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.
Passed all 7 tests
We answered the following questions in this order:
The answer is "yes".
If the answer were "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 were "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 were "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 were "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 were "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 were "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 were "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 were "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 were "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 were "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.
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 were "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 were "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.Distribution
Build Verifications
If you have a binary for a version that doesn't appear on the list, you can dropselect the file here to register it so somebody can verify its reproducibility:
Android
SPV using compact block filters
Compact block filters as in BIP158 are relatively tiny, probabilistic representation of the full blockchain which tell the client which block contains transactions relevant to specific addresses
Compared to SPV using bloom filters:
- Private: Avoid the leak of the client’s addresses to the full nodes it talks to. If the blocks are downloaded through TOR with new TOR identities for each request from different nodes, the privacy of this mode is almost as good as running a full node. An attacker would have to control a big part of the TOR network to still learn about which addresses are of interes.
- Fast: No re-scan of the full chain needed when importing a wallet. Compared to using an indexing server of the provider, it leaks no data to the provider
Compared to using an indexing server it is slower and more bandwidth is needed.
TOR - The Onion Router
TOR is a tool to shield the IP address of communicating parties. When communicating with a node on the TOR network, the communication is also necessarily end to end encrypted but not when communicating to a server on the internet that does neither use TOR nor ssl (https). Modern Androids allow to put apps behind a local TOR node independently of the provider offering TOR features. While this can be desirable to shield one’s IP address, it also might expose unencrypted data to different, probably more aware third parties. It also does not replace more advanced TOR features in which the wallet creates multiple TOR identities for different requests.
- Privacy: TOR shields the client’s IP address and thus his real world location or identity from servers it talks to.
- Speed: TOR means bouncing messages around a bit more with extra encryption. That makes it slower.
Buy with Credit Card
Buy coins with your credit card from within the product.
Ease of use.
Buying with Credit Card usually comes with huge fees and the same exchange provider often offers a better rate when not using via a wallet integration.
Fingerprint Authentication
Fingerprint authentication in Bitcoin wallets enhances security by adding a biometric layer to the access control mechanisms. This feature leverages the unique patterns of a user’s fingerprint to grant access to the wallet, making unauthorized access significantly more difficult. Biometric authentication is generally faster and more convenient than traditional methods like passwords or PINs, as it eliminates the need to remember complex combinations. This form of authentication is particularly useful in mobile wallet applications, where ease of access and security are paramount. Fingerprint authentication minimizes the risk of phishing or brute force attacks that typically target password-based systems. Furthermore, it can be combined with other forms of security measures, like PINs or passwords, to create a multi-factor authentication system for added security. The use of biometric data, however, raises concerns regarding privacy and data security. Users must be assured that their biometric data is stored securely and not vulnerable to unauthorized access or breaches.
- Enhanced security through a unique, non-replicable form of identification
- Convenience and speed of access compared to traditional methods
- Reduced risk of phishing and brute force attacks
Potential privacy concerns and dependency on device hardware capabilities.
NFC (Near Field Communication)
The wallet supports Near Field Communication (NFC) for wireless interaction with hardware wallets, payment terminals, or signing cards. NFC enables tap-to-sign or tap-to-pay functionality over a very short range (typically a few centimeters) without cables or QR codes.
- Convenience: Quick tap interaction — no cables to connect or QR codes to scan.
- Hardware wallet compatibility: Some hardware signing cards communicate exclusively via NFC.
- Requires NFC hardware on both devices.
- Very short range limits usability compared to QR-based air-gapped setups.
Update: 2024-07-24
Review: Breez Wallet Build
The build was successful with the command:
sudo docker build --no-cache -t breez_wallet -f com.breez.client.dockerfile .
Successfully built 8b7ab5a53f19
Successfully tagged breez_wallet:latest
We extracted the APK from the build and obtained the official APK from the Play Store. After unzipping both APKs using unzip --qqd, we compared them with:
diff --recursive from*
Significant differences were found between the generated APK and the Play Store version.
