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NEW QUESTION # 18
(Which cipher uses shifting letters of the alphabet for encryption?)
- A. Bifid
- B. SHA-1
- C. Vigenere
- D. Caesar
Answer: D
Explanation:
The Caesar cipher is the classic substitution cipher that encrypts by shifting letters of the alphabet by a fixed number of positions (e.g., shift by 3: A#D, B#E, etc.). It is a monoalphabetic cipher because a single shift value is applied uniformly across the entire message, making it simple and vulnerable to frequency analysis and brute force (only 25 meaningful shifts in the Latin alphabet). Vigenere also involves shifting, but it uses a repeating keyword to vary the shift per character (polyalphabetic), whereas the question's phrasing typically points to the fundamental "shift cipher," which is Caesar.
SHA-1 is a cryptographic hash function, not a cipher. Bifid is a fractionation cipher combining Polybius square coordinates and transposition, not a direct shifting method. Therefore, the cipher that uses shifting letters of the alphabet for encryption is the Caesar cipher.
NEW QUESTION # 19
(How does adding salt to a password improve security?)
- A. Salt ensures two people do not have the same password.
- B. Salt prevents users from reusing the same password.
- C. Salt enforces the complexity rules for passwords.
- D. Salt creates a different hash if two people use the same password.
Answer: D
Explanation:
A salt is a unique, random value stored alongside a password hash and combined with the password during hashing. Its main security benefit is that it ensures identical passwords do not produce identical hashes across different accounts or systems. If two users choose the same password, their stored hashes will differ because their salts differ, which directly prevents attackers from spotting shared passwords by comparing hashes. Salts also defeat precomputation attacks such as rainbow tables, because an attacker would need to regenerate tables for each possible salt value-a task that becomes infeasible when salts are large and unique per password. Salt does not enforce password complexity rules (that's a policy/validation function), does not guarantee users choose different passwords, and does not prevent password reuse across sites. The correct statement is that salt makes the resulting hash different even for the same password, improving resistance to offline cracking at scale and eliminating the "same hash
= same password" shortcut attackers rely on.
NEW QUESTION # 20
(Which mechanism can be applied to protect the integrity of plaintext when using AES?)
- A. RC4
- B. Kerberos key sharing
- C. Message Authentication Code (MAC)
- D. RSA
Answer: C
Explanation:
AES by itself is a symmetric block cipher that provides confidentiality, but not guaranteed integrity unless used in an authenticated mode. To protect integrity of the plaintext (ensuring it has not been altered), a Message Authentication Code (MAC) can be applied. In the classic Encrypt-then-MAC pattern, the sender encrypts the plaintext with AES and then computes a MAC (often HMAC-SHA-256 or CMAC-AES) over the ciphertext (and relevant headers). The receiver verifies the MAC before attempting decryption, preventing tampering and many padding-oracle style vulnerabilities.
Alternatively, AES can be used in an AEAD mode like AES-GCM, which produces an authentication tag serving a similar purpose, but among the listed options the general integrity mechanism is "MAC." RC4 is an unrelated stream cipher and does not provide integrity. RSA is asymmetric and not the standard integrity add-on for AES-encrypted bulk data. Kerberos is an authentication protocol and key distribution system, not a message integrity primitive. Therefore, to protect plaintext integrity when using AES, the correct mechanism is a Message Authentication Code.
NEW QUESTION # 21
(Why should an administrator choose lightweight cryptography?)
- A. The payload requires complex rounds of encryption.
- B. The data requires minimal protection due to the sensitivity level.
- C. The desktop is in a secure area of the building.
- D. The embedded system has limited resources.
Answer: D
Explanation:
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.
NEW QUESTION # 22
(What is the value of 23 mod 6?)
- A. 04
- B. 03
- C. 06
- D. 05
Answer: D
Explanation:
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.
NEW QUESTION # 23
(A company wants to use certificates issued by a root CA to demonstrate to customers that it is a legitimate company being hosted by a cloud provider. Who needs to trust the root CA public key?)
- A. The buyer and the Federal Trade Commission
- B. The cloud provider and the seller
- C. The Federal Trade Commission and the cloud provider
- D. The seller and the buyer
Answer: D
Explanation:
In a public key infrastructure, trust in a certificate ultimately depends on the relying party's trust anchor set-typically the root CA certificates preinstalled in a customer's browser/OS trust store. For customers to accept the company's certificate as legitimate, the buyer (customer) must trust the root CA public key (or an intermediate chained to it) so they can validate the certificate chain and signatures. The seller (the company) also must trust and rely on the root CA public key to build and present a valid chain and to make operational decisions based on that CA's issuance and revocation mechanisms; practically, the seller selects a CA whose root is widely trusted by customers. The cloud provider's trust is not what makes the certificate valid to customers; the provider may terminate TLS or pass traffic through, but customer validation is based on the chain to a trusted root. Government agencies like the FTC are not part of the cryptographic trust path for TLS certificate validation.
