A fully updated 2026 Introduction-to-Cryptography Exam Dumps exam guide from training expert 2Pass4sure
Provides complete coverage of every objective on exam and exam preparation Introduction-to-Cryptography
NEW QUESTION # 20
(Which authentication method allows a customer to authenticate to a web service?)
- A. One-way server authentication
- B. One-way client authentication
- C. End-to-end authentication
- D. Mutual authentication
Answer: B
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 # 21
(Why did the National Institute of Standards and Technology (NIST) choose Ascon for lightweight cryptography?)
- A. To encrypt data at rest
- B. To ensure compatibility with legacy systems
- C. To provide a secure and efficient encryption solution for resource-constrained devices
- D. To authenticate users during data transmission
Answer: C
Explanation:
NIST's lightweight cryptography effort targets environments like IoT and embedded systems where CPU, memory, energy, and bandwidth are constrained, yet strong security is still required. Ascon is an authenticated encryption with associated data (AEAD) family designed to be efficient in both hardware and software with small footprint, making it well-suited for constrained devices. NIST selected Ascon because it offers a strong security design with good performance and implementability under tight resource budgets, while providing modern protections (confidentiality + integrity) through AEAD. That aligns with option C: secure and efficient encryption for resource-constrained devices. The selection was not primarily about authenticating users (that is typically handled by protocols and identity systems, not an AEAD primitive). It was also not mainly about legacy compatibility; lightweight cryptography aims at new and constrained deployments rather than preserving outdated stacks. And while Ascon can certainly be used to protect data at rest, that is only one application; the core reason for the choice is its suitability for constrained environments and robust, efficient authenticated encryption.
NEW QUESTION # 22
(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. Privacy Enhanced Mail (PEM)
- D. Root Certificate Authority (CA)
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 # 23
(Why is it important for cryptography frameworks to adapt over time?)
- A. To maintain a rigid structure for data protection
- B. To standardize the use of obsolete encryption techniques
- C. To respond to emerging security threats and vulnerabilities
- D. To comply with outdated technology standards
Answer: C
Explanation:
Cryptography must evolve because threats, computing capabilities, and attack techniques continuously change. Algorithms once considered safe can become vulnerable due to cryptanalysis, implementation attacks, protocol flaws, or sheer increases in available compute power. Examples include the deprecation of SHA-1 for signatures, weakening of RC4, and migration away from older TLS versions and weak cipher suites. Frameworks also need to adapt to new environments-cloud architectures, IoT deployments, mobile devices-and new adversary models, including the long-term risk posed by quantum computing to current public-key systems. Adaptation includes updating standards, increasing key sizes where needed, adopting modern primitives (AEAD modes, stronger KDFs), improving key management practices (rotation, hardware- backed storage), and refining operational guidance (certificate lifetimes, revocation strategies). A rigid structure that never changes would lock organizations into obsolete protections and accumulate risk.
Standardizing obsolete techniques or complying with outdated standards is the opposite of sound security engineering. Therefore, cryptography frameworks must adapt over time to respond to emerging threats and vulnerabilities and to maintain effective protection as the landscape evolves.
NEW QUESTION # 24
(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 cloud provider and the seller
- B. The buyer and the Federal Trade Commission
- C. The Federal Trade Commission and the cloud provider
- D. The seller and the buyer
Answer: D
NEW QUESTION # 25
(A security engineer is implementing device authentication as a form of two-factor authentication in a Public Key Infrastructure (PKI) environment. What should be used as a second form of authentication?)
- A. Digital signature
- B. Asymmetric encryption
- C. Symmetric encryption
- D. Digital certificate
Answer: D
Explanation:
In a PKI environment, a digital certificate is the standard credential used to bind an identity (user, device, service) to a public key, with that binding vouched for by a Certificate Authority. For device authentication, the device typically proves possession of the private key corresponding to the certificate' s public key (for example, during a TLS handshake). As a second factor in a two-factor model, a certificate (often stored in a TPM, smart card, or secure enclave) represents "something you have"-a cryptographic credential anchored to hardware or a managed endpoint. The other listed options (symmetric encryption, asymmetric encryption, digital signature) are cryptographic operations or algorithm classes, not stand-alone authentication factors. A digital signature is a mechanism used within authentication flows, but it is not itself the credential that establishes an enrolled device identity within PKI. In practice, a certificate-based device factor is commonly paired with a knowledge factor (password/PIN) or a biometric factor to achieve true 2FA, but among these choices, the appropriate second form of authentication in PKI terms is the digital certificate.