Binary files fromBuild/res/ZF.xml and fromOfficial/res/ZF.xml differ
Binary files fromBuild/res/zH.xml and fromOfficial/res/zH.xml differ
Only in fromOfficial/res: Zi.xml
Only in fromOfficial/res: zK.png
Only in fromBuild/res: Zk.png
Only in fromOfficial/res: zk.xml
Only in fromOfficial/res: zl.xml
Only in fromOfficial/res: Zl.xml
Only in fromOfficial/res: Zm.png
Only in fromOfficial/res: ZM.png
Only in fromOfficial/res: ZN.png
Only in fromBuild/res: zN.xml
Only in fromOfficial/res: zO1.png
Only in fromOfficial/res: zO.png
Only in fromOfficial/res: zp.json
Only in fromOfficial/res: z_.png
Only in fromBuild/res: -Z.png
Only in fromOfficial/res: Zp.png
Binary files fromBuild/res/zq.xml and fromOfficial/res/zq.xml differ
Only in fromOfficial/res: ZQ.xml
Only in fromOfficial/res: zR.png
Only in fromOfficial/res: Zs.png
Only in fromOfficial/res: zs.xml
Only in fromOfficial/res: zt.png
Only in fromOfficial/res: ZU.png
Only in fromOfficial/res: zv.png
Only in fromOfficial/res: ZW1.xml
Only in fromBuild/res: zw.png
Binary files fromBuild/res/ZW.xml and fromOfficial/res/ZW.xml differ
Binary files fromBuild/res/z_.xml and fromOfficial/res/z_.xml differ
Only in fromOfficial/res: -Z.xml
Only in fromOfficial/res: Z_.xml
Only in fromBuild/res: zy.png
Only in fromBuild/res: zZ.png
Binary files fromBuild/resources.arsc and fromOfficial/resources.arsc differ
Only in fromOfficial: storedclientpaymentchannel.proto
Only in fromOfficial: storedserverpaymentchannel.proto
Only in fromBuild: transport-backend-cct.properties
Only in fromBuild: transport-runtime.properties
Only in fromBuild: vision-common.properties
Only in fromBuild: vision-interfaces.properties
Only in fromOfficial: wallet.proto
With these many differences, the wallet is not verifiable.
Update: 2023-07-12: We tested the app another round with the apk provided in Play Store and the result was the same as previous test:
$ podman build --rm -t breez_build_apk --ulimit=nofile=8192 --cgroup-manager cgroupfs -f scripts/test/container/com.breez.client
$ podman run --rm --name breez_build_apk -it breez_build_apk
$ diff --recursive --brief ./FromPlay/ ./LocalBuild/
Files ./FromPlay/AndroidManifest.xml and ./LocalBuild/AndroidManifest.xml differ
Only in ./FromPlay/META-INF: GOOGPLAY.RSA
Only in ./FromPlay/META-INF: GOOGPLAY.SF
Only in ./FromPlay/META-INF: MANIFEST.MF
Files ./FromPlay/assets/dexopt/baseline.prof and ./LocalBuild/assets/dexopt/baseline.prof differ
Files ./FromPlay/classes.dex and ./LocalBuild/classes.dex differ
Files ./FromPlay/classes2.dex and ./LocalBuild/classes2.dex differ
Files ./FromPlay/lib/arm64-v8a/libapp.so and ./LocalBuild/lib/arm64-v8a/libapp.so differ
Files ./FromPlay/lib/arm64-v8a/libflutter.so and ./LocalBuild/lib/arm64-v8a/libflutter.so differ
Files ./FromPlay/lib/arm64-v8a/libgojni.so and ./LocalBuild/lib/arm64-v8a/libgojni.so differ
Only in ./LocalBuild/lib: armeabi-v7a
Only in ./LocalBuild/lib: x86
Only in ./LocalBuild/lib: x86_64
Only in ./FromPlay/: stamp-cert-sha256
Which is not verifiable.
Update: 2023-06-24: The provider released a new version but some of the building issues are not fixed yet. So building this project needs a lot of modifications that makes it hard to review. But finally we were able to build the project using this Dockerfile which is based on the Dockerfile provided by Emanuel.
