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Table of contents
1.
Introduction
2.
What is a Signed App?
3.
Signing Your App Using Debug Mode
4.
Signing Your App Using Release Mode
5.
Signing Your App Using Android Studio
6.
Signing Your App Automatically
6.1.
Manually Signing
7.
Considerations for Signing Your App
7.1.
App Modularity 
7.2.
App Update
7.3.
Code/data Sharing via Permissions 
8.
Keep Your Private Key Secure
9.
Expiration of Debug Certificate
10.
Frequently Asked Questions
10.1.
What do you mean by signing app?
10.2.
Is there a signature app for Android?
10.3.
Why is signing app necessary?
10.4.
What advantage does utilizing a signed APK provide?
10.5.
What does an Android Keystore do?
11.
Conclusion
Last Updated: Mar 27, 2024
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Signing App

Author Aditya kumar
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Introduction

You must have always heard about signing your app, but we do not know what it means. In this article, we will thoroughly discuss the signing app. We will discuss the steps required to sign an app and why it is important to sign an app.

signing app

When you are using an app, this is the first thing to check, is this app signed or not, if it is not, then it should be signed before using it on a device. Let’s discuss first what is a signed app.

What is a Signed App?

What is a Signed App?

With a private key, Android apps are signed. Every private key has a corresponding public certificate, which devices and services use to confirm that the app update is coming from the same source, ensuring that app updates are reliable. When an update's signature is identical to the signature of the loaded app, devices will only accept it.

Before an app can be installed on Android, it must be digitally signed with a certificate. Android does not require the certificate to be signed by a certificate authority to use it to identify the author of an app. Android apps commonly use self-signed certificates. The app developer keeps the private key for the certificate.

Apps can be signed in release or debug modes. When developing your app, you sign it in debug mode, and when you're ready to release it, you sign it in release mode. The Android SDK(Software Development Kit) generates a certificate to sign apps in debug mode. You must create your certificate to sign applications in release mode.

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Signing Your App Using Debug Mode

Signing Your App Using Debug Mode

You sign your app in debug mode using a debug certificate produced by the Android SDK tools. With this certificate, you can launch and debug your app without typing the password each time you modify the project because the private key has a known password.

Android Studio immediately signs your app in debug mode when you launch or debug your project from the IDE.

An app signed in debug mode can be used to run and debug on the emulator and on gadgets connected to your development machine via USB, but it cannot be shared with the public.

The debug setup utilises a default key with a known password and a debug Keystore by default. If absent, the debug Keystore is produced and stored in $HOME/.android/debug.keystore. The debug build type is configured to automatically utilize this debug SigningConfig.

Signing Your App Using Release Mode

Signing Your App Using Release Mode

You sign your app using your certificate in release mode:

1. Build a Keystore

A binary file called a Keystore house a collection of private keys. You need to keep your Keystore in a secure location.

2. Establish a private key

A private key represents the app-identifiable entity, such as a person or business.

3. Add the signing configuration to the app module's build file:

...
android {
    ...
    defaultConfig { ... }
    signingConfigs {
        release {
            storeFile file("yourreleasekey.keystore")
            storePassword "yourPassword"
            keyAlias "YourReleaseKey"
            keyPassword "YourPassword"
        }
    }
    buildTypes {
        release {
            ...
            signingConfig signingConfigs.release
        }
    }
}
...

4. With Android Studio, run the assembleRelease build process.

Your release key has been used to sign the app-release.apk package in app/build/apk.

Including your release key and Keystore passwords in the build, the file is not a good security practice. You can also set up the build file to ask you for these passwords during the build process or to get them from environment variables.

Using environment variables, you can get these passwords:

storePassword System.getenv("KEYSTOREPWD")
keyPassword System.getenv("KEYPWDHERE")

If you are starting the build from the command line, you should be prompted for these passwords by the build process:

storePassword System.console().readLine("\nKeystore password here: ")
keyPassword System.console().readLine("\nKey password here: ")

Once this process is complete, you can distribute your app and publish it on Google Play.

Make sure your Keystore and private key are both in a safe and secure area and that you have secure backups of both. If you publish an app to Play Store and then lose the key to sign it, you can not publish updates.

We will discuss thorough instructions on creating a private key and using Android Studio to sign your apps in release mode.

Signing Your App Using Android Studio

Signing Your App Using Android Studio

Follow these steps in Android Studio to sign your app in release mode:

  1. To create a signed APK, select Build from the menu bar.
Generate

2. Click Create new to start a new Keystore on the Generate Signed APK Wizard window.

new keystore
create new keystore

3. Step 4 should be taken if you already have a Keystore.

info

4. Fill out the necessary information on the New Key Store window.

new keystore window

5. To sign app upgrades with the same key throughout your app's life, your key's validity is at least 25 years.

release mode

Signing Your App Automatically

Signing Your App Automatically

You can set up your project in Android Studio so that it signs your release APK automatically. At the same time, it is being built:

  1. Right-click on your app in the project browser and choose Open Module Settings.
  2. Choose the module for your app from the list of modules on the Project Structure page.
  3. Select the "Signing" tab.
  4. Choose your Keystore file, give this signature configuration a name (you can create more than one), and fill out the necessary fields.
  5. Click “Build Types.”
  6. Select “Release Build.”
  7. Choose the signature configuration you just made from the list under Signing Config.
  8. Select “OK.”

