Abstract

The Advanced Encryption Standard (AES) is a symmetric key block cipher approved by the National Institute of Standards and Technology (NIST). AES replaced the Data Encryption Standard (DES) as a standard encryption algorithm within the United States government. It is widely used in both software and hardware applications and transactions. Different confidentiality modes of operation allow a symmetric key block cipher to provide additional data confidentiality by altering the output in respect to previously processed input data. These modes include Cipher Block Chaining, Cipher Feedback, Output Feedback and Counter modes. Electronic Codebook (ECB) mode does not enhance the confidentiality of the original cipher. This thesis presents an implementation of AES on a field-programmable gate array (FPGA). The design improves upon similar implementations that only employ ECB mode by supporting all five confidentiality modes of operation. The unified design supports all applicable key sizes and offers competitive throughput and resource utilization compared to designs lacking additional confidentiality modes. The design occupies 7452 slices of a Xilinx Virtex-II Pro XC2VP50 and features a maximum clock speed of 56.3 MHz. Throughputs up to 480.427 Mbps, 423.906 Mbps and 379.284 Mbps for 128-bit, 192-bit and 256-bit keys are produced for all five modes of operation. A straightforward level of key agility allows encryption and decryption operations to proceed uninterrupted at the expense of throughput. This feature is ideal when it is necessary to change the key for each block of data. A physical hardware prototype of the design is employed as further demonstration of the design's functional abilities.