A stored predefined unmodifiable bootable code set may be verified during code reprogramming of a device, and executed as a first stage of code reprogramming of the device. The predefined unmodifiable bootable code set may be stored in a locked memory such as a locked flash memory and may comprise code that enables minimal communication functionality of the device. The predefined unmodifiable bootable code set may be verified using a security algorithm, for example, a SHA-based algorithm. Information necessary for the security algorithm may be stored in a memory, for example, a one-time programmable read-only memory (OTP ROM). The stored information necessary for the security algorithm may comprise a SHA digest, a signature, and/or a key. A second stage code set may be verified and executed during the code reprogramming of the device subsequent to the verification of the stored predefined unmodifiable bootable code set.