CCNA Cryptography Questions

Multi-Selectmedium

A security team is implementing a PKI for a large enterprise. Which TWO of the following are commonly used methods for certificate revocation checking? (Select TWO.)

Select 2 answers

A.Certificate Signing Request (CSR)

B.Online Certificate Status Protocol (OCSP)

C.Certificate Revocation List (CRL)

D.Key Escrow

E.Digital Signature Algorithm (DSA)

AnswersB, C

OCSP provides real-time status.

Why this answer

CRL (Certificate Revocation List) and OCSP (Online Certificate Status Protocol) are the two primary methods.

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MCQmedium

A company is deploying a VPN using IPsec. They want to ensure that even if the private key of the server is compromised, past session keys cannot be derived. Which key exchange method should they use?

A.Pre-shared key (PSK)

B.RSA key exchange

C.Ephemeral Diffie-Hellman (DHE or ECDHE)

D.Diffie-Hellman with static keys

AnswerC

Ephemeral key exchange ensures that session keys are temporary and not linked to long-term keys.

Why this answer

Ephemeral Diffie-Hellman (DHE or ECDHE) provides perfect forward secrecy (PFS) because it generates a unique, temporary session key for each session using ephemeral key pairs. Even if the server's long-term private key is compromised, past session keys cannot be derived because they were created from ephemeral keys that are discarded after each session. This ensures that historical encrypted traffic remains secure.

Exam trap

The trap here is that candidates confuse authentication with key exchange, assuming that RSA or static DH provides PFS because they involve public-key cryptography, but only ephemeral DH ensures that session keys are not derived from long-term secrets.

How to eliminate wrong answers

Option A is wrong because pre-shared keys (PSK) are static and do not provide PFS; if the PSK is compromised, all past session keys can be derived. Option B is wrong because RSA key exchange uses the server's static private key to encrypt the session key, so compromising that private key allows decryption of all past session keys. Option D is wrong because Diffie-Hellman with static keys uses long-term Diffie-Hellman keys that do not change per session, so compromising the static private key enables recovery of all past session keys.

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MCQmedium

An organization is migrating from 3DES to AES-256 for encrypting data at rest. Which mode of AES is recommended for authenticated encryption?

A.ECB

B.GCM

C.CBC

D.CTR

AnswerB

GCM combines CTR mode with authentication tags, providing both confidentiality and integrity.

Why this answer

GCM (Galois/Counter Mode) is the correct choice because it provides both confidentiality and authenticity in a single, efficient mode. For data at rest, authenticated encryption ensures that encrypted data cannot be tampered with undetected, which is critical for integrity. AES-256-GCM is widely recommended and standardized (NIST SP 800-38D) for this purpose.

Exam trap

ISC2 SSCP often tests the misconception that any mode providing confidentiality (like CBC or CTR) is sufficient for secure encryption, but the trap here is that authenticated encryption specifically requires a mode that also guarantees integrity, which only GCM (or CCM) provides among the listed options.

How to eliminate wrong answers

Option A is wrong because ECB (Electronic Codebook) mode encrypts each block independently, producing identical ciphertext for identical plaintext blocks, which leaks patterns and provides no authentication. Option C is wrong because CBC (Cipher Block Chaining) mode provides only confidentiality, not authentication; it requires a separate MAC (e.g., HMAC) to achieve authenticated encryption, and it is vulnerable to padding oracle attacks if not implemented carefully. Option D is wrong because CTR (Counter) mode provides only confidentiality and no integrity protection; it is a stream cipher mode that can be combined with a MAC but does not itself offer authenticated encryption.

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MCQmedium

Which of the following protocols is used to securely transfer files over SSH and is considered a replacement for FTP?

A.IPsec

B.HTTPS

C.SFTP

D.SMTPS

AnswerC

SFTP is correct.

Why this answer

SFTP (SSH File Transfer Protocol) provides secure file transfer over SSH.

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MCQmedium

An organization is implementing a digital signature solution to ensure non-repudiation of documents. Which combination of keys is used during the signing process?

