Our wallet review process
We examine wallets starting at the code level and continue all the way up to the finished app that lives on your device. Provided below is an outline of each of these steps along with security tips for you and general test results.
Custody
Self-custodial: The user holds the keys
As part of our Methodology, we ask: Is the product self-custodial?
The answer is "yes". The user has control of their own keys.
Read more
Released
1st July 2013
Passed all 10 tests
We answered the following questions in this order:
The answer is "yes".
If the answer was "no", we would mark it as "Few users" and the following would apply:
The answer is "no". We marked it as "Few users".
We did not ask this question because we failed at a previous question.
If the answer was "no", we would mark it as "Few users" and the following would apply:
We focus on products that have the biggest impact if things go wrong and this one probably doesn’t have many users according to data publicly available.
The answer is "yes".
If the answer was "no", we would mark it as "Fake" and the following would apply:
The answer is "no". We marked it as "Fake".
We did not ask this question because we failed at a previous question.
If the answer was "no", we would mark it as "Fake" and the following would apply:
The bigger wallets often get imitated by scammers that abuse the reputation of the product by imitating its name, logo or both.
Imitating a competitor is a huge red flag and we urge you to not put any money into this product!
The answer is "yes".
If the answer was "no", we would mark it as "Not a wallet" and the following would apply:
The answer is "no". We marked it as "Not a wallet".
We did not ask this question because we failed at a previous question.
If the answer was "no", we would mark it as "Not a wallet" and the following would apply:
If it’s called “wallet” but is actually only a portfolio tracker, we don’t look any deeper, assuming it is not meant to control funds. What has no funds, can’t lose your coins. It might still leak your financial history!
If you can buy Bitcoins with this app but only into another wallet, it’s not a wallet itself.
The answer is "yes".
If the answer was "no", we would mark it as "A wallet but not for Bitcoin" and the following would apply:
The answer is "no". We marked it as "A wallet but not for Bitcoin".
We did not ask this question because we failed at a previous question.
If the answer was "no", we would mark it as "A wallet but not for Bitcoin" and the following would apply:
At this point we only look into wallets that at least also support BTC.
The answer is "yes".
If the answer was "no", we would mark it as "Can't send or receive bitcoins" and the following would apply:
The answer is "no". We marked it as "Can't send or receive bitcoins".
We did not ask this question because we failed at a previous question.
If the answer was "no", we would mark it as "Can't send or receive bitcoins" and the following would apply:
If it is for holding BTC but you can’t actually send or receive them with this product then it doesn’t function like a wallet for BTC but you might still be using it to hold your bitcoins with the intention to convert back to fiat when you “cash out”.
All products in this category are custodial and thus funds are at the mercy of the provider.
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.The answer is "yes".
If the answer was "no", we would mark it as "Custodial: The provider holds the keys" and the following would apply:
The answer is "no". We marked it as "Custodial: The provider holds the keys".
We did not ask this question because we failed at a previous question.
If the answer was "no", we would mark it as "Custodial: The provider holds the keys" and the following would apply:
A custodial service is a service where the funds are held by a third party like the provider. The custodial service can at any point steal all the funds of all the users at their discretion. Our investigations stop there.
Some services might claim their setup is super secure, that they don’t actually have access to the funds, or that the access is shared between multiple parties. For our evaluation of it being a wallet, these details are irrelevant. They might be a trustworthy Bitcoin bank and they might be a better fit for certain users than being your own bank but our investigation still stops there as we are only interested in wallets.
Products that claim to be non-custodial but feature custodial accounts without very clearly marking those as custodial are also considered “custodial” as a whole to avoid misguiding users that follow our assessment.
This verdict means that the provider might or might not publish source code and maybe it is even possible to reproduce the build from the source code but as it is custodial, the provider already has control over the funds, so it is not a wallet where you would be in exclusive control of your funds.
We have to acknowledge that a huge majority of Bitcoiners are currently using custodial Bitcoin banks. If you do, please:
- Do your own research if the provider is trust-worthy!
- Check if you know at least enough about them so you can sue them when you have to!
- Check if the provider is under a jurisdiction that will allow them to release your funds when you need them?
- Check if the provider is taking security measures proportional to the amount of funds secured? If they have a million users and don’t use cold storage, that hot wallet is a million times more valuable for hackers to attack. A million times more effort will be taken by hackers to infiltrate their security systems.
The answer is "yes".
If the answer was "no", we would mark it as "No source for current release found" and the following would apply:
The answer is "no". We marked it as "No source for current release found".
We did not ask this question because we failed at a previous question.
If the answer was "no", we would mark it as "No source for current release found" and the following would apply:
A wallet that claims to not give the provider the means to steal the users’ funds might actually be lying. In the spirit of “Don’t trust - verify!” you don’t want to take the provider at his word, but trust that people hunting for fame and bug bounties could actually find flaws and back-doors in the wallet so the provider doesn’t dare to put these in.
Back-doors and flaws are frequently found in closed source products but some remain hidden for years. And even in open source security software there might be catastrophic flaws undiscovered for years.
An evil wallet provider would certainly prefer not to publish the code, as hiding it makes audits orders of magnitude harder.
For your security, you thus want the code to be available for review.
If the wallet provider doesn’t share up to date code, our analysis stops there as the wallet could steal your funds at any time, and there is no protection except the provider’s word.
