An arXiv preprint titled "Equivalent Non-linear Shift Register Transformations and Espresso" takes a closer look at the stream cipher Espresso, a hardware-efficient candidate for 5G security designed by E. Dubrova and M. Hell. According to the abstract, the cipher has two components, the first being a 256-bit binary non-linear feedback shift register (NFSR) with 14 feedback taps; the description of the second component is cut off in the source.
The paper's title suggests that it investigates equivalent non-linear shift register transformations. Such transformations can be used to rewrite an NFSR into a different form that preserves its output behavior, which may be relevant for security analysis or for optimising hardware implementation. However, the abstract provided does not include the paper's specific results or conclusions.
Because the source is a single truncated abstract, this digest can only report the announced scope and the design details visible in the text. No comparison with other work is possible from the available information.