A.Recipient's public key to sign, recipient's private key to verify

B.Sender's private key to sign, sender's public key to verify

C.Sender's public key to sign, recipient's private key to verify

D.A shared symmetric key for both signing and verification

AnswerB

The private key creates the signature, and the corresponding public key verifies it.

Why this answer

Digital signatures use asymmetric cryptography where the sender creates a signature with their private key, and the recipient verifies it with the sender's public key. This ensures non-repudiation because only the sender possesses their private key, so they cannot deny having signed the document. The process typically involves hashing the document and encrypting the hash with the sender's private key.

Exam trap

ISC2 SSCP often tests the misconception that signing uses a public key or that verification uses a private key, leading candidates to confuse the roles of keys in encryption versus signing.

How to eliminate wrong answers

Option A is wrong because the recipient's public key is used for encrypting messages to the recipient, not for signing; signing requires the sender's private key, and verification uses the sender's public key, not the recipient's private key. Option C is wrong because the sender's public key cannot sign (signing requires a private key), and the recipient's private key is never used for verification of a sender's signature. Option D is wrong because symmetric keys do not provide non-repudiation; they are shared secrets and cannot uniquely tie a signature to a single sender, as both parties possess the same key.

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MCQhard

A certificate authority (CA) issues a certificate with the extended key usage (EKU) extension specifying 'serverAuth'. Which of the following is this certificate allowed to do?

A.Encrypt email

B.Authenticate a TLS server

C.Sign code

D.Issue subordinate CA certificates

AnswerB

The serverAuth EKU is specifically for TLS server authentication.

Why this answer

The Extended Key Usage (EKU) extension specifies the intended purpose of a certificate. The 'serverAuth' OID (1.3.6.1.5.5.7.3.1) explicitly permits the certificate to be used for authenticating a TLS server during the SSL/TLS handshake, such as in HTTPS. This is defined in RFC 5280 and is enforced by TLS clients to ensure the certificate is used only for its designated purpose.

Exam trap

A common pitfall is assuming that a certificate with 'serverAuth' can also be used for client authentication or other purposes, but the EKU extension strictly limits usage. Candidates often confuse 'serverAuth' with other EKUs like 'clientAuth' or 'emailProtection'.

How to eliminate wrong answers

Option A is wrong because encrypting email requires the 'emailProtection' EKU (1.3.6.1.5.5.7.3.4), not 'serverAuth'. Option C is wrong because signing code requires the 'codeSigning' EKU (1.3.6.1.5.5.7.3.3), which is a separate purpose. Option D is wrong because issuing subordinate CA certificates requires the 'keyCertSign' key usage extension and often the 'CA:TRUE' basic constraint, not the 'serverAuth' EKU; 'serverAuth' is for end-entity certificates, not for CA certificates.

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MCQmedium

An organization wants to implement a key exchange mechanism that provides forward secrecy. Which of the following should be used?

A.Pre-shared key

B.Ephemeral Diffie-Hellman

C.RSA key exchange

D.Static Diffie-Hellman

AnswerB

Ephemeral DH provides forward secrecy.

Why this answer

Ephemeral Diffie-Hellman (DHE or ECDHE) provides forward secrecy because the session keys are ephemeral and not derived from long-term keys.

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MCQhard

An organization is configuring a VPN using IPsec. To ensure forward secrecy, which key exchange method should be used?

A.Ephemeral Diffie-Hellman (DHE or ECDHE)

B.RSA key exchange

C.Pre-shared key (PSK)

D.Static Diffie-Hellman

AnswerA

Ephemeral DH generates new key pairs for each session, so compromise of long-term keys does not expose past session keys.

Why this answer

Ephemeral Diffie-Hellman (DHE or ECDHE) provides forward secrecy because it generates a temporary, one-time key pair for each session. If the long-term private key is compromised, past session keys cannot be derived, as the ephemeral keys are discarded after use. This ensures that even if an attacker records encrypted traffic and later obtains the private key, they cannot decrypt past sessions.

Exam trap

The trap here is that candidates often confuse 'Diffie-Hellman' in general with forward secrecy, not realizing that only the ephemeral variant (DHE/ECDHE) provides it, while static Diffie-Hellman does not.