Therefore, among the given options, the correct pairing is the seller and the buyer, reflecting both the issuer selection/usage by the company and the relying-party validation by customers.
NEW QUESTION # 24
(Which type of exploit involves looking for different inputs that generate the same hash?)
- A. Algebraic attack
- B. Linear cryptanalysis
- C. Birthday attack
- D. Differential cryptanalysis
Answer: C
Explanation:
A birthday attack targets hash functions by exploiting the birthday paradox: collisions (two different inputs producing the same hash output) can be found much faster than brute-forcing a specific preimage. For an n-bit hash, the expected work to findanycollision is on the order of 2^(n/2), not 2^n.
The attack is relevant because many security constructions rely on collision resistance-digital signatures, certificate fingerprints, integrity checks, and some commitment schemes. If an attacker can generate two different documents with the same hash, they may trick a signer into signing one version while later presenting the other as "signed," depending on the protocol. Linear cryptanalysis and differential cryptanalysis are primarily techniques against block ciphers, analyzing relationships between plaintext/ciphertext differences or linear approximations across rounds. Algebraic attacks treat the cipher as a system of equations. The description "looking for different inputs that generate the same hash" is the hallmark of collision-finding, and the classic framing for that is the birthday attack.
NEW QUESTION # 25
(A security analyst is using 3DES for data encryption. Which 3DES key size is valid?)
- A. 112-bit
- B. 2,048-bit
- C. 128-bit
- D. 56-bit
Answer: A
Explanation:
3DES (Triple DES) applies the DES block cipher three times to increase effective security, and its commonly cited valid key sizes correspond to how many independent DES keys are used. Two-key
3DES uses two 56-bit DES keys (K1 and K2) in an EDE sequence (Encrypt with K1, Decrypt with K2, Encrypt with K1), yielding 112 bits of keying material (ignoring parity bits). Three-key 3DES uses three independent 56-bit keys for a total of 168 bits of keying material, but that option is not listed here.
A 56-bit key corresponds to single DES, not 3DES. 128-bit is associated with AES, not 3DES. 2,048-bit is typical for RSA keys, not symmetric ciphers. Therefore, among the choices provided, 112-bit is a valid 3DES key size. While 3DES is now deprecated for many uses due to its 64-bit block size and performance limitations, understanding its keying options remains important for legacy system assessment.
NEW QUESTION # 26
(Which cryptographic operation uses a single key?)
- A. Hashing
- B. Asymmetric
- C. Symmetric
- D. Padding
Answer: C
Explanation:
Symmetric cryptography uses a single shared secret key for both encryption and decryption. This contrasts with asymmetric cryptography, which uses a key pair (public/private). Symmetric algorithms (like AES, ChaCha20) are efficient and well-suited for bulk data encryption, but they require a secure method for key distribution because both parties must possess the same secret. Hashing is not a keyed operation by default (though HMAC is keyed); it maps arbitrary data to a fixed-size digest and is primarily used for integrity checking, fingerprints, and password hashing constructions. Padding is a data formatting technique (e.g., PKCS#7) used to align plaintext to a block size; it is not a cryptographic "operation" that uses a key. Therefore, the cryptographic operation characterized by using one key shared between parties is symmetric encryption. In real systems, symmetric encryption is frequently combined with asymmetric methods for key exchange and with MACs/AEAD for integrity, producing the standard hybrid approach used in protocols like TLS and IPsec.
NEW QUESTION # 27
(How often are transactions added to a blockchain?)
- A. Approximately every 30 minutes
- B. Approximately every 1 hour
- C. Approximately every 10 minutes
- D. Approximately every 24 hours
Answer: C
Explanation:
For Bitcoin, transactions are confirmed by inclusion in blocks, and the network targets an average block interval of about 10 minutes. That means transactions are "added" to the Bitcoin blockchain approximately every 10 minutes in the sense that a new block containing a batch of transactions is appended at that cadence. The 10-minute target is achieved by a difficulty adjustment mechanism that recalibrates mining difficulty roughly every 2016 blocks, aiming to keep the average interval stable despite changes in total network hash power. It is important to note that this is an average: blocks can be found faster or slower in the short term due to the probabilistic nature of proof-of-work mining.
