A secure register in a cable modem is accessed only if properly encrypted
data is received. The properly encrypted data is encrypted with a private
key known only to a cable modem termination station. The data is decrypted
with the public key stored in the cable modem. If the data and digital
signature match, then the result of a hash function verifies that the data
write is authorized. Configuration data, such as bandwidth data can be
written only to the protected register in the cable modem, only if the
data matches. Otherwise, the writing is prohibited. The method allows to
securely access registers in electronic device remotely, using insecure
communication media or channel. The method can be used to restrict access
to critical data in registers or memory elements of a device, including
ASICs, Flash and EEPROM memory components, to only positively
authenticated sources of data.