“Up to date” strictly means that any instance of the product being updated without the source code being updated counts as closed source. This puts the burden on the provider to always first release the source code before releasing the product’s update. This paragraph is a clarification to our rules following a little poll.
We are not concerned about the license as long as it allows us to perform our analysis. For a security audit, it is not necessary that the provider allows others to use their code for a competing wallet. You should still prefer actual open source licenses as a competing wallet won’t use the code without giving it careful scrutiny.
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.The answer is "yes".
If the answer was "no", we would mark it as "Failed to build from source provided!" and the following would apply:
The answer is "no". We marked it as "Failed to build from source provided!".
We did not ask this question because we failed at a previous question.
If the answer was "no", we would mark it as "Failed to build from source provided!" and the following would apply:
Published code doesn’t help much if the app fails to compile.
We try to compile the published source code using the published build instructions into a binary. If that fails, we might try to work around issues but if we consistently fail to build the app, we give it this verdict and open an issue in the issue tracker of the provider to hopefully verify their app later.
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.The answer is "yes".
If the answer was "no", we would mark it as "Not reproducible from source provided" and the following would apply:
The answer is "no". We marked it as "Not reproducible from source provided".
We did not ask this question because we failed at a previous question.
If the answer was "no", we would mark it as "Not reproducible from source provided" and the following would apply:
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
- 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 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.
Application build test result
Here we test if the latest version can be reproduced, following the known procedure expressed in our test script (?):
===== Begin Results =====
appId: com.mycelium.wallet
signer: b8e59d4a60b65290efb2716319e50b94e298d7a72c76c2119eb7d8d3afac302e
apkVersionName: 3.17.0
apkVersionCode: 3170000
verdict: reproducible
appHash: 2db36a0e65f2308646a50b3d13c6300096fd3a1d4b18d9bb3c633501e91ff8db
commit: e6c0398d90c3ad9d465c5ef2638ec98570709887
Diff:
Files /tmp/fromPlay_com.mycelium.wallet_3170000/META-INF/CERT.RSA and /tmp/fromBuild_com.mycelium.wallet_3170000/META-INF/CERT.RSA differ
Files /tmp/fromPlay_com.mycelium.wallet_3170000/META-INF/CERT.SF and /tmp/fromBuild_com.mycelium.wallet_3170000/META-INF/CERT.SF differ
Revision, tag (and its signature):
object e6c0398d90c3ad9d465c5ef2638ec98570709887
type commit
tag v3.17.0
tagger AlexanderPavlenko <AlexanderPavlenko@users.noreply.github.com> 1721053155 +0400
Mycelium Bitcoin Wallet v3.17.0
858054e52464f0b10a4769dd3843b054bf795feed5f311244d196194bf6926e4c7a8baac3deeddc8c604cd12929c1a81d10904c38bfe983943a316940b3a892b prodnet/release/mbw-prodnet-release.apk
deff0490602ef85d6da1f86047d9097eb64efe2a47583e413867a22f5626e8b8545271f2f027ed3cbe7a0df1477ccea70ed057b1d0eada25b43f0022efc1e7aa prodnet/release/mbw-prodnet-release.apk_unzip/META-INF/MANIFEST.MF
66a1e36a253cd4c4bda918c2a0c403fa0501dc9b0e1468b7ba3da6b89c09e102e83bf33fd76e986efff9bee4d8aea00aa75f94395644f662a7822bdd88538e9e btctestnet/release/mbw-btctestnet-release.apk
d49d4dc821bcf69f0f01a8f3546c4a3c736c97ea617d05c0d670998894cdc129ccff45daffb46ebe8859f693bec82b361078aa177c8839136f43d99056beae0e btctestnet/release/mbw-btctestnet-release.apk_unzip/META-INF/MANIFEST.MF
3865588e549527773f9cdd07edea001e1abf6d32ae6d5fbce0ec94d5bd094067bcefec18715b10ab9e90ba5b13236e918faf47bd3102059f063397444beb162e prodnet/debug/mbw-prodnet-debug.apk
ed07b1fa1a31b69f1f04aa1adb977e40e9e879c7c55186fd62739ea586d3177c7c2252606a23bf2d475d134724d20a76e17c7d1b2dbcf12750597388a693cd0c prodnet/debug/mbw-prodnet-debug.apk_unzip/META-INF/MANIFEST.MF
2ed330475a495474e7d3a1d0f3022752cd52955501669c5e0527a9f5f2e22752058cd2872b7c8bfe037495bfcc38aea6ffed0f6ed2690a64ba6232e9fea3ed5d btctestnet/debug/mbw-btctestnet-debug.apk
bbff0d892c2f33abcfdcbaf4f0af3c5dbaef360763e1481fac1dd958f231caabd8e02e42db608c9f4f7f8908917f69a64e146c7939b467806f56379a83d7baf3 btctestnet/debug/mbw-btctestnet-debug.apk_unzip/META-INF/MANIFEST.MF
===== End Results =====
This version is reproducible.
A recording of the test:
Disclaimer: Authors of this project have contributed to Mycelium.
Tests performed by Leo Wandersleb
Previous application build tests
Show moreDisclaimer
Our 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
In addition to reading our analysis, it is important to do your own checks. Before transferring any bitcoin to your wallet, look up reviews for the wallet you want to use. They should be easy to find. If they aren't, that itself is a reason to be extra careful.
<img src="https://walletscrutiny.com/images/social/android/com.mycelium.wallet.png">
