Cryptographic Algorithm Implementation Questions

Skills and knowledge for correctly implementing cryptographic algorithms and primitives in code. Candidates should be able to translate algorithm specifications and mathematical definitions into correct implementations, handling binary data layouts, bit operations such as shifts and exclusive or, and large integer arithmetic required for modular operations. Expect to implement core operations and components including Advanced Encryption Standard encryption rounds, Rivest Shamir Adleman modular exponentiation, Secure Hash Algorithm 256 message scheduling, substitution boxes in block ciphers, mixing functions, substitution and permutation operations, and simplified cipher operations for demonstration. Understand appropriate data structure choices and their performance and security implications, including constant time considerations, endianness, padding rules, and proper randomness. Implement and verify against official test vectors and build verification procedures and test harnesses. Emphasize correctness and clear explanation over premature optimization and recognize when to prefer well vetted cryptographic libraries to custom implementations.