Method and apparatus for securing programming data of a programmable device

Configuration data for a programmable integrated circuit device is at least partially encrypted according to at least one encryption scheme. A plurality of key stores store a plurality of decryption keys for the at least one encryption scheme. Control circuitry identifies a required key from the at least partially encrypted configuration data and generates a key selection signal. Key selection circuitry responsive to the key selection signal reads the plurality of key stores and provides the required key to the control circuitry. The control circuitry may include decryption circuitry that decrypts the at least partially encrypted configuration data using the required key. In some embodiments, different portions of the configuration data, which may represent separate partial reconfigurations of the device, require different decryption keys. Keys may be generated from combinations of the contents of the key stores.