Manually Signing

Manually Signing

Android Studio is not required to sign your app. Using common tools from the JDK and Android SDK, you may sign your app from the command line. Sign a app in release mode from the command line by typing:

1. Use keytool to create a private key. For example

$ keytool -genkey -v -keystore your-release-key.keystore
-alias name_of_alias -keyalg RSA -keysize 2048 -validity 20000

This example asks you to enter the Distinguished Name fields for your key and the passwords for the Keystore and key. The Keystore is then created as a file with the name "my-release-key.keystore." There is just one key in the Keystore, which is good for 20,000 days. The alias is a name you'll use to sign your app later.
 

2. If you want an unsigned APK, build your app in release mode.
 

3. Using jarsigner, sign your app with your private key:

$ jarsigner -verbose -sigalg SHA1withRSA -digestalg SHA1
-keystore my-release-key.keystore application.apk alias_name

You are prompted for the Keystore and key passwords in this case. To sign the APK, it is modified afterward. You should be aware that using various keys can sign an APK numerous times.
 

4. Check whether your APK is signed or not. For example

$ jarsigner -verify -verbose -certs new_application.apk

 

5. Using zipalign, align your final APK package.

$ zipalign -v 4 name_of_project-unaligned.apk name_of_project.apk

By ensuring that every uncompressed data begins with a specific byte alignment about the file's beginning, zipalign helps apps use less RAM.

Considerations for Signing Your App

Throughout your app's anticipated lifecycle, you should sign it with the same certificate. There are numerous justifications for doing so:

App Modularity 

If an app requests it, Android enables APKs signed by the same certificate to run in the same process, allowing the system to view them as a single app. Your app can be released in modules, and users can separately upgrade each module.

App Update

The system compares the certificate(s) in the new version with those in the older version when updating an app. If the certificates match, the system permits the change. The app must have a distinct package name if the new version is signed with a separate certificate; in this instance, the user installs the new version as a brand-new app.

Code/data Sharing via Permissions 

Android has signature-based permissions enforcement, enabling an app to make functionality available to other apps certified with a particular certificate. Your apps can securely exchange code and data by signing multiple APKs with the same certificate and using signature-based permissions checks.

Make sure your key has a validity term that surpasses the anticipated lifespan of that app if you intend to offer upgrades for it. A validity term of at least 25 years is advised. Users won't be able to smoothly upgrade to newer versions of your app when the validity time for their key ends.

Keep Your Private Key Secure

Both to you and the user, maintaining the security of your private key is crucial. Your writing identity and the user's trust are compromised if you give someone else access to your key or leave your Keystore and passwords in a public place where a stranger could access them.

If a third party were to obtain your key without your knowledge or consent, they may sign and distribute harmful apps that destroy or replace your legitimate apps. A person like this may also exploit your identity to sign and distribute malicious apps that destroy or steal user data or attack other apps or the operating system.

Here are some points for safeguarding your key:

  • Choose secure passwords for both the Keystore and the key.
  • Never share or lend your private key with anyone, and keep your Keystore and key passwords confidential.
  • Keep your private key's Keystore file in a safe, secure location.

Expiration of Debug Certificate

The self-signed certificate used to sign your application when it was in debug mode has a 365-day expiration date. You will get a build error when the certificate expires.

Simply deleting the debug.keystore file will solve the issue. 

The build tools will generate a fresh Keystore and debug key the following time you build.

Be aware that the build tools may mistakenly provide an expired debug certificate if your development system uses a non-Gregorian locale, preventing you from successfully compiling your app.

Frequently Asked Questions

What do you mean by signing app?

Developers can identify the application's author and update their software without having to create laborious interfaces and permissions by signing the application. The developer must sign each Android application before it may be used.

Is there a signature app for Android?

With the help of the Android app PDFelement, you may easily add your electronic signature to documents whenever and wherever.

Why is signing app necessary?

A private key is used to sign Android app signatures. Every private key has a corresponding public certificate that devices and services use to confirm that the app update is coming from the same source, ensuring that app updates are reliable.

What advantage does utilizing a signed APK provide?

Your apps can securely exchange code and data by signing multiple APKs with the same certificate and using signature-based permissions checks.

What does an Android Keystore do?

To make cryptographic keys more difficult to remove from the device, you can store them in a container using the Android Keystore system. Keys can be used for cryptographic operations once in the Keystore, but the key material cannot be exported.

Conclusion

In this article, we have discussed the signing app in android. We have discussed the signing app and how we can sign an app. We have discussed all the steps required for signing app. If you want to read more about android, you can check out our mentioned blogs.

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