How to eliminate wrong answers

Option B (RSA key exchange) is wrong because RSA uses the server's static private key to encrypt the pre-master secret; if the private key is later compromised, all past session keys can be decrypted, providing no forward secrecy. Option C (Pre-shared key (PSK)) is wrong because PSK relies on a static shared secret that does not change per session; if the PSK is compromised, all past and future sessions can be decrypted. Option D (Static Diffie-Hellman) is wrong because it uses fixed, long-term Diffie-Hellman keys that do not change per session; compromise of the static private key allows an attacker to derive all past session keys, violating forward secrecy.

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MCQeasy

Which of the following is a method to check the revocation status of a digital certificate in real-time without the client downloading a full list?

A.Certificate Revocation List (CRL)

B.Self-signed certificate validation

C.Online Certificate Status Protocol (OCSP)

D.Certificate Transparency (CT)

AnswerC

OCSP provides real-time revocation status for individual certificates.

Why this answer

OCSP allows querying the CA's responder for the status of a specific certificate in real-time.

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Multi-Selectmedium

A company is migrating from 3DES to a modern encryption algorithm. Which of the following are acceptable choices? (Select TWO)

Select 2 answers

A.DES

B.ChaCha20

C.AES

D.RC4

E.Blowfish

AnswersB, C

ChaCha20 is a modern stream cipher, considered secure and efficient.

Why this answer

AES and ChaCha20 are modern symmetric ciphers considered secure. RC4 is broken, Blowfish is older (64-bit block), and DES is obsolete.

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MCQhard

Which of the following best describes the difference between HMAC and a simple hash function like SHA-256 when used for message authentication?

A.HMAC is faster than SHA-256

B.SHA-256 produces a larger digest than HMAC

C.HMAC provides integrity and authentication; SHA-256 provides only integrity

D.HMAC is used for encryption, not hashing

AnswerC

Correct: HMAC uses a key for authentication.

Why this answer

HMAC incorporates a secret key into the hash process, providing authentication that a simple hash cannot.

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MCQmedium

A company is implementing a PKI for internal use. What is the primary purpose of a Certificate Revocation List (CRL)?

A.To validate certificate chains

B.To encrypt certificate requests

C.To store all issued certificates

D.To publish revoked certificates

AnswerD

CRLs list certificates that have been revoked and should no longer be trusted.

Why this answer

The primary purpose of a Certificate Revocation List (CRL) is to publish a list of certificates that have been revoked by the Certificate Authority (CA) before their scheduled expiration. This allows relying parties to verify that a certificate is still valid and has not been compromised, ensuring trust in the PKI.

Exam trap

The trap here is that candidates confuse the CRL's purpose with certificate validation or storage, mistakenly thinking it validates chains or stores all certificates, when in fact it only publishes revoked certificates for status checking.

How to eliminate wrong answers

Option A is wrong because validating certificate chains is performed using the CA's public key and checking signatures, not by consulting a CRL; CRLs are used only to check revocation status. Option B is wrong because encrypting certificate requests is the role of protocols like PKCS#10 or CMP, not the CRL, which is a signed list of revoked certificates. Option C is wrong because storing all issued certificates is the function of a certificate repository or database, whereas a CRL only contains certificates that have been revoked, not all issued ones.

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MCQmedium

An organization is moving away from legacy encryption and wants to avoid stream ciphers due to known vulnerabilities. Which of the following algorithms should be avoided because it is a stream cipher with known weaknesses like the BEAST attack?

A.RC4

B.3DES

C.AES-GCM

D.ChaCha20

AnswerA

RC4 is the deprecated stream cipher.

Why this answer

RC4 is a stream cipher with known weaknesses, such as biases in its output stream that can lead to plaintext recovery attacks. Although the BEAST attack actually exploits CBC mode in TLS 1.0, RC4 was often used as a workaround; however, RC4 itself has inherent vulnerabilities, making it unsuitable for secure encryption. Since the organization wants to avoid stream ciphers due to such vulnerabilities, RC4 should be avoided.

