# SC-SA: Byte-Oriented Lightweight Stream Ciphers Based on S-Box Substitution
### Current Research Status  
In the late 1980s and 1990s, to meet practical application needs, A5/1 was applied in the field of mobile communications and known as the GSM encryption algorithm. While the A5/1 algorithm was once considered secure, it has since been proven vulnerable to timing attacks. WG-7 [1] is a cipher designed by [PERSON] et al. in 2010. It is suitable for low-energy devices. It has an 80-bit key length and adopts a filter generator structure design. Its LFSR is defined in the finite field GF (\(2^{7}\)), and the nonlinear filter function uses the WG transformation. However, the filter generator structure is susceptible to fast correlation attacks and algebraic attacks, and WG-7 was quickly attacked after its publication. A2U2 is a lightweight stream cipher proposed by [PERSON] et al. in 2011 [2], specifically designed for encrypting RFID electronic tags. It has very low hardware implementation costs, requiring only 284 GE, making it one of the lightest stream cipher algorithms. [PERSON] et al. [3] significantly reduced the time complexity of real-time key recovery attacks on A2U2 under known plaintext attack patterns to 224. This means that attacks against this cipher can recover the entire key within seconds on a personal PC; the A2U2 algorithm has been completely broken. In 2004, the European Science Foundation initiated a cryptography project called the eSTREAM project, aiming to design and evaluate stream cipher algorithms to provide a series of efficient, secure, and reliable stream cipher algorithms to meet various application needs. After multiple rounds of competitions and evaluations, 20 excellent stream cipher algorithms were selected as the official recommended algorithms of the eSTREAM project. Grain-v1 [4] is one of the final seven selected algorithms in the eSTREAM project. It has high security characteristics. The initial version, Grain-v0, had vulnerabilities in the logical structure of its nonlinear feedback function g(\(\times\)) and nonlinear filter function h(\(\times\)), which made it susceptible to correlation attacks. However, the Grain structure has received widespread attention and has been proven to be relatively secure. Trivium algorithm, proposed by [PERSON] et al. [5], is another excellent candidate algorithm in the eSTREAM project. It combines shift registers and Boolean functions based on block ciphers, providing efficient hardware implementation and strong security. MICKEY 2.0 algorithm, introduced by [PERSON] et al. [6], supports configurations with different key lengths and initialization vector lengths, allowing for flexible adjustments according to specific application security requirements. Gimli algorithm, proposed by [PERSON] et al. [7], is a lightweight cipher based on permutations (such as bit-level, byte-level, and column-level permutations). It uses a triple iteration structure to enhance the security of the cipher structure. Salsa20 algorithm, introduced by [PERSON] et al. [8], is a high-speed and secure stream cipher widely used in communication and data protection fields. It has a simple structure, efficient hardware implementation, and provides strong security and resistance against attacks. ChaCha [9] is a variant of the Salsa20 stream cipher. It incorporates parallel and bitwise operations and consists of a matrix permutation operation and an iteration round function in its logical design. It demonstrates efficiency in both hardware and software implementations and offers improved security and resistance against attacks. Current research in non-lightweight cryptography spans various domains, including traditional stream ciphers, quantum cryptography, and image data encryption. In the realm of traditional stream ciphers, in 2019, [PERSON] and colleagues previously proposed \"ULTRA GRIDSEC\". This solution also secures data transfer within their newly developed peer-to-peer desktop grid framework \"HIMAN\".