Blockchain Wallet. Bitcoin, Bitcoin Cash, Ethereum

4 minute read

Published:

Wallet Logo

This app was first launched on 1st February 2013 and currently has more than 5000000 downloads, a 4.1 stars rating from 84151 users and the latest APK is version Varies with device.

Our last analysis was done on 29th October 2019 based on data found in their Google Play description and their website and their source repository. We discuss verification with the provider in this issue.

We found these ways of contacting the developers:

Help spread awareness for build reproducibility

Please help us spread the word, asking Blockchain Wallet. Bitcoin, Bitcoin Cash, Ethereum to support reproducible builds via their Twitter!

Disclaimer

The following 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 bad coding practice. We cannot find and tell you all the dark secrets the wallet providers might have.

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

Update: In this comment to our now closed issue they claim to have addressed the issues we had earlier reported. Let’s see …

So they updated their README.md’s “quick start section”. This apparently refers to their quick_start.sh script:

We have version 6.34.7 installed.

$ git clone https://github.com/blockchain/My-Wallet-V3-Android.git
$ cd My-Wallet-V3-Android/
$ git tag | grep "6.34.7"
$ git show cfdb78c1d2f
commit cfdb78c1d2f9034cb2bd7193f9a46e1af5ad2095
Author: pauls <pstevens@blockchain.com>
Date:   Tue Jun 23 16:02:45 2020 +0100

    chore(release): AND-0000 Merge version update to develop

diff --git a/buildSrc/src/main/java/Dependencies.kt b/buildSrc/src/main/java/Dependencies.kt
index a24f63352..589ad8cba 100644
--- a/buildSrc/src/main/java/Dependencies.kt
+++ b/buildSrc/src/main/java/Dependencies.kt
@@ -7,8 +7,8 @@ object Versions {
     const val targetSdk = 28
     const val compileSdk = 28
 
-    const val versionCode = 549
-    const val versionName = "6.34.6"
+    const val versionCode = 550
+    const val versionName = "6.34.7"
 
     const val buildTools = "28.0.3"
 

so the 6.34.7 release was not tagged but we found a commit. The latest commit was tagged v6.35.0(551) and between those two commits, the issue was closed and there were actually many changes so as for build reproducibility we would require both the app from Google Play and our own build and we only have an old version from Google Play which we cannot build and we can only build a new version which is not available through Google Play yet, we can already call the release not verifiable but we can see if the build works at all:

$ git show master
commit 0ae8259f09cb0cf56594d596f9eda5cedc0afafb (HEAD -> master, tag: v6.35.0(551), origin/master, origin/HEAD)
Merge: 623245960 bb6c058f1
Author: dserrano <dserrano@blockchain.com>
Date:   Tue Jun 30 11:29:36 2020 +0100

    Merge branch 'master' of github.com:blockchain/My-Wallet-V3-Android

$ docker run --rm --volume $PWD:/mnt --workdir /mnt -it walletscrutiny/android:2
root@a464ee1156a5:/mnt# ./scripts/quick_start.sh
root@a464ee1156a5:/mnt# ./gradlew :app:assemble
...
FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':app:processEnvStagingDebugGoogleServices'.
> No matching client found for package name 'piuk.blockchain.android.staging'
...
BUILD FAILED in 8m 56s
211 actionable tasks: 150 executed, 61 from cache

piuk.blockchain.android.staging? That doesn’t look like what we want (piuk.blockchain.android). Let’s try again:

root@a464ee1156a5:/mnt# ./gradlew :app:assembleRelease
...
> Task :app:lintVitalEnvDevRelease
Calling mockable JAR artifact transform to create file: /root/.gradle/caches/transforms-2/files-2.1/f8d36826abe76fd5cf1d31ec8c8276c3/android.jar with input /opt/android-sdk/platforms/android-28/android.jar
/mnt/app/src/main/res/layout/activity_pit_verify_email_layout.xml:28: Error: @+id/toolbar_general is not a sibling in the same ConstraintLayout [NotSibling]
        app:layout_constraintTop_toBottomOf="@+id/toolbar_general" />
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

   Explanation for issues of type "NotSibling":
   Layout constraints in a given ConstraintLayout or RelativeLayout should
   reference other views within the same relative layout (but not itself!)

1 errors, 0 warnings

> Task :app:lintVitalEnvDevRelease FAILED

FAILURE: Build failed with an exception.

...

BUILD FAILED in 2m 55s
237 actionable tasks: 138 executed, 23 from cache, 76 up-to-date

… some try-and-error later …

root@a464ee1156a5:/mnt# ./gradlew :app:assembleEnvProdRelease -x :app:lintVitalEnvProdRelease
...
BUILD SUCCESSFUL in 45s
216 actionable tasks: 10 executed, 4 from cache, 202 up-to-date
root@a464ee1156a5:/mnt# ls app/build/outputs/apk/envProd/release/
blockchain-6.35.0-envProd-release-unsigned.apk  output.json

so now we can compile it. We assume the latest version from Google Play is in staged rollout and that we will get our hands on it shortly. In the meantime we remain with the verdict not verifiable.

Verdict Explained

Not verifiable: The provided Source Code could not be verified to match the app released on Google Play.

This verdict means that the provider did share some source code but that we could not verify that this source code matches the released app. This might be due to the source being released later than the app or due to the provided instructions on how to compile the app not being sufficient or due to the provider excluding parts from the public source code. In any case, the result is a discrepancy between the app we can create and the app we can find on GooglePlay 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 app 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 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.