Now it’s time to build the image and get a diff:
$ podman build --rm -t breez_build_apk --ulimit=nofile=8192 --cgroup-manager cgroupfs -f scripts/test/container/com.breez.client
$ podman run --rm --name breez_build_apk -it breez_build_apk
$ diff --recursive --brief ./FromGithub/ ./LocalBuild/
Files ./FromGithub/AndroidManifest.xml and ./LocalBuild/AndroidManifest.xml differ
Only in ./FromGithub/META-INF: GOOGPLAY.RSA
Only in ./FromGithub/META-INF: GOOGPLAY.SF
Only in ./FromGithub/META-INF: MANIFEST.MF
Files ./FromGithub/assets/dexopt/baseline.prof and ./LocalBuild/assets/dexopt/baseline.prof differ
Files ./FromGithub/classes.dex and ./LocalBuild/classes.dex differ
Files ./FromGithub/classes2.dex and ./LocalBuild/classes2.dex differ
Files ./FromGithub/lib/arm64-v8a/libapp.so and ./LocalBuild/lib/arm64-v8a/libapp.so differ
Files ./FromGithub/lib/arm64-v8a/libflutter.so and ./LocalBuild/lib/arm64-v8a/libflutter.so differ
Files ./FromGithub/lib/arm64-v8a/libgojni.so and ./LocalBuild/lib/arm64-v8a/libgojni.so differ
Only in ./LocalBuild/lib: armeabi-v7a
Only in ./LocalBuild/lib: x86
Only in ./LocalBuild/lib: x86_64
Only in ./FromGithub/: stamp-cert-sha256
With diffs in some binary files the wallet is not verifiable.
Original Analysis
A description to our liking. Here it is in full:
Breez is a Lightning Network client which makes paying in bitcoin a seamless experience. With Breez, anyone can send or receive small payments in bitcoin. It’s simple, fast and safe.
Ok, seamless, lightning, … nice.
Breez is a non-custodial service that uses lnd and Neutrino under the hood.
We want to hear that! Be your own bank!
For more technical information, please go to: https://github.com/breez/breezmobile.
So they are non-custodial and provide source code. More work for us :)
Warning: the app is still in beta and there is a chance your money will be lost. Use this app only if you are willing to take this risk.
That’s certainly inspiring more confidence than other apps with 2 months of track record claiming to be the best in the world. :)
Well, in terms of Build Instructions the app is lacking.
$ git clone git@github.com:breez/breezmobile.git
$ cd breezmobile/
$ git tag
0.5-openbeta
0.5.8-openbeta
0.5.9-openbeta
0.7-openbeta
0.8.improvements
As on the playstore it says “Current Version: Varies with device”, we go with what google gives us when we install it on a phone: 0.8-beta. The best match above would thus be the tag 0.8.improvements:
$ git checkout 0.8.improvements
$ cat android/app/build.gradle | grep version
versionCode 1
versionName "0.8-beta"
versionNameSuffix "-pos"
looks good so far. For now. We will not guess like this in the future.
Build breez.aar and bindings.framework as decribed in breez/breez
$ git submodule status
$
… so … the build instructions give no clue which version of breez/breez to build and there is no submodule?
$ git clone git@github.com:breez/breez.git
$ cd breez
$ git tag
0.5-openbeta
0.5.8-openbeta
Had there been a 0.8… in the breez project, we would have had a clue where to go next but absent that, there is no hope of reproducing the app. For now our verdict is: not verifiable.
An issue has been opened at https://github.com/breez/breezmobile/issues/247
iPhone
(Analysis from Android review)
Lightning Network support
The lightning Network (LN) is a layer two protocol that promises instant, low fee micro payments. Some wallets do not support receiving transactions which disqualifies them for this feature.
Transactions on LN are
- instant: It usually takes less than five seconds to finish a transaction.
- cheap: Transactions usually cost a tiny percentage (0.1%) of the transferred amount and might also be free.
- micro payments: The unit of account on the LN is micro Satoshis (mSat) or 0.00000000001 BTC.
LN is still in early development and several very feasible attacks are known that can cost users money or disrupt the network.
Why we list it for this wallet
Breez is a non-custodial Lightning Network client which makes paying in bitcoin a seamless experience. With Breez, anyone can send or receive small payments in bitcoin.
Source: Store
Buy with Credit Card
Buy coins with your credit card from within the product.
Ease of use.
Buying with Credit Card usually comes with huge fees and the same exchange provider often offers a better rate when not using via a wallet integration.
