A firmware or software update, patch, or upgrade image is authenticated by forcing its checksum to match a pre-determined value. The pre-determined value is known by a consumer electronic device in advance of propagating the image for installation. Upon propagation, the device determines a checksum value of the received imaged, and compares the checksum value to the pre-determined expected authenticity value. If they match, the image is installed. In an optional feature, the image is executed by the device and modifies the pre-determined checksum value to a next value, which is also shared or known by the image server. In this variation, no two images have the same expected value, and unauthorized images may be rejected for installation.