Cryptographic Algorithm Design Principles Questions

Comprehensive understanding of the design and evaluation of cryptographic algorithms, covering both symmetric and asymmetric primitives and including block cipher and stream cipher constructions. Candidates should understand foundational principles such as confusion and diffusion, substitution box selection and properties, permutation networks and Feistel structures, round function design, key schedule construction, nonlinearity requirements, and the rationale for multiple rounds and security margins. For stream ciphers candidates should know keystream generator and internal state design including linear feedback shift register based constructions, filter and combiner functions, and the differences between synchronous and self synchronizing modes. For public key schemes candidates should understand underlying hardness assumptions, group and parameter selection, key generation and validation, padding and encoding considerations, and the distinct performance and security tradeoffs. Candidates should be able to analyze how design choices impact resistance to attacks including differential and linear cryptanalysis, algebraic and statistical attacks, timing and power side channel vulnerabilities, and chosen ciphertext and padding oracle attacks, and to articulate tradeoffs between security, implementation complexity, and performance. Candidates should also be able to evaluate and justify parameter choices, discuss how modes of operation and authenticated encryption affect real world use, and describe common validation and testing approaches such as cryptanalysis, test vectors, formal proofs, and implementation testing.