# Latency-Aware Accelerator of SIMECK Lightweight Block Cipher
## 1 Introduction  
Applications related to the internet-of-things (IoT) require secure communication with many (low-resource) embedded devices through the unsecured internet. The low-resource cryptographic applications or embedded devices determine the applications that demand low-area and power-efficient implementations of cryptographic algorithms/protocols for data security (in terms of encryption and decryption) [1]. In other words, such applications are also known as area/power-constrained applications. The low-resource embedded devices include radio-frequency-identification networks (RFID) [2, 3, 4], wireless sensor networks (WSNs) [5, 6, 7, 8, 9], smart cards [10], wireless body area networks (WBANs) [11], and the IoTs [12, 13]. These applications require secure communication through the unsecured internet [14, 1]. The challenge is to perform cryptographic computations in a reasonable time with limited implementation resources and power consumption. Consequently, efficient and dedicated implementation of cryptographic primitives are required to optimize performance (or latency), power, and area for low-resource embedded devices.  
To offer security services to RFID, WSNs, WBANs, and IoTs applications, symmetric and asymmetric cryptography algorithms are available in the literature [15, 16, 17, 18].  
The symmetric protocols/algorithms require a single key (namely, a private key) to execute the crypto operation while in asymmetric algorithms, two separate keys, i.e., public, and private, are required. In short, the comparison in the literature reveals that the symmetric algorithms are more beneficial for area and power-constrained cryptographic applications [1; 2; 7; 17].  
There are two categories, i.e., stream, and block, in the literature to classify the symmetric algorithms. A comprehensive comparison over various cryptographic algorithms is described in [1; 19]. The stream ciphers transform the plaintext into ciphertext by using a single byte of plaintext at a time. The block cipher transforms the complete block of plaintext with a fixed size into ciphertext at a time. Comparatively, the stream ciphers are more area- and power-efficient with performance overhead. With area and power parameters, the computation of cryptographic operations in a reasonable time is also essential [15; 17]. Then, in this case, block ciphers are more suitable. Any information that humans can comprehend without a decryption key or decryption device is called plaintext [1]. The term cipher is a form of algorithm which is used to convert plaintext into ciphertext. In another way, the unreadable output of encrypting algorithm is a cipher. Sometimes in the literature, a cipher is often used in place of ciphertext. In this work, a cipher determines the encryption algorithm. The ciphertext is a representation of original information into a format that humans cannot understand until the ciphertext is converted into plaintext using a secret key.  
There are two possible choices, i.e., software, and hardware, for the implementation of cryptographic algorithms. The software implementations are more flexible but with limited security and performance [1; 18; 15]. On the other hand, the hardware demonstrations of cryptographic protocols result in higher security and performance improvements with limited flexibility [1; 14; 16; 20; 21]. For an optimal solution, a host processor coupled with the crypto unit could be used as a co-design approach to perform the required cryptographic operations [1]. The host processor is responsible to pass crypto instructions to the associated crypto unit while a crypto unit is responsible to execute the required computations on hardware as used in [8] for securing the wireless sensor nodes. There is always a trade-off between security, flexibility, and performance. Consequently, we have preferred hardware demonstrations of a SIMECK [22] block cipher for data security by utilizing lower computational time, limited area, and low power.