Circuits, methods, and apparatus that prevent easy detection and erasure or modification of an encryption or encoding key. This key may be used to encode and decode a configuration bitstream for an FPGA or other programmable or configurable device. One embodiment of the present invention obfuscates a key then stores it in a memory array on an FPGA. This memory array may be a one-time programmable memory to prevent erasure or modification of the key. After retrieval from storage, a reverse or de-obfuscation is performed to recover the key. Further obfuscation may be achieved by proper layout of the relevant circuitry.