Two architectures and VLSI implementations of the AES Proposal, Rijndael, are presented in this paper. These alternative architectures are operated both for encryption and decryption process. They reduce the required hardware resources and achieve high-speed performance. Their design philosophy is completely different. The first uses feedback logic and reaches a throughput value equal to 259 Mbit/sec. It performs efficiently in applications with low covered area resources. The second architecture is optimized for high-speed performance using pipelined technique. Its throughput can reach 3.65 Gbit/sec.