Other blockchains have different block times (seconds to minutes), but the question's options and typical curriculum context align with Bitcoin's 10-minute design. Therefore, the correct choice is approximately every 10 minutes.
NEW QUESTION # 28
(What makes the RC4 cipher unique compared to RC5 and RC6?)
- A. Block
- B. Stream
- C. Symmetric
- D. Asymmetric
Answer: B
Explanation:
RC4 is unique among the RC family listed because it is a stream cipher. It generates a pseudorandom keystream and encrypts data by XORing that keystream with plaintext bytes (and decryption is the same XOR operation). This differs from RC5 and RC6, which are block ciphers: they encrypt fixed-size blocks of data through multiple rounds of operations (such as modular addition, XOR, and rotations) using a secret key. The stream-cipher design means RC4 historically fit protocols where data arrives continuously (e.g., early wireless and web encryption) and where simple, fast software implementation was desired. However, stream ciphers demand careful handling of nonces/IVs to avoid keystream reuse; reuse can catastrophically leak plaintext relationships. RC4 also has well-documented statistical biases in its keystream, leading to practical attacks in protocols like WEP and later concerns in TLS, which is why RC4 has been deprecated in modern security standards. Still, from a classification standpoint, "stream" is the distinguishing characteristic versus RC5/RC6 being block ciphers.
NEW QUESTION # 29
(What is an alternative to using a Certificate Revocation List (CRL) with certificates?)
- A. Online Certificate Status Protocol (OCSP)
- B. Policy Certificate Authority (CA)
- C. Root Certificate Authority (CA)
- D. Privacy Enhanced Mail (PEM)
Answer: A
Explanation:
OCSP is the primary online alternative to CRLs for checking whether a certificate has been revoked.
With a CRL, a relying party periodically downloads a list of revoked certificate serial numbers published by the issuing CA (or CRL distribution point). That approach can be bandwidth-heavy, introduces latency between revocation and client awareness, and can result in clients using stale revocation data if updates are infrequent. OCSP improves this by allowing a client (or a server on the client's behalf) to query an OCSP responder in near real time about the status of a specific certificate (good, revoked, or unknown). In practice, many TLS deployments use OCSP stapling, where the server periodically fetches a signed OCSP response from the CA's responder and "staples" it to the TLS handshake, reducing client-side network calls and improving privacy (the CA doesn't learn which site the client is visiting). Thus, OCSP provides a more timely, certificate-specific revocation status mechanism than CRLs while preserving the CA's signed assurance.
NEW QUESTION # 30
(What is an attribute of RC4 when used with WEP?)
- A. 128-bit key
- B. 40-bit key
- C. 512-bit key
- D. 256-bit key
Answer: B
Explanation:
In classic WEP deployments, RC4 was used with what is commonly called "40-bit WEP" (also labeled
"64-bit WEP" because it combines a 40-bit secret key with a 24-bit IV to form a 64-bit RC4 seed). The key attribute emphasized in many foundational descriptions of WEP is this 40-bit shared secret length, which was originally chosen due to export restrictions and legacy constraints. Although "104-bit WEP" (sometimes called "128-bit WEP," again counting the 24-bit IV) also existed, the option set here points to the historically standard and widely referenced attribute: a 40-bit key when RC4 is used in WEP.
Importantly, WEP's security failure is not only about key size; the 24-bit IV is too small and repeats frequently, and WEP's key scheduling vulnerabilities combined with IV reuse allow attackers to recover the secret key with enough captured frames. Still, among the given options, the correct attribute is the 40-bit key.
NEW QUESTION # 31
(What is the length (in bits) of a SHA-1 hash output?)
- A. 0
- B. 1
- C. 2
- D. 3
Answer: A
Explanation:
SHA-1 (Secure Hash Algorithm 1) produces a fixed-size output of 160 bits (20 bytes). Hash output size matters in cryptography because it influences collision resistance and the effort required for various attacks. For an ideal n-bit hash, finding a collision by generic means is expected around 2^(n/2) operations (birthday bound). With SHA-1's 160-bit output, that generic bound would be about 2^80, which was once considered strong; however, SHA-1 has been broken in practice with significantly less work due to cryptanalytic advances, and it is now deprecated for most security uses. Still, the question is strictly about output length, not current suitability. The other options do not match SHA-1: 40 bits would be far too small for a modern hash, 80 bits is not SHA-1's output, and 320 bits would imply a much larger digest (closer to SHA-256's 256 bits or SHA-384's 384 bits). Therefore, the correct SHA-1 output length is 160 bits.
