From the Expo build process's perspective, there is no difference whether an app is signed with an upload certificate or an app signing key. Either way, expo build:android will generate an APK signed with the keystore currently associated with your application. If you want to generate an upload keystore manually, you can do that the same way. Jun 04, 2019 This video is in Hindi Voice, How to Create Keystore file or JKS file and build/generate a signed APK. Subscribe this Channel, it's Free: https://www.
After the application has been built for release, the APK must be signed prior to distribution so that it can be run on an Android device. This process is typically handled with the IDE, however there are some situations where it is necessary to sign the APK manually, at the command line. The following steps are involved with signing an APK:
Create a Private Key – This step needs to be performedonly once. A private key is necessary to digitally sign the APK.After the private key has been prepared, this step can be skippedfor future release builds.
Zipalign the APK – Zipalign is an optimization processthat is performed on an application. It enables Android to interactmore efficiently with the APK at runtime. Xamarin.Android conductsa check at runtime, and will not allow the application to run ifthe APK has not been zipaligned.
Sign the APK – This step involves using the apksigner utility from the Android SDK and signing the APK with the private key that was created in the previous step. Applications that are developed with older versions of the Android SDK build tools prior to v24.0.3 will use the jarsigner app from the JDK. Both of these tools will be discussed in more detail below.
The order of the steps is important and is dependent on which tool used to sign the APK. When using apksigner, it is important to first zipalign the application, and then to sign it with apksigner. If it is necessary to use jarsigner to sign the APK, then it is important to first sign the APK and then run zipalign.
Prerequisites
This guide will focus on using apksigner from the Android SDK buildtools, v24.0.3 or higher. It assumes that an APK has already beenbuilt.
Applications that are built using an older version of the Android SDKBuild Tools must use jarsigner as described inSign the APK with jarsigner below.
Create a Private Keystore
A keystore is a database of security certificates that is createdby using the programkeytoolfrom the Java SDK. A keystore is critical to publishing aXamarin.Android application, as Android will not run applications thathave not been digitally signed.
During development, Xamarin.Android uses a debug keystore to sign theapplication, which allows the application to be deployed directly tothe emulator or to devices configured to use debuggable applications.However, this keystore is not recognized as a valid keystore for thepurposes of distributing applications.
For this reason, a private keystore must be created and used forsigning applications. This is a step that should only be performedonce, as the same key will be used for publishing updates and can thenbe used to sign other applications.
It is important to protect this keystore. If it is lost, then it willnot be possible to publish updates to the application with Google Play.The only solution to the problem caused by a lost keystore would be tocreate a new keystore, re-sign the APK with the new key, and thensubmit a new application. Then the old application would have to beremoved from Google Play. Likewise, if this new keystore is compromisedor publicly distributed, then it is possible for unofficial ormalicious versions of an application to be distributed.
Create a New Keystore
Creating a new keystore requires the command line toolkeytoolfrom the Java SDK. The following snippet is an example of how to usekeytool (replace <my-filename> with the file name for the keystoreand <key-name> with the name of the key within the keystore):
The first thing that keytool will ask for is the password for thekeystore. Then it will ask for some information to help with creatingthe key. The following snippet is an example of creating a new keycalled publishingdoc that will be stored in the filexample.keystore:
To list the keys that are stored in a keystore, use the keytool withthe – list option:
Zipalign the APK
Before signing an APK with apksigner, it is important to first optimize the file using the zipalign tool from the Android SDK. zipalign will restructure the resources in an APK along 4-byte boundaries. This alignment allows Android to quickly load the resources from the APK, increasing the performance of the application and potentially reducing memory use. Xamarin.Android will conduct a run-time check to determine if the APK has been zipaligned. If the APK is not zipaligned, then the application will not run.
The follow command will use the signed APK and produce a signed, zipaligned APK called helloworld.apk that is ready for distribution.
Sign the APK
After zipaligning the APK, it is necessary to sign it using a keystore. This is done with the apksigner tool, found in the build-tools directory of the version of the SDK build tools. For example, if the Android SDK build tools v25.0.3 is installed, then apksigner can be found in the directory:
The following snippet assumes that apksigner is accessible by thePATH environment variable. It will sign an APK using the key aliaspublishingdoc that is contained in the file xample.keystore:
When this command is run, apksigner will ask for the password to the keystore if necessary.
See Google's documentation for more details on the use of apksigner.
Note
According to Google issue 62696222, apksigner is 'missing' from the Android SDK. The workaround for this is to install the Android SDK build tools v25.0.3 and use that version of apksigner.
Sign the APK with jarsigner
Warning
This section only applies if it is nececssary to sign the APK with the jarsigner utility. Developers are encouraged to use apksigner to sign the APK.
This technique involves signing the APK file using the jarsigner command from the Java SDK. The jarsigner tool is provided by the Java SDK.
The following shows how to sign an APK by using jarsigner and the key publishingdoc that is contained in a keystore file named xample.keystore :
Note
When using jarsigner, it is important to sign the APK first, and then to use zipalign.
