Abstract
This chapter presents an overview of the design approaches to stream ciphers. It defines the scope and presents generic constructions as well as attacks based on these constructions. The chapter also presents an overview of stream cipher competitions and standards. The largest class of stream ciphers is based on feedback shift registers (FSRs): this part distinguishes linear and nonlinear FSRs. The chapter discusses software‐oriented constructions based on large tables and then presents stream ciphers that are constructed based on block ciphers and large permutations. It also discusses authenticated encryption based on stream ciphers and with a treatment of low‐complexity stream ciphers that are optimized for use in advanced cryptographic protocols. Synchronous additive stream ciphers provide data confidentiality between two users who share a common secret key K. Symmetric cryptographic primitives have been mainly employed to provide confidentiality and authenticity for communicated and stored data.