Why we list it for this wallet
Adding funds via credit card
Source: README
Fingerprint Authentication
Fingerprint authentication in Bitcoin wallets enhances security by adding a biometric layer to the access control mechanisms. This feature leverages the unique patterns of a user’s fingerprint to grant access to the wallet, making unauthorized access significantly more difficult. Biometric authentication is generally faster and more convenient than traditional methods like passwords or PINs, as it eliminates the need to remember complex combinations. This form of authentication is particularly useful in mobile wallet applications, where ease of access and security are paramount. Fingerprint authentication minimizes the risk of phishing or brute force attacks that typically target password-based systems. Furthermore, it can be combined with other forms of security measures, like PINs or passwords, to create a multi-factor authentication system for added security. The use of biometric data, however, raises concerns regarding privacy and data security. Users must be assured that their biometric data is stored securely and not vulnerable to unauthorized access or breaches.
- Enhanced security through a unique, non-replicable form of identification
- Convenience and speed of access compared to traditional methods
- Reduced risk of phishing and brute force attacks
Potential privacy concerns and dependency on device hardware capabilities.
Why we list it for this wallet
Biometric login
Source: README
SPV using compact block filters
Compact block filters as in BIP158 are relatively tiny, probabilistic representation of the full blockchain which tell the client which block contains transactions relevant to specific addresses
Compared to SPV using bloom filters:
- Private: Avoid the leak of the client’s addresses to the full nodes it talks to. If the blocks are downloaded through TOR with new TOR identities for each request from different nodes, the privacy of this mode is almost as good as running a full node. An attacker would have to control a big part of the TOR network to still learn about which addresses are of interes.
- Fast: No re-scan of the full chain needed when importing a wallet. Compared to using an indexing server of the provider, it leaks no data to the provider
Compared to using an indexing server it is slower and more bandwidth is needed.
Why we list it for this wallet
Expose Bitcoin Node (BIP157) configuration
Source: README
Free and Open Source (FOSS)
The wallet’s source code is published under a license approved by the Open Source Initiative (OSI) — such as MIT, GPL, Apache, or AGPL — allowing anyone to inspect, modify, and redistribute it. This is a prerequisite for independent security audits and reproducible builds. Licenses that are merely “source available” but not OSI-approved (e.g., those with Commons Clause restrictions, commercial use prohibitions, or other non-free terms) do NOT qualify. Reproducible builds are not sufficient alone.
-
Transparency: Anyone can verify what the code does — including whether it contains backdoors, bugs, or privacy-violating behavior.
-
Community auditing: More reviewers means vulnerabilities are more likely to be found and fixed.
-
Forkability: If the project is abandoned or goes rogue, the community can fork and continue it.
FOSS alone does not guarantee security. The released binary must also be reproducible from the public source to ensure users are actually running the code that was audited.
Why we list it for this wallet
https://github.com/breez/breezmobile
Source code is publicly available on GitHub. However, the License file returned 404: Not Found, so FOSS cannot be confirmed without a verified OSI-approved license file.
Source: README
NFC (Near Field Communication)
The wallet supports Near Field Communication (NFC) for wireless interaction with hardware wallets, payment terminals, or signing cards. NFC enables tap-to-sign or tap-to-pay functionality over a very short range (typically a few centimeters) without cables or QR codes.
- Convenience: Quick tap interaction — no cables to connect or QR codes to scan.
- Hardware wallet compatibility: Some hardware signing cards communicate exclusively via NFC.
- Requires NFC hardware on both devices.
- Very short range limits usability compared to QR-based air-gapped setups.
Why we list it for this wallet
NFC checkout
Source: README
Custom Node Connection
The wallet can be configured to connect to a user-specified, independently operated Bitcoin node — such as Bitcoin Core, Electrum Server, or other compatible full node software — instead of the wallet provider’s default servers. The key requirement is that the node is clearly independent from the wallet vendor: a third-party node the user controls or trusts.
-
Privacy: Transaction queries go to your own node rather than a third-party server, so no provider learns your wallet addresses or balances.
-
Security: No risk of a provider lying about your balance or the state of the network.
-
Sovereignty: Full independence from wallet provider infrastructure.
- Requires running and maintaining your own Bitcoin node.
- More complex initial setup compared to using the provider’s default servers.
Why we list it for this wallet
Support 3rd-party LSPs
Source: README
An issue has been opened at https://github.com/breez/breezmobile/issues/247
Product page updated by Leo Wandersleb, Emanuel, mohammad, keraliss, Daniel Andrei R. Garcia
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.