Cryptographic Techniques and Trends Questions

Broad knowledge of contemporary and emerging cryptographic primitives, protocols, and research directions. Includes understanding of authenticated encryption with associated data and why it is preferred over legacy constructions, password based key derivation functions such as PBKDF2, Argon2, and scrypt and the role of salting and key stretching, elliptic curve cryptography design and trade offs, and an awareness of post quantum cryptography candidates including lattice based, multivariate, and hash based approaches. Also encompasses familiarity with the modern threat landscape such as quantum computing risks, how cryptographic research progresses into standards and real world practice, how to follow relevant conferences and journals, and the ability to synthesize research findings into practical recommendations for design, migration, and policy decisions.

EasyTechnical

79 practiced

Describe the concrete risks of nonce (IV) reuse in AEAD schemes such as AES-GCM and ChaCha20-Poly1305. Explain what an attacker can learn or accomplish if nonces are reused under the same key, give specific attack consequences (e.g., keystream reuse, forgery), and note which AEAD designs are more or less tolerant of nonce mistakes.

MediumTechnical

80 practiced

Outline the core ideas behind lattice-based cryptography. Describe the Learning With Errors (LWE) and Short Integer Solution (SIS) problems at a conceptual level, explain the role of noise/error and how it is used to build primitives, and summarize how parameter choices (dimension, modulus, error distribution) influence both security and performance.

MediumTechnical

104 practiced

Explain the design differences between Argon2 variants (Argon2d, Argon2i, Argon2id) and scrypt. Discuss memory-hardness goals, data-dependent vs data-independent memory access patterns, resistance to GPU/ASIC acceleration, and side-channel trade-offs. State when Argon2id is the recommended default and why.

EasyTechnical

93 practiced

Explain what Authenticated Encryption with Associated Data (AEAD) is in practical terms. Describe a typical AEAD API (inputs: plaintext, associated-data, nonce; outputs: ciphertext, authentication tag), enumerate the security properties AEAD provides (confidentiality, integrity, authenticity, AAD protection), and explain why AEAD is preferred over ad-hoc combinations of encryption and MAC in modern protocols. Give two concrete AEAD examples and the threat scenarios AEAD directly defends against.

HardTechnical

74 practiced

You are the cryptography team lead and must recommend whether to adopt a new post-quantum KEM that is computationally fast but produces much larger ciphertexts and lacks complete formal proofs. Draft a concise recommendation memo that weighs security (proof maturity), operational impacts (latency, MTU, storage), interoperability, and standardization timelines, and propose a safe staged rollout and rollback plan if adoption is recommended.

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