NEW QUESTION # 32
(Which wireless security standard uses an authentication server with 802.1X and EAP?)
- A. WPA-Enterprise
- B. WPA-PSK
- C. WEP
- D. TKIP
Answer: A
Explanation:
802.1X is a port-based network access control framework that enables centralized authentication using an authentication server (commonly RADIUS). EAP (Extensible Authentication Protocol) runs within
802.1X to support many credential types (password-based methods like PEAP, certificate-based methods like EAP-TLS, and others). WPA-Enterprise is the wireless security mode that explicitly uses
802.1X + EAP with an authentication server to perform per-user/per-device authentication and to derive dynamic session keys. By contrast, WPA-PSK uses a pre-shared key without an external authentication server; all users share the same PSK, which is weaker for enterprise identity management. WEP is an older mechanism using static keys and does not provide modern 802.1X/EAP enterprise authentication in the WPA-Enterprise sense. TKIP is an encryption/integrity protocol used under WPA, not the full authentication "standard" involving an authentication server. Therefore, the correct choice is WPA-Enterprise.
NEW QUESTION # 33
(What is the RC4 encryption key size when utilizing WPA with Temporal Key Integrity Protocol (TKIP)?)
- A. 40 bits
- B. 56 bits
- C. 256 bits
- D. 128 bits
Answer: D
Explanation:
WPA with TKIP was designed as an interim improvement over WEP while still using the RC4 stream cipher for compatibility with legacy hardware. TKIP addresses WEP's major weaknesses by introducing per-packet key mixing, a message integrity mechanism ("Michael"), and replay protection.
In TKIP, the encryption key used with RC4 is 128 bits. Practically, TKIP derives a per-packet RC4 key from a 128-bit temporal key (TK), the transmitter's MAC address, and a sequence counter (TKIP Sequence Counter, TSC) to avoid the simple IV reuse patterns that made WEP easy to break. Even with these improvements, TKIP has known weaknesses and is deprecated in favor of WPA2/WPA3 using AES-based CCMP/GCMP. But strictly for the question asked, TKIP's RC4 keying material is based on a 128-bit key size, not 40/56-bit legacy sizes and not 256-bit.
NEW QUESTION # 34
(What is used to randomize the initial value when generating Initialization Vectors (IVs)?)
- A. Algorithm
- B. Plaintext
- C. Nonce
- D. Key
Answer: C
Explanation:
An IV (Initialization Vector) is a value used to ensure that encrypting identical plaintext under the same key produces different ciphertexts, preventing pattern leakage. In many secure designs, the IV must be unique (and often unpredictable) per encryption operation. A common way to ensure uniqueness is to incorporate a nonce-a "number used once." A nonce can be random, pseudo-random, or a counter-based value depending on the mode and security requirements. For example, CTR mode uses a nonce combined with a counter to produce unique input blocks; GCM uses a nonce/IV to ensure unique authentication and encryption behavior. The encryption key should remain stable across many operations and should not be used as the "randomizer" for IV generation; mixing key material into IV creation in an ad hoc way can create reuse or correlation issues. Plaintext and algorithm do not provide the needed uniqueness property. The nonce concept is specifically about ensuring one-time uniqueness of the starting value so that IV reuse does not repeat keystream blocks (stream modes) or reveal plaintext equality (CBC/CTR). Therefore, the correct choice is Nonce.
NEW QUESTION # 35
(What describes how Counter (CTR) mode encryption functions?)
- A. Uses a self-synchronizing stream cipher where the IV is encrypted and XORed with the data stream one bit at a time
- B. Encrypts each block with the same key, where each block is independent of the others
- C. Uses an IV to encrypt the first block, then uses the result of the encryption to encrypt the next block
- D. Converts the block cipher into a stream cipher, then uses a counter value and a nonce to encrypt the data
Answer: D
Explanation:
CTR mode turns a block cipher (like AES) into a stream-like construction by generating a keystream from successive encryptions of a changing input block. Specifically, CTR forms input blocks using a nonce (unique per message) combined with an increasing counter. Each nonce||counter block is encrypted with the block cipher under the shared key, producing a pseudorandom output block. That output is then XORed with plaintext to yield ciphertext (and XORed with ciphertext to recover plaintext). This design enables parallelization (blocks can be generated independently), efficient random access decryption, and avoids chaining dependencies seen in modes like CBC. Option B describes CFB-like behavior; option C describes ECB; option D describes CBC. CTR's security critically depends on never reusing the same nonce/counter sequence with the same key, because reuse would repeat keystream blocks and expose plaintext relationships. Therefore, the correct description is that CTR converts the block cipher into a stream cipher using a counter value and a nonce.
