NESTOR (encryption)

NESTOR is a symmetric-key block cipher submitted to the NIST Lightweight Cryptography Standardization Process. It's characterized by its design goals of achieving high performance in hardware and software implementations, particularly targeting resource-constrained environments. The cipher utilizes a substitution-permutation network (SPN) structure, incorporating operations such as S-boxes and linear diffusion layers to achieve confusion and diffusion, the two fundamental properties required for a secure cipher.

NESTOR's design features include variable key sizes and block sizes, providing flexibility for different security requirements and application contexts. The designers aimed to create a cipher resistant against common cryptanalytic attacks, such as linear and differential cryptanalysis, by carefully selecting the S-boxes and diffusion layers. The round function is typically iterated multiple times to ensure a high level of security. The specific details of the round function, including the S-box implementation, the structure of the linear diffusion layer, and the key schedule, define the unique characteristics of the NESTOR cipher.

As a candidate for standardization, NESTOR underwent extensive security analysis and performance evaluations by the cryptographic community. The results of these analyses informed the designers' decisions and potentially led to modifications to the cipher's structure and parameters. The overall aim was to balance security, performance, and implementation complexity, making NESTOR a viable option for lightweight cryptography applications. The success of NESTOR, like other submitted ciphers, depends on its demonstrated security, efficiency, and suitability for various use cases requiring lightweight cryptography.