A4: A Lightweight Stream Cipher

Lightweight ciphers are algorithms with low computational and spacial complexity. In the modern world of miniaturization, a lightweight cipher is used in constrained devices such as RFID tags, fire and security detectors, devices for wireless communications and other IoT devices. Stream ciphers are symmetric ciphers which encrypts the plain text bit stream with corresponding key stream to generate cipher text. Hence a stream cipher with low computational complexity and maximum security can be termed as a lightweight stream cipher. Many light weight stream ciphers are already existing. Each has its own vulnerabilities and spacial requirement. This paper has successfully developed, implemented, and analyzed a lightweight stream cipher - A4. Along with low computational cost, A4 also ensures paramount security and is less prone to the emerging cryptographic attacks.