NEW QUESTION # 36
(Which attack may take the longest amount of time to achieve success?)
- A. Birthday
- B. Brute-force
- C. Dictionary
- D. Rainbow table
Answer: B
Explanation:
A brute-force attack exhaustively tries every possible key or password candidate until the correct one is found. Because it explores the full search space (or a very large portion of it), brute force is often the slowest method, especially when strong keys, long passwords, rate limits, and slow password hashing (bcrypt/Argon2) are used. By contrast, a dictionary attack reduces work by trying only common or likely passwords, often succeeding quickly against weak human-chosen secrets. Rainbow table attacks shift work into precomputation; once a table exists, lookup can be faster than brute-force-though salt and modern hashing defeat them. Birthday attacks are about finding collisions, not necessarily recovering a specific secret, and their expected work is about 2^(n/2) for an n-bit hash, which can be less than brute-force key search in many contexts. Therefore, among the listed options, brute-force generally takes the longest to succeed because it makes the fewest assumptions and does the most total work.
NEW QUESTION # 37
(Which authentication method allows a customer to authenticate to a web service?)
- A. End-to-end authentication
- B. Mutual authentication
- C. One-way client authentication
- D. One-way server authentication
Answer: C
Explanation:
One-way client authentication is the method where the client (customer) proves its identity to the server (web service). In cryptographic terms, this is commonly implemented through client credentials such as client TLS certificates (mTLS from the server's perspective) or through authentication protocols layered over TLS (for example, signed tokens), but the defining direction is that the client is the party being authenticated. In a strict TLS certificate-authentication framing, client authentication occurs when the server requests a client certificate during the handshake and the client demonstrates possession of the corresponding private key (via signature in handshake messages). The server then validates the client certificate chain and authorization policy. One-way server authentication, by contrast, authenticates only the server to the client and does not identify the customer. Mutual authentication authenticates both sides simultaneously; while it includes client authentication, it is broader than what the question asks. "End-to-end authentication" describes assurance between endpoints across intermediaries, but it is not the specific "customer authenticates to service" method in certificate-based terminology. Therefore, the best answer is one-way client authentication.
NEW QUESTION # 38
(Which symmetric encryption technique uses a 256-bit key size and a 128-bit block size?)
- A. IDEA
- B. 3DES
- C. DES
- D. AES
Answer: D
Explanation:
AES (Advanced Encryption Standard) is a symmetric block cipher standardized to operate on a fixed
128-bit block size and supports key sizes of 128, 192, and 256 bits. When the key size is 256 bits, the cipher is commonly referred to as AES-256, but the block size remains 128 bits regardless of key length.
This combination (256-bit key, 128-bit block) matches the question precisely. By comparison, DES uses a 64-bit block size with a 56-bit effective key. 3DES also uses a 64-bit block size and effectively applies DES three times, yielding an effective key length typically cited as 112 bits (two-key 3DES) or 168 bits (three-key 3DES), depending on how keys are configured. IDEA uses a 64-bit block size with a 128-bit key. Therefore, the only listed algorithm that supports a 256-bit key while maintaining a 128-bit block size is AES. This is one reason AES is widely adopted for modern symmetric encryption: strong key sizes with efficient implementation and broad standardization.
NEW QUESTION # 39
(Which number generator has different results given the same input data?)
- A. Pseudorandom
- B. Sequence
- C. True random
- D. Prime
Answer: C
Explanation:
A true random number generator (TRNG) produces outputs derived from nondeterministic physical processes (e.g., thermal noise, oscillator jitter, radioactive decay, or other hardware entropy sources).
Because the underlying phenomenon is not algorithmically determined by an input seed in the same way as a PRNG, repeated "inputs" (or identical conditions from a software perspective) do not yield the same sequence; the outputs vary unpredictably. By contrast, a pseudorandom number generator (PRNG) is deterministic: given the same seed and internal state, it produces the same output sequence, which is useful for repeatability but means security depends on seed secrecy and proper seeding.
"Prime" is not a generator type, and "sequence" is too generic and does not imply nondeterminism. In cryptographic systems, TRNGs (or hardware entropy sources) are often used to seed cryptographically secure PRNGs (CSPRNGs), combining high-quality entropy with efficient generation. Therefore, the generator that can produce different results for the "same input data" is a true random number generator.
NEW QUESTION # 40
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