Related Links
-->Signing an app is a requirement to run an app on real devices during the development process or to distribute it via a beta program or in the Play Store. Without code signing, the app can only run on an emulator.
When App Center builds an Android application with a debug build type, a keystore associated with a developer isn't required but can be uploaded. These builds will be automatically code signed with a debug key. For a release build that will be deployed, you have to upload a keystore to App Center.
Upload Android App
Generating a keystore
If you don't currently have a keystore, you can generate one in Android Studio. You can find instructions on generating a keystore to sign APKs in Android Studio's official User Guide.
This is one of those golden nuggets in life where if you don’t grab it. Note: Yes, please run the xox.reg file for proper functionality! 
Setting up Code Signing
App Center supports three different ways of setting up code signing for Android apps. For all three methods, you first need to go to the build configuration and enable code signing:
Press generate and follow instructions to generate (public/private) key pair. Create a new 'authorizedkeys' file (with Notepad): Copy your public key data from the 'Public key for pasting into OpenSSH authorizedkeys file' section of the PuTTY Key Generator,. Dec 04, 2009 Peter Upfold walks you through the process of setting up a public/private key pair that you can use to log in to SSH servers from Terminal. To generate the missing public key again from the private key, the following command will generate the public key of the private key provided with the -f option. $ ssh-keygen -y -f /.ssh/idrsa /.ssh/idrsa.pub Enter passphrase: The -y option will read a private. Oct 06, 2018 Thats your SSH keys created, the private key is the idrsa and the public one is the idrsa.pub, don’t give out the private one always keep that one only on your local machine. Sharing the Public Key. Create an authorizedkeys in the.ssh directory. Generate private key from public key mac os. Jul 09, 2019 Public Key Infrastructure (PKI) security is about using two unique keys: the Public Key is encrypted within your SSL Certificate, while the Private Key is generated on your server and kept secret. All the information sent from a browser to a website server is encrypted with the Public Key, and gets decrypted on the server side with the Private Key.
- Go to your app in App Center.
- Go to Build.
- Go to the branch you want to configure by choosing it from the list.
- Either use the 'Settings' menu in the upper-right corner, or choose Configure if your branch is not configured for build yet.
- Enable Sign builds.
- Choose Save.
Then, depending on your scenario, use the most suitable of the three options in the sections below. The first option involves checking in credentials to your repository, while the other two use App Center to handle your credentials instead.
A. Storing everything in the Gradle configuration
You can specify the signing details in the build.gradle file. The signing details, along with all credentials and the keystore information, will be visible in the repository. First, add all the items you need to your code and check them in to your repository. Then in the build configuration in App Center, enable My Gradle settings are entirely set to handle signing automatically.
B. Uploading everything to App Center
You can upload the keystore and configure the signing credentials through App Center. In this case, App Center will first build your Android app and then run a signing step after the successful build.
Note
A build can only be signed once. Make sure you have no conflicts with signing configurations in your Gradle configuration for the chosen build variant. If there are signing settings both in App Center and in the Gradle file, the build may end up signed twice and this will lead to conflicts.
Set up your build configuration in App Center as follows:
- Disable My Gradle settings are entirely set to handle signing automatically.
- Upload your keystore file to the Keystore file upload file drop. You can drag the file onto the box or click it and browse for the file. Keystore files have the extension .keystore or .jks.
- Enter the keystore password, key alias, and key password in the corresponding fields. These values are the same ones you would otherwise enter in Android Studio when you sign a build.
C. Storing Signing Details in the Repository with Environment Variables
Use this method if your repository already contains the keystore, but you don't want to store the credentials there. At build time, the credentials will be provided as System properties to the Gradle build. See the following code sample on how to make use of them:
In the code above, securing values behind system properties injected into your build keeps your signing credentials safe – the values are encrypted and only available to the build agents at build time. You can provide the values through App Center. You can also hard code any of the values, and check them in to your repository. To use App Center to safeguard the values:
- Go to your build configuration.
- Make sure the checkbox called My Gradle settings are entirely set to handle signing automatically it not checked.
- Enter the keystore password, key alias, and key password in the corresponding fields. These values are the same ones you would otherwise enter in Android Studio when you sign a build.
If you use product flavors, you may need to adjust the code above so all your release configurations use the correct signing configuration.
Note
If you use the signingConfig option inside the buildTypes section in your build.gradle file, you may face code-signing errors during App Center build. This is especially relevant for apps that use React Native for Android version 0.60.x and higher:
To fix this issue you have to push a proper keystore used for signing to your repository and enable My Gradle settings are entirely set to handle signing automatically in your build configuration in the App Center portal.
Microsoft Upload App
In case you uploaded a keystore to the build configuration in the App Center portal, take into account that this approach will require to delete the signingConfig option from the buildTypes section of your build.gradle file if you didn't update it from the default state of the React Native project template.