# Design of a Lightweight Cryptographic Scheme for Resource-Constrained Internet of Things Devices
## 2 Related Work  
A significant number of authors, in the current literature, have undertaken investigations into how to improve IoT security and privacy. This section derives input from current solutions for small cryptographic algorithms. They also discussed how to enhance the level of security for the IoT. In [6] a new variant lightweight cryptography algorithm for the Internet of Things is proposed, which is called New Variant Lightweight Cryptography (NVLC). The main idea of the design of NVLC is to use a 4-bit S-box with a lower signal delay in comparison to an 8-bit S-box. Additionally, it used the Whitening key idea at the beginning and end of encryption to raise the difficulty of key search and the difficulty of attacking the cipher. However, the encryption methods investigated the goal of a high level of security in the low-resource device for NVLC block cipher design. SFN [7], a new lightweight algorithm, employs a 96-bit key on a 64-bit block. The novel idea of the design is to use a different encryption method that takes both SP network structure and Feistel network structure to encrypt. Involution related properties of the nonlinear and linear components are employed into the design of SP network structure. The modified SP network structure enables the encryption and decryption program or circuit to work as the Feistel network structure. The encryption method satisfies the security requirements of different user levels. It gave a good performance in hardware at 1876 GEs. A study in [8] proposed a simplified new version of the round function of the original SIMON by reducing its impact by changing the shift numbers, so the first rotation is removed to enhance the speed of SIMON and execution time. The Feistel scheme is used to encrypt the lightweight block cipher LiCi [9]. LiCi has a 128-bit key, a 64-bit block, and 31 rounds. The LiCi design uses the substitution layer derived from the Karnaugh Map that applies 4 \(\times\) 4 S-boxes, which has been employed to reduce the logic gates of the S-box, and use circular shift by (3, 7). The encryption method offers good performance, both on hardware at 1153 GEs and on software platforms. BORON, a low-power cipher proposed in [10], boasts being ultra-weight and compact. It works with 128/80-bit keys and 64-bit plaintext over the SP network. Their methods used for encryption gave excellent performance of 1939 GEs in a small area. It performs efficiently on both hardware and software platforms. In [11], a family of low energy block ciphers called Midori is proposed, which is composed of two variants: Midori64 and Midori128. The design of Midori is to make use of cell-permutation layers 4 \(\times\) 4 involutory Binary MDS matrix to optimize diffusion speed, and two types bijective 4-bit S-boxes. The encryption methods satisfy the optimization goal of low energy for block cipher design. The study in [12] presented Simeck, a lightweight block cipher designed from components of other ciphers, SIMON and Speck. The study proved the ability to design ciphers that have less power consumption and are relatively smaller in area. The RECTANGLE algorithm [13] proposed new design criteria for the RECTANGLE S-box. The main idea of the design of RECTANGLE makes use of the bit-slice style in a lightweight manner, and was introduced for speeding up the software speed in the design of the DES and Serpent block cipher [14,15]. It offers a very low cost in hardware but also is very competitive in software speed. In [16], a lightweight, versatile block cipher called TWINE is proposed. The global structure of TWINE is a type-2 generalized Feistel structure (GFS). A round function of TWINE consists of a non-linear single 4-bit S-box rather than multiple ones, which can contribute to smaller (serialized) hardware and software implementations and different block shuffle from the original (cyclic shift), which can greatly improve the diffusion speed of type-2 GFS.