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Breez: Lightning Client & POS

Google Play
Latest Release: VARY 16th October 2024

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.

Developer

Breez Development LTD

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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

Source code

Public on github

Released

We could not determine when this product was originally released.

Application build

We could not verify that the provided code matches the binary!
See the last Issue we created.

See test result
Tested 24th July 2024

Distribution

Google Play

Platform notes

On the Google Play Store, there are many apps that have Bitcoin in their name or description but don’t allow the user to use Bitcoin or they don’t look like Bitcoin wallets but turn out to be. We run our tests and document our findings.

Passed 9 of 10 tests

We answered the following questions in this order:
We stopped asking questions after we encountered a failed answer.

Do many people use this product?

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.

Is this product the original?

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 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.
Is it a wallet?

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.

Is it for bitcoins?

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.

Can it send and receive bitcoins?

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.
Is the product self-custodial?

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 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.
Is the source code publicly available?

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.
Is the decompiled binary legible?

The answer is "yes".
If the answer was "no", we would mark it as "Obfuscated" and the following would apply:

The answer is "no". We marked it as "Obfuscated".

We did not ask this question because we failed at a previous question.
If the answer was "no", we would mark it as "Obfuscated" and the following would apply:

When compiling source code to binary, usually a lot of meta information is retained. A variable storing a masterseed would usually still be called masterseed, so an auditor could inspect what happens to the masterseed. Does it get sent to some server? But obfuscation would rename it for example to _t12, making it harder to find what the product is doing with the masterseed.

In benign cases, code symbols are replaced by short strings to make the binary smaller but for the sake of transparency this should not be done for non-reproducible Bitcoin wallets. (Reproducible wallets could obfuscate the binary for size improvements as the reproducibility would assure the link between code and binary.)

Especially in the public source cases, obfuscation is a red flag. If the code is public, why obfuscate it?

As obfuscation is such a red flag when looking for transparency, we do also sometimes inspect the binaries of closed source apps.

As looking for code obfuscation is a more involved task, we do not inspect many apps but if we see other red flags, we might test this to then put the product into this red-flag category.

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.
Can the product be built from the source provided?

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.
Does the published binary match the published source code?

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

  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.
Breez: Lightning Client & POS  App Store

Application build test result

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.

Tests performed by Leo Wandersleb, Emanuel, mohammad, keraliss

Previous application build tests

12th July 2023 0.15.refund_hotfix  
24th June 2023 0.15.refund_hotfix  

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.