Graduation Year

2003

Document Type

Thesis

Degree

M.S.Cp.E.

Degree Granting Department

Computer Engineering

Major Professor

Dr. Murali R. Varanasi, Ph.D.

Committee Member

Dr. N. Ranganathan, Ph.D.

Committee Member

Dr. Sanjukta Bhanja, Ph.D.

Keywords

Hardware architecture, AES, cryptography, real time key scheduling

Abstract

The increasing application of cryptographic algorithms to ensure secure communications across virtual networks has led to an ever-growing demand for high performance hardware implementations of the encryption/decryption methods. The inevitable inclusion of the cryptographic algorithms in network communications has led to the development of several encryption standards, one of the prominent ones among which, is the Rijndael, the Advanced Encryption Standard. Rijndael was chosen as the Advanced Encryption Standard (AES) by the National Institute of Standard and Technology (NIST), in October 2000, as a replacement for the Data Encryption Standard (DES). This thesis presents the architecture for the VLSI implementation of the Rijndael, the Advanced Encryption Standard algorithm.

Rijndael is an iterated, symmetric block cipher with a variable key length and block length. The block length is fixed at 128 bits by the AES standard [4]. The key length can be designed for 128,192 or 256 bits. The VLSI implementation, presented in this thesis, is based on a feed-back logic and allows a key length specification of 128-bits. The present architecture is implemented in the Electronic Code Book(ECB) mode of operation. The proposed architecture is further optimized for area through resource-sharing between the encryption and decryption modules. The architecture includes a Key-Scheduler module for the forward-key and reverse-key scheduling during encryption and decryption respectively. The subkeys, required for each round of the Rijndael algorithm, are generated in real-time by the Key-Scheduler module by expanding the initial secret key.

The proposed architecture is designed using the Custom-Design Layout methodology with the Cadence Virtuoso tools and tested using the Avanti Hspice and the Nanosim CAD tools. Successful implementation of the algorithm using iterativearchitecture resulted in a throughput of 232 Mbits/sec on a 0.35[mu] CMOS technology. Using 0.35[mu] CMOS technology, implementation of the algorithm using pipelining architecture resulted in a throughput of 1.83 Gbits/sec. The performance of this implementation is compared with similar architectures reported in the literature.

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