Hi, From the signing documentation at http://developer.android.com/intl/zh-TW/guide/publishing/app-signing.html: When the system is installing an update to an application, if any of the certificates in the new version match any of the certificates in the old version, then the system allows the update. This indicates that an application can be signed with multiple certificates. This is an interesting option to allow multiple entities to sign an application. e.g: A system application which was initially signed by the device's manufacturer. Further updates could be signed by the developer. Am I misreading the documentation or is this really possible? If so, how? Is there any other way for an application to support different certificates and with that, having two or more entities sign it? Thanks, Rúben