Patent ID: 8175276

Claim:
An encryption apparatus with diverse key retention schemes comprising: a first key register, configured as a non-volatile, read-only register, for storing a permanent cryptographic key; a second key register, configured as a read-write register, for storing one of a blank key and an erasable cryptographic key; a combining circuit coupled to said first and second key registers for generating an operating cryptographic key from said permanent cryptographic key and said one of said blank key and said erasable cryptographic key; an encryption engine coupled to said combining circuit and configured to encrypt plaintext data into ciphertext data using said operating cryptographic key and to decrypt said ciphertext data into said plaintext data using said operating cryptographic key; a read-write memory configured to store programming code; and a processor coupled to said encryption engine and to said read-write memory, said processor being configured to operate in accordance with said programming code to manage transference of said plaintext data and said ciphertext data into and out of said encryption engine; wherein said first key register, said combining circuit, and said encryption engine are collectively configured so that said permanent cryptographic key and said operating cryptographic key are inaccessible to said processor.