Final answer:
All Android apps must be digitally signed with a certificate for security. This signature confirms the app's integrity and authenticity.
Step-by-step explanation:
For security reasons, all Android apps must be digitally signed with a certificate. When an app developer has completed building an application, they must sign it with a private key using a certificate issued by a trusted certificate authority.
This signing process ensures that any subsequent updates to the app are from the legitimate developer and no one else. It verifies the integrity and authenticity of the app's code and data, making it difficult for malicious actors to tamper with the app without being detected.
Furthermore, this digital certificate contains the developer's public key which is used to verify the signature before an app is installed on an Android device. If the app's certificate does not match the signature, the Android system will not allow its installation, thereby protecting users from potential harm.