A signing certificate is the cryptographic identity associated with an Android app. Developers use it to sign app packages, and Android checks the signature when an app is installed or updated. For a normal update, the new package must be signed with the same signing identity as the installed app, subject to Android’s signing rules.
This protects app continuity: a different publisher generally cannot replace an installed app through the ordinary update process. Attackers may instead use social engineering, such as persuading a user to uninstall a legitimate banking app before installing a trojanized lookalike. That is not a signing-certificate bypass; it exploits the user’s trust and installation choices. Users and defenders should treat unexpected uninstall-and-reinstall prompts or apps from unfamiliar sources as warning signs.