Abstract. With the establishment of the AES the need for new block ciphers has been greatly diminished; for almost all block cipher applications the AES is an excellent and preferred choice. However, despite recent implementation advances, the AES is not suitable for extremely constrained environments such as RFID tags and sensor networks. In this paper we describe an ultra-lightweight block cipher, present. Both security and hardware efficiency have been equally important during the design of the cipher and at 1570 GE, the hardware requirements for present are competitive with today's leading compact stream ciphers.

Abstract. We present a new block cipher LED. While dedicated to compact hardware implementation, and offering the smallest silicon footprint among comparable block ciphers, the cipher has been designed to simultaneously tackle three additional goals. First, we explore the role of an ultra-light (in fact non-existent) key schedule. Second, we consider the resistance of ciphers, and LED in particular, to related-key attacks: we are able to derive simple yet interesting AES-like security proofs for LED regarding related-or single-key attacks. And third, while we provide a block cipher that is very compact in hardware, we aim to maintain a reasonable performance profile for software implementation.

Much research has focused on providing RFID tags with lightweight cryptographic functionality. The HB + authentication protocol was recently proposed [1] and claimed to be secure against both passive and active attacks. In this note we propose a linear-time active attack against HB + .

The innovative HB + protocol of Juels and Weis [10] extends device authentication to low-cost RFID tags. However, despite the very simple on-tag computation there remain some practical problems with HB + and despite an elegant proof of security against some limited active attacks, there is a simple man-in-the-middle attack due to Gilbert et al. [8]. In this paper we consider improvements to HB + in terms of both security and practicality. We introduce a new protocol that we denote random-HB #. This proposal avoids many practical drawbacks of HB + , remains provably resistant to attacks in the model of Juels and Weis, and at the same time is provably resistant to a broader class of active attacks that includes the attack of [8]. We then describe an enhanced variant called HB # which offers practical advantages over HB + .

In this paper we consider some cryptographic implications of integrated circuit (IC) printing. While still in its infancy, IC-printing allows the production and personalisation of circuits at very low cost. In this paper we present two block ciphers PRINTcipher-48 and PRINTcipher-96 that are designed to exploit the properties of IC-printing technology and we further extend recent advances in lightweight block cipher design.