1. A computer implemented method, comprising: receiving, by a device, a first code image from a host; in response to receiving the first code image, executing code stored in a read only memory (ROM) of the device to certify the first code image according to a chain of certificates and based upon a fingerprint of a root certificate stored in the ROM; deriving, by the device, a signature from the first code image using a key stored within the ROM when the first code image is certified; signing, by the device, the signature into a first header of the first code image; loading the first code image into a main memory of the device; verifying, at the device, the signature in the first header of the loaded first code image using the key stored within the ROM and without using the certificates; and in response to successfully verifying the signature of the loaded first code image, executing the verified first code image from the main memory of the device.