FPGA Implementation(s) of a Scalable Encryption Algorithm

SEA is a scalable encryption algorithm targeted for small embedded applications. It was initially designed for software implementations in controllers, smart cards, or processors. In this letter, we investigate its performances in field-programmable gate array (FPGA) devices. For this purpose, a loop architecture of the block cipher is presented. Beyond its low cost performances, a significant advantage of the proposed architecture is its full flexibility for any parameter of the scalable encryption algorithm, taking advantage of generic VHDL coding. The letter also carefully describes the implementation details allowing us to keep small area requirements. Finally, a comparative performance discussion of SEA with the advanced encryption standard Rijndael and (a cipher purposed for efficient FPGA implementations) is proposed. It illustrates the interest of platform/context-oriented block cipher design and, as far as SEA is concerned, its low area requirements and reasonable efficiency.

I. Introduction

Scalable encryption algorithm (SEA) is a parametric block cipher for resource constrained systems (e.g., sensor networks, RFIDs) that has been introduced in [1]. It was initially designed as a low-cost encryption/authentication routine (i.e., with small code size and memory) targeted for processors with a limited instruction set (i.e., AND, OR, XOR gates, word rotation, and modular addition). Additionally and contrary to most recent block ciphers (e.g., the DES [2] and AES Rijndael [3], [4]), the algorithm takes the plaintext, key, and the bus sizes as parameters and, therefore, can be straightforwardly adapted to various implementation contexts and/or security requirements. Compared to older solutions for low-cost encryption like tiny encryption algorithm (TEA) [5] or Yuval's proposal [6], SEA also benefits from a stronger security analysis, derived from recent advances in block cipher design/cryptanalysis.