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.