WGU Introduction-to-Cryptography Practice Test Questions Answers

With IPsec ESP in transport mode, the payload of the original IP packet (typically the transport-layer segment and higher) is encrypted and integrity-protected between the two endpoints—here, the corporate server and the remote client. Because encryption is applied by the sending endpoint and removed only by the receiving endpoint, intermediate routers, switches, and monitoring devices in either network cannot view the protected payload while it is in transit. They may see outer IP headers and certain metadata needed for routing, but not the encrypted content protected by ESP. As a result, the packet’s contents are inspectable only at the endpoints: before encryption on the sender (plaintext exists in memory/stack before IPsec processing) and after decryption on the receiver (plaintext is restored for the application). This is true whether the traffic traverses internal networks or the Internet; the cryptographic boundary is between the endpoints participating in the IPsec SA. Therefore, inspection of the actual content is possible only on the devices at headquarters and offsite, before sending and after receiving, not by in-transit networks.

AES supports three standardized key sizes: 128, 192, and 256 bits, with a fixed block size of 128 bits. The maximum of these supported key sizes is 256 bits (AES-256). Key size affects resistance to brute-force key search: larger keys exponentially increase the search space. In practice, AES-128 is already considered strong against brute force with contemporary computing capabilities, while AES-256 is often chosen for compliance requirements, conservative security margins, or to hedge against future advances. AES-512 is not part of the AES standard; if 512-bit keys are desired, systems typically use different constructions (like using AES-256 in certain key-derivation or wrapping schemes) rather than changing AES itself. Therefore, the correct maximum supported AES key size is 256 bits.

Lightweight cryptography is designed for constrained environments—devices with limited CPU, memory, storage, bandwidth, and power (battery). Examples include IoT sensors, smart locks, RFID tags, embedded controllers, and industrial devices. Administrators choose lightweight algorithms and protocols to maintain reasonable security while fitting strict resource budgets and real-time constraints. The goal is not “weaker security because data is unimportant,” but rather efficient security that can still meet threat models under constraints. Option B captures this: embedded systems often cannot afford the computational cost of heavy cryptographic primitives (large key sizes, complex modes, frequent handshakes) or may struggle with latency and energy consumption. Option A is irrelevant because physical security of a desktop doesn’t remove the need for cryptography in communications or storage. Option C is the opposite of lightweight design. Option D is a poor justification; security design should be based on risk, and lightweight cryptography is not merely for “minimal protection,” but for practical deployability under constraints. Therefore, the correct reason is limited resources on embedded systems.

The expression 23 mod 6 asks for the remainder when 23 is divided by 6. Modular arithmetic is foundational in cryptography, especially in public-key systems (RSA, Diffie–Hellman, ECC) where operations occur in finite rings or fields. To compute 23 mod 6, identify the largest multiple of 6 that does not exceed 23. Multiples of 6 are 6, 12, 18, 24. Since 24 is greater than 23, the largest valid multiple is 18. Subtract: 23 − 18 = 5, so the remainder is 5. Therefore, 23 mod 6 = 5, which corresponds to option “05.” Modular reduction keeps numbers within a fixed range (0 to modulus−1), enabling stable arithmetic under wraparound behavior. In cryptographic protocols, this wraparound property is essential for defining groups and ensuring operations remain bounded and consistent.

The value 51 mod 11 is the remainder after dividing 51 by 11. Modular arithmetic is widely used in cryptography to keep computations within a finite set of residues, such as in RSA where values are taken modulo n, or in Diffie–Hellman where exponents and group elements are reduced modulo a prime. To compute 51 mod 11, find the largest multiple of 11 less than or equal to 51. Multiples of 11 are 11, 22, 33, 44, 55. The closest without exceeding 51 is 44. Subtracting gives 51 − 44 = 7, so the remainder is 7. Therefore, 51 mod 11 = 7, matching option “07.” This remainder is always in the range 0 through 10 because the modulus is 11. Such residue computations underpin the “wraparound” behavior that makes modular exponentiation and inverse computations well-defined in cryptographic groups.