NEW QUESTION # 26
(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 # 27
(What is the length of the Initialization Vector (IV) in WEP?)
- A. 24 bits
- B. 48 bits
- C. 40 bits
- D. 56 bits
Answer: A
Explanation:
WEP (Wired Equivalent Privacy) uses the RC4 stream cipher and combines a per-packet Initialization Vector (IV) with a shared secret key to form the RC4 seed for that packet's keystream. The IV in WEP is 24 bits long and is transmitted in the clear as part of the 802.11 frame so the receiver can reconstruct the same per-packet RC4 key stream. The short IV space (2²# possible values) is a major design weakness: on a busy network, IVs repeat frequently, causing keystream reuse. Because RC4 is a stream cipher, keystream reuse enables attackers to derive relationships between plaintexts and recover keys with statistical attacks (notably the Fluhrer, Mantin, and Shamir (FMS) family of attacks and related improvements). WEP also uses a CRC-32 integrity check (ICV) that is not cryptographically strong and is vulnerable to modification attacks. The 24-bit IV length is therefore a key reason WEP is considered insecure and has been replaced by WPA/WPA2 mechanisms that use stronger key mixing, larger nonces/IVs, and robust integrity protection.
NEW QUESTION # 28
(Which cipher uses shifting letters of the alphabet for encryption?)
- A. Vigenere
- B. Bifid
- C. SHA-1
- 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 # 29
(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 cloud provider and the seller
- B. The buyer and the Federal Trade Commission
- 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 # 30
(Which cryptographic technique is used to ensure data integrity?)
- A. Non-repudiation
- B. Steganography
- C. Authentication
- D. Digital signatures
Answer: D
Explanation:
Data integrity means ensuring that information has not been modified without authorization. Digital signatures are a core cryptographic technique that provides integrity by binding a message (typically its hash) to the signer's private key. The signer creates a signature over the message digest; the verifier checks it with the signer's public key and recomputes the digest. Any change to the message alters the digest and causes verification to fail, revealing tampering. Digital signatures also support authenticity (verifying the signer) and can contribute to nonrepudiation under proper key-management and policy controls, but integrity is a primary guarantee they deliver. "Authentication" is broader and can be achieved by other means, but it is not as directly tied to integrity as signatures in this option set. "Non-repudiation" is an outcome/goal rather than a standalone integrity technique. "Steganography" hides the existence of data and does not inherently protect integrity. Therefore, among these options, digital signatures are the best cryptographic technique for ensuring data integrity.
NEW QUESTION # 31
(What is the purpose of code-signing in current systems?)
- A. To compress data for efficient storage
- B. To verify the integrity and authenticity of software
- C. To authenticate users during data transmission
- D. To generate random numbers for encryption
Answer: B
Explanation:
Code-signing is used to provide verifiable assurance that software comes from a known publisher and has not been modified since it was signed. In a typical code-signing workflow, the publisher computes a cryptographic hash (digest) of the executable or package and then creates a digital signature over that digest using the publisher's private key. Operating systems, browsers, and application platforms verify the signature using the corresponding public key (usually delivered via a code-signing certificate chained to a trusted root).
If verification succeeds, the system can trust that the code's contents match what the publisher signed (integrity) and that the signer identity is authenticated by the certificate chain (authenticity). This helps defend against tampering, malware injection, and supply-chain attacks where attackers alter binaries or updates in transit or at rest. Code-signing does not primarily generate randomness, compress data, or authenticate users; it authenticates the software publisher and validates the software artifact. Modern ecosystems also use timestamping and revocation checking to handle certificate expiration and compromised signing keys, reinforcing trust over time.
NEW QUESTION # 32
(Which wireless security standard uses an authentication server with 802.1X and EAP?)
