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Two lightweight block cipher families, Simon and Speck, have been proposed by researchers from the NSA recently. In this paper, we introduce Simeck, a new family of lightweight block ciphers that combines the good design components from both Simon and Speck, in order to devise even more compact and efficient block ciphers. For Simeck32/64, we can achieve 505 GEs (before the Place and Route phase) and 549 GEs (after the Place and Route phase), with the power consumption of 0.417 µW in CMOS 130nm ASIC, and 454 GEs (before the Place and Route phase) and 488 GEs (after the Place and Route phase), with the power consumption of 1.292 µW in CMOS 65nm ASIC. Furthermore, all of the instances of Simeck are smaller than the ones of hardware-optimized cipher Simon in terms of area and power consumption in both CMOS 130nm and CMOS 65nm techniques. In addition, we also give the security evaluation of Simeck with respect to many traditional cryptanalysis methods, including differential attacks, linear attacks, impossible differential attacks, meet-in-the-middle attacks, and slide attacks. Overall, all of the instances of Simeck can satisfy the area, power, and throughput requirements in passive RFID tags.

Outsourcing data to cloud servers, while increasing service availability and reducing users' burden of managing data, inevitably brings in new concerns such as data privacy, since the server may be honest-but-curious. To mediate the conflicts between data usability and data privacy in such a scenario, research of searchable encryption is of increasing interest.Motivated by the fact that a cloud server, besides its curiosity, may be selfish in order to save its computation and/or download bandwidth, in this paper, we investigate the searchable encryption problem in the presence of a semi-honest-but-curious server, which may execute only a fraction of search operations honestly and return a fraction of search outcome honestly. To fight against this strongest adversary ever, a verifiable SSE (VSSE) scheme is proposed to offer verifiable searchability in additional to the data privacy, both of which are further confirmed by our rigorous security analysis. Besides, we treat the practicality/efficiency as a central requirement of a searchable encryption scheme. To demonstrate the lightweightness of our scheme, we implemented and tested the proposed VSSE on a laptop (serving as the server) and a mobile phone running Android 2.3.4 (serving as the end user). The experimental results optimistically suggest that the proposed scheme satisfies all of our design goals.

Abstract. Due to the tight cost and constrained resources of highvolume consumer devices such as RFID tags, smart cards and wireless sensor nodes, it is desirable to employ lightweight and specialized cryptographic primitives for many security applications. Motivated by the design of the well-known Enigma machine, we present a novel ultralightweight cryptographic algorithm, referred to as Hummingbird, for resource-constrained devices in this paper. Hummingbird can provide the designed security with small block size and is resistant to the most common attacks such as linear and differential cryptanalysis. Furthermore, we also present efficient software implementation of Hummingbird on the 8-bit microcontroller ATmega128L from Atmel and the 16-bit microcontroller MSP430 from Texas Instruments, respectively. Our experimental results show that after a system initialization phase Hummingbird can achieve up to 147 and 4.7 times faster throughput for a size-optimized and a speed-optimized implementations, respectively, when compared to the state-of-the-art ultra-lightweight block cipher PRESENT [10] on the similar platforms.

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