A massively parallel implementation of an RC4 key search engine on an FPGA is described. The design employs parallelism at the logic level to perform many operations per cycle, uses on-chip memories to achieve very high memory bandwidth, floorplanning to reduce routing delays and multiple decryption units to achieve further parallelism. A total of 96 RC4 decryption engines were integrated on a single Xilinx Virtex XCV1000-E field programmable gate array (FPGA). The resulting design operates at a 50 MHz clock rate and achieves a search speed of 6.06 × 10⁶ keys/second, which is a speedup of 58 over a 1.5 GHz Pentium 4 PC.