- A. WPA-Enterprise
- B. WPA-PSK
- C. TKIP
- D. WEP
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
(A security analyst uses a polyalphabetic substitution cipher with a keyword of YELLOW to encrypt a message. Which cipher should be used to encrypt the message?)
- A. Caesar
- B. Vigenere
- C. Playfair
- D. Pigpen
Answer: B
Explanation:
A polyalphabetic substitution cipher uses multiple substitution alphabets rather than a single fixed mapping.
The classic cipher that uses a keyword to select shifting alphabets across the message is the Vigenere cipher.
In Vigenere, each plaintext letter is shifted by an amount determined by the corresponding key letter (repeating the keyword as needed). For example, a keyword like "YELLOW" is aligned under the plaintext; each key character defines a Caesar shift (A=0, B=1, ...) applied to the plaintext character, producing ciphertext. This rotation of alphabets across positions makes Vigenere more resistant to simple frequency analysis than monoalphabetic substitution, because the same plaintext letter may encrypt to different ciphertext letters depending on its position relative to the key. The Pigpen cipher is a symbol substitution cipher, Caesar is monoalphabetic with a single shift, and Playfair is a digraph substitution cipher using a 5×5 key square, not the repeating-key polyalphabetic method described. Therefore, the correct cipher is Vigenere.
NEW QUESTION # 34
(Which type of exploit involves looking for different inputs that generate the same hash?)
- A. Differential cryptanalysis
- B. Birthday attack
- C. Algebraic attack
- D. Linear cryptanalysis
Answer: B
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 # 35
(Which is a primary reason for ethical concerns about encryption?)
- A. It complicates government access to potentially crucial information.
- B. It only benefits large corporations.
- C. It reduces data storage requirements.
- D. It provides faster data transmission.
Answer: A
Explanation:
Ethical concerns about encryption commonly arise from the tension between individual privacy/security and societal needs such as law enforcement, national security, and public safety. Strong end-to-end encryption can prevent unauthorized parties from accessing data, including criminals and foreign adversaries, but it can also limit legitimate government access to communications and evidence-even with warrants-because providers may not possess the keys needed to decrypt. This has fueled debates around "going dark," lawful access, and proposals for exceptional access mechanisms or backdoors. Critics argue that weakening encryption for access would create systemic risk, since any intentional vulnerability can be exploited by malicious actors, while proponents emphasize investigative needs in serious cases. Regardless of the stance, the primary ethical concern reflected in policy debates is that encryption complicates government access to information that may be crucial for preventing or investigating crime. The other options do not capture the main ethical controversy: encryption is widely beneficial beyond corporations, and it is not primarily about speed or storage reduction. Therefore, the correct answer is B.
NEW QUESTION # 36
(Why are large prime numbers important in cryptography?)
- A. They make decryption easier.
- B. They make encryption faster.
- C. They are used for encoding messages.
- D. They provide security in encryption algorithms.
Answer: D
Explanation:
Large prime numbers are crucial because they enable cryptosystems where certain operations are easy to perform, but reversing them is computationally hard without secret information. In RSA, security is based on the difficulty of factoring a large composite number that is the product of two large primes; multiplying primes is easy, but factoring the product is believed to be hard at sufficient sizes. In Diffie-Hellman and related systems, primes define finite groups (often modulo a large prime) where exponentiation is efficient but the discrete logarithm problem is hard. Primes also help ensure desirable group properties-such as having a large cyclic subgroup-reducing vulnerabilities from small subgroups or weak structure. The value of "large" is that it makes brute-force and known algorithmic attacks infeasible with current computing resources. Large primes do not primarily make encryption faster, nor do they make decryption easier; they are chosen to maximize security margins. While primes can be involved in encoding steps, their importance is security: they form the mathematical foundation for hardness assumptions used by major public-key algorithms. Therefore, the best answer is that they provide security in encryption algorithms.
NEW QUESTION # 37
(What is the value of 51 mod 11?)
- A. 04
- B. 07
- C. 0
- D. 05
Answer: B
Explanation:
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.
NEW QUESTION # 38
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