Package signing is a cryptographic process that attaches a digital signature to software packages, such as mobile apps, updates, or installers. The signature lets a device or app store verify that the package came from the expected publisher and was not altered after it was signed. If the signature does not match, the package can be blocked or flagged as unsafe.
It matters because attackers often try to tamper with software in transit, swap in malicious updates, or repackage legitimate apps with hidden payloads. Strong signing helps defenders detect those changes and gives users and platforms a way to trust what they install. In layered distribution systems, such as one app store delivered through another, package signing helps separate publisher trust from marketplace trust: the storefront may curate the package, but the signature proves who built it and whether its contents stayed intact.