Lightweight block ciphers are cryptographic primitives that are considered to be easy on the computer resources. The structure, block size and the number of rounds of the algorithms allow faster execution with little demand for the computing resources. On the hardware lightweightness is measured based on the execution latency, the bandwidth on communication channels and the amount of energy the computing device requires for execution of the algorithm.
Demand for lightweight algorithms in cryptography has been increased by the need to provide security for the upcoming pervasive information Technology Landscape which is highly dependent on small and cheap devices. Most of the devices in this category are extremely constrained in memory, computing power and in battery life.
It should be noted that the cryptographic algorithm though they are referred to as lightweight they are not weak algorithms. Their abilities however, might be challenged by very strong adversaries. A trade off however needs to be made based on the devices abilities and the security needs.
Several algorithms have been classified as lightweight, they include:
Keeloq
This is a 32bit block-cipher with a key space of 64 bits that was proposed by Gideon Kuhn in 1985 and later sold to microchip technology incorporation in 1995. The algorithm has been used to operate in constrained hardware environment. The algorithm uses nonlinear feedback shift registers to accept the 64 bits in order to encrypt 32 bits. The algorithm encoder encrypts the first 0 to 32 bits block in order to produce the 32 bit “hopping code” and hence the name Keeloq “code hopping”.
LED
This is a lightweight block Cipher that targets both hardware and software. The algorithm is based on the AES inner transformation. The algorithm is a 64 bit block cipher with 64 bit and 128 bits key spaces. The 64 bits makes 32 rounds and the 128 version has 48 rounds. Each block is represented by the 4by 4 nibble matrix. The nibble is optimized for hardware applications (KumarKushwaha, P. Singh and Kumar 1-7).
TWINE
This is a versatile block cipher that results from generalized Feistel Stricture. The algorithm provides balanced performance for both software and small hardware. It was proposed by Suzaki Minematsu and it is based on the implementation of Non-cyclic shift in order to improve diffusion and hence reduce the attackable rounds. The algorithm has a 64 bit block length with key space length of 80 bit or 128 bit hence giving the two types. The algorithm has 16- branches that improve the generalized Feistel structure with only S-boxes and XORs (Suzaki et al.).
L Block
This is a lightweight Block cipher that was proposed in the works by Wenling Wu and Lei Zhang. The algorithm targets both software and hardware platforms. The algorithm is modified by Festal network and has a cipher block of 64bits that are organized into two branches each with 32bits. In one branch Feistal function that contains the XOR output is rotated by 8bits. The algorithm has a key size of 80bits. The algorithm’s round function employs SP-networks with a confusion layer which has a small 4*4 S-boxes and the diffusion layer that is made up of 4 bit word permutation (Jeong and Lee 871-878).
References
KumarKushwaha, Prabhat, M. P. Singh, and Prabhat Kumar. "A Survey On Lightweight Block Ciphers". International Journal of Computer Applications 96.17 (2014): 1-7. Web.
Jeong, Ki-Tae, and Chang-Hoon Lee. "Differential Fault Analysis On Lightweight Block Cipher Lblock". The Journal of Korea Navigation Institute 16.5 (2012): 871-878. Web.
Suzaki, Tomoyasu et al. "TWINE: A Lightweight Block Cipher For Multiple Platform". SAC (2012): n. pag. Web. 20 Apr. 2016.
Zhang, Hai Feng and Chang Dong Xu. "Design of Remote Control Parking Lock Based On KEELOQ Encryption Technology". AMM 643 (2014): 21-24. Web.