Exam trap

The trap here is that candidates may assume all stream ciphers are equally vulnerable, but ChaCha20 is a modern, secure stream cipher, while RC4 is the specific one with known weaknesses like BEAST.

How to eliminate wrong answers

Option B (3DES) is wrong because 3DES is a block cipher, not a stream cipher, and while it is deprecated due to slow performance and small block size, it is not associated with the BEAST attack. Option C (AES-GCM) is wrong because AES-GCM is a block cipher operating in Galois/Counter Mode, which is an authenticated encryption mode and not a stream cipher; it is not vulnerable to BEAST. Option D (ChaCha20) is wrong because ChaCha20 is a stream cipher, but it is modern, secure, and not associated with the BEAST attack; it is actually recommended as a replacement for RC4.

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MCQmedium

A security analyst is evaluating the cryptographic settings for a new application that requires both confidentiality and integrity for data in transit. The analyst needs to choose a symmetric cipher that provides authenticated encryption. Which of the following is the best choice?

A.RC4 stream cipher

B.AES in ECB mode

C.AES in GCM mode

D.AES in CBC mode

AnswerC

GCM mode provides both confidentiality and integrity (authenticated encryption) using a counter mode for encryption and a Galois field for authentication.

Why this answer

AES in GCM mode provides both encryption and authentication, making it the preferred choice for authenticated encryption. ECB lacks diffusion and is insecure, CBC provides only encryption, and RC4 is a broken stream cipher.

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MCQmedium

In X.509 certificate format, which field is used to specify the fully qualified domain name(s) for which the certificate is valid?

A.Key Usage

B.Issuer

C.Subject

D.Subject Alternative Name

AnswerD

SAN is the correct field.

Why this answer

The Subject Alternative Name (SAN) extension allows specifying multiple hostnames.

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Multi-Selecthard

An organization is designing a secure email system using S/MIME. Which of the following are essential components of the PKI that must be in place? (Select THREE)

Select 3 answers

A.A symmetric key distribution center (KDC)

B.X.509 digital certificates for each user

C.A method to check certificate revocation (e.g., CRL or OCSP)

D.A timestamp authority (TSA)

E.A certificate authority (CA) to sign certificates

AnswersB, C, E

Each user needs a certificate containing their public key and identity.

Why this answer

S/MIME relies on a PKI where each user possesses an X.509 digital certificate that binds their identity to a public key. This certificate is essential for signing and encrypting emails, as it allows recipients to verify the sender's identity and encrypt messages using the sender's public key.

Exam trap

In the SSCP exam, candidates often mistakenly select a KDC or TSA as essential for S/MIME, but these are auxiliary services, not core PKI components.

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MCQmedium

A security analyst is reviewing a digital signature implementation. The signer uses their private key to encrypt the hash of a message. What does the recipient use to verify the signature?

A.The recipient's private key

B.The signer's private key

C.The recipient's public key

D.The signer's public key

AnswerD

The signer's public key is used to verify the signature by decrypting the hash.

Why this answer

Digital signatures use asymmetric cryptography where the signer encrypts the message hash with their private key. The recipient decrypts that encrypted hash using the signer's public key, then compares it to a locally computed hash of the received message. If they match, the signature is verified, proving both authenticity and integrity.

Exam trap

Candidates often confuse the roles of keys in digital signatures, mistakenly thinking the recipient uses their own private key or the signer's private key for verification. In asymmetric cryptography, signature verification always uses the signer's public key.

How to eliminate wrong answers

Option A is wrong because the recipient's private key is used for decryption of data encrypted with the recipient's public key, not for verifying a signature from another party. Option B is wrong because the signer's private key is kept secret and used only by the signer to create the signature; sharing it would compromise the entire system. Option C is wrong because the recipient's public key is used by others to encrypt data for the recipient, not to verify a signature created by a different entity.

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MCQhard

A security auditor reviews a system that uses HMAC-SHA256 for message authentication. Which property does HMAC provide that a simple hash of the message does not?

