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AirGap Vault - Secure Secrets

Google Play
Latest Release: v 3.29.0 9th August 2023

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

Papers AG

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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

6th August 2018

Application build

The binary provided was reproducible from the code provided.
See the last Issue we created.

See test result
Tested 21st June 2023

Distribution

Google Play
4.3/5 stars via 110 ratings

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 all 10 tests

We answered the following questions in this order:

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.
AirGap Vault - Secure Secrets  App Store

Application build test result

We ran our test script (?) which delivered these results:

===== Begin Results =====
appId:          it.airgap.vault
signer:         486381324d8669c80ca9b8c79d383dc972ec284227d65ebfe9e31cad5fd3f342
apkVersionName: 3.26.0
apkVersionCode: 51797
verdict:        reproducible
appHash:        594a0c9fd380aeca626dd3c0b8e282589028404b6a1eee1e3b9f191ac0ace754
commit:         6730f178679329e72777e412156b22135ff81a1d

Diff:
Files /tmp/fromPlay_it.airgap.vault_51797/assets/public/index.html and /tmp/fromBuild_it.airgap.vault_51797/assets/public/index.html differ
Only in /tmp/fromBuild_it.airgap.vault_51797/assets/public: main.5184e2029b8e7e07.js
Only in /tmp/fromPlay_it.airgap.vault_51797/assets/public: main.bc1e4e3a4f2da280.js
Only in /tmp/fromPlay_it.airgap.vault_51797/META-INF: MANIFEST.MF
Only in /tmp/fromPlay_it.airgap.vault_51797/META-INF: PAPERS.RSA
Only in /tmp/fromPlay_it.airgap.vault_51797/META-INF: PAPERS.SF

Revision, tag (and its signature):
object 6730f178679329e72777e412156b22135ff81a1d
type commit
tag v3.26.0
tagger Mike Godenzi <m.godenzi@papers.ch> 1684820076 +0200

version 3.26.0
===== End Results =====

As mentioned in the test results there are a few minor changes. Let’s dig into it. We found that the diff in index.html is related to the file name change of main.*.js. main.bc1e4e3a4f2da280.js has been renamed to main.5184e2029b8e7e07.js, that’s a default behavior of Angular framework when building projects. Eventhough this behavior could be disabled to result the same bundle name with each build. So we openned an issue in the Airgap Vault repository. Also there is a minor diff in the js bundles:

diff <(fold -s -w 100 main.5184e2029b8e7e07.js) <(fold -s -w 100 main.bc1e4e3a4f2da280.js)
895c895
< Reflect.metadata(ie,UA)},"__metadata"),A(h,"tslib_awaiter"),A(function w(ie,UA){var 
---
> Reflect.metadata(ie,UA)},"__metadata"),A(h,"tslib_es6_awaiter"),A(function w(ie,UA){var

“tslib_awaiter” has been changed to “tslib_es6_awaiter” which also is a minor change and won’t affect the behavior of the wallet.

So we can still give it the verdict reproducible.

Tests performed by Leo Wandersleb

Previous application build tests

3.25.0  
3.18.0  
7th August 2022 3.17.2  
25th May 2022 3.17.0  
15th April 2022 3.16.0  
21st March 2022 3.15.1  
1st March 2022 3.15.0  
17th February 2022 3.14.0  
31st January 2022 3.13.1  
24th January 2022 3.13.0  
25th November 2021 3.12.0  
9th November 2021 3.11.2  
9th November 2021 3.11.1  
19th October 2021 3.11.0  
21st September 2021 3.10.0  
28th August 2021 3.9.0  
3rd August 2021 3.8.0  
24th April 2021 3.7.0  
3rd March 2021 3.6.2  
27th February 2021 3.6.2  
18th February 2021 3.6.1  
15th December 2020 3.5.1  
2nd September 2020 3.5.0  
21st August 2020 3.4.0  
22nd July 2020 3.3.0  
17th July 2020 3.3.0  
28th April 2020 3.2.0  
9th April 2020 3.1.0  
6th January 2020 3.0.0  
29th December 2019 3.0.0  
Show more

Disclaimer

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.