US Patent 9911008 Microprocessor with on-the-fly switching of decryption keys

A microprocessor is provided in which an encrypted program can replace the decryption keys that are used to decrypt sections of the encrypted program. The microprocessor may be decrypting and executing a first section of the encrypted program when it encounters, decrypts, and executes an encrypted store-key instruction to store a new set of decryption keys. After executing the store-key instruction, the microprocessor decrypts and executes a subsequent section of the encrypted program using the new set of decryption keys. On-the-fly key switching may occur numerous times with successive encrypted store-key instructions and successive sets of encrypted instructions.