannot be verified!

This verdict means that we could not find any source to compile the app from. Internally the company might do everything right but as we can't verify it, there is nothing protecting the user from an exit-scam where the provider releases an app that leaks the keys to the servers.

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.