A.Confidentiality

B.Non-repudiation

C.Integrity and authentication using a shared secret

D.Forward secrecy

AnswerC

HMAC ensures the message has not been altered and verifies the sender's possession of the secret key.

Why this answer

HMAC-SHA256 uses a shared secret key combined with the message before hashing, which provides both integrity (detecting tampering) and authentication (verifying the sender knows the secret). A simple hash of the message alone offers integrity but no authentication, because anyone can compute the same hash without a secret. Thus, HMAC adds authentication via the shared secret, making option C correct.

Exam trap

The trap here is that candidates confuse integrity (provided by any hash) with authentication (which requires a shared secret), leading them to think a simple hash is sufficient for message authentication, but HMAC specifically adds the keyed property.

How to eliminate wrong answers

Option A is wrong because HMAC does not provide confidentiality; it does not encrypt the message, only authenticates it. Option B is wrong because non-repudiation requires asymmetric cryptography (e.g., digital signatures) to bind a message to a specific entity, whereas HMAC uses a shared symmetric key and cannot prove which party created it. Option D is wrong because forward secrecy is a property of key exchange protocols (e.g., Diffie-Hellman ephemeral) that ensures session keys are not compromised if long-term keys are leaked; HMAC does not provide forward secrecy.

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MCQmedium

Which of the following best describes the purpose of a Hardware Security Module (HSM) in key management?

A.To store cryptographic keys in a secure, tamper-resistant environment

B.To replace public key infrastructure (PKI)

C.To accelerate network traffic encryption

D.To generate random numbers for non-cryptographic use

AnswerA

HSMs are designed to protect keys throughout their lifecycle.

Why this answer

A Hardware Security Module (HSM) is a dedicated, tamper-resistant hardware appliance designed to securely generate, store, and manage cryptographic keys throughout their lifecycle. By keeping keys within the HSM's physical and logical boundaries, it prevents unauthorized extraction even if the host system is compromised, which is the core purpose of an HSM in key management.

Exam trap

The trap here is that candidates confuse an HSM's ability to perform cryptographic operations (like encryption or signing) with its primary purpose, which is secure key storage and lifecycle management, not performance acceleration or replacing PKI.

How to eliminate wrong answers

Option B is wrong because an HSM does not replace Public Key Infrastructure (PKI); PKI is a framework of policies, roles, and software (e.g., Certificate Authorities) for managing digital certificates, while an HSM is a hardware device that can be used to protect the private keys within a PKI. Option C is wrong because accelerating network traffic encryption is not the primary purpose of an HSM; that function is typically performed by dedicated cryptographic accelerators or offload engines (e.g., Intel QAT), whereas an HSM focuses on secure key storage and limited cryptographic operations. Option D is wrong because while HSMs can generate random numbers, they are used for cryptographic purposes (e.g., key generation, nonces) and not for non-cryptographic use; general random number generation for non-cryptographic tasks is done by simpler PRNGs like those in standard OS libraries.

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MCQeasy

Which of the following hash algorithms is considered cryptographically broken and should be avoided due to collision attacks?

A.SHA-3

B.SHA-256

C.MD5

D.HMAC-SHA256

AnswerC

MD5 is broken and collisions can be generated easily.

Why this answer

MD5 is known to have collision vulnerabilities and is no longer considered secure.

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MCQmedium

A security engineer needs to choose an asymmetric algorithm for a system with limited computational resources, such as an IoT device. The algorithm must provide equivalent security to RSA 2048-bit while using smaller key sizes. Which algorithm should they choose?

A.RSA with 2048-bit keys

B.Elliptic Curve Cryptography (ECC) with 256-bit keys

C.Diffie-Hellman with 2048-bit keys

D.3DES with 168-bit keys

AnswerB

ECC provides strong security with smaller keys, ideal for IoT.

Why this answer

Elliptic Curve Cryptography (ECC) with 256-bit keys provides equivalent security to RSA 2048-bit because the elliptic curve discrete logarithm problem is significantly harder to solve than the integer factorization problem for the same key length. This allows ECC to achieve strong security with much smaller key sizes, making it ideal for resource-constrained IoT devices where memory, power, and processing are limited.

Exam trap

The SSCP exam often tests the misconception that larger key sizes always mean stronger security, leading candidates to pick RSA 2048-bit or Diffie-Hellman 2048-bit, while the trap is that ECC with much smaller key sizes (e.g., 256-bit) provides equivalent security with lower computational overhead, which is the exact requirement for IoT devices.

How to eliminate wrong answers

Option A is wrong because RSA with 2048-bit keys is the baseline for comparison, not a smaller key size alternative, and it requires significantly more computational resources than ECC for equivalent security. Option C is wrong because Diffie-Hellman with 2048-bit keys is a symmetric-key-agreement protocol that also uses large key sizes for security, not a smaller key size alternative, and it does not provide the same key-size efficiency as ECC. Option D is wrong because 3DES with 168-bit keys is a symmetric encryption algorithm, not an asymmetric algorithm, and it provides only about 112 bits of security, far less than RSA 2048-bit, while also being computationally heavy and deprecated in modern standards.

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Multi-Selecteasy

A security administrator is setting up a public key infrastructure (PKI) for internal use. Which two of the following components are essential for establishing a chain of trust from the root CA to end-entity certificates?

Select 2 answers

A.An intermediate (subordinate) CA certificate signed by the root CA

B.A certificate signing request (CSR)

C.A self-signed root CA certificate

D.An online certificate status protocol (OCSP) responder

E.A certificate revocation list (CRL)

AnswersA, C

Intermediate CAs issue end-entity certificates and are signed by the root CA, forming the chain.

Why this answer

The root CA must be self-signed (trust anchor), and intermediate CAs (subordinate) are used to issue end-entity certificates. CRLs and OCSP are revocation mechanisms, not trust chain components. CSR is for requesting certificates.

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MCQhard

A PKI administrator needs to check the revocation status of a digital certificate without requiring the client to download the entire CRL. Which method is designed for online, real-time certificate status checking?

A.OCSP

B.OCSP stapling

C.CRL

D.Certificate transparency

AnswerA

OCSP provides real-time status.

Why this answer

OCSP (Online Certificate Status Protocol) allows real-time checking of a certificate's revocation status without downloading the full CRL.

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MCQmedium

A company wants to implement a key management system. They need to generate cryptographic keys that are unpredictable. Which source of randomness should be used?

A.Hardware random number generator (HRNG)

B.Random numbers from a website

C.Linear congruential generator (LCG)

D.Pseudorandom number generator (PRNG) seeded with current timestamp

AnswerA

HRNGs provide high-quality entropy suitable for key generation.

Why this answer

A hardware random number generator (HRNG) is the correct choice because it derives randomness from physical processes (e.g., thermal noise, quantum effects) that are inherently unpredictable and non-deterministic. Cryptographic key generation requires true entropy to resist brute-force and prediction attacks, which software-based deterministic methods cannot guarantee.

Exam trap

ISC2 SSCP often tests the misconception that a PRNG seeded with a timestamp is sufficient for cryptography, but the trap is that timestamps are predictable or guessable, making the output deterministic and insecure for key generation.

How to eliminate wrong answers

Option B is wrong because random numbers from a website are sourced over an untrusted network and may be intercepted, reused, or generated by a pseudorandom algorithm, offering no verifiable entropy. Option C is wrong because a linear congruential generator (LCG) is a deterministic, predictable algorithm with a short period, making it unsuitable for cryptographic key generation. Option D is wrong because a pseudorandom number generator (PRNG) seeded with a current timestamp is deterministic; if the timestamp is guessed or observed, all outputs become predictable, violating the unpredictability requirement.

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MCQmedium

A security analyst is evaluating encryption modes for a new system that requires authenticated encryption to ensure both confidentiality and integrity of data in transit. Which AES mode should the analyst recommend?

A.ECB

B.CBC

C.CTR

D.GCM

AnswerD

GCM provides authenticated encryption.

Why this answer

GCM (Galois/Counter Mode) is the correct choice because it provides authenticated encryption, combining the confidentiality of CTR mode with integrity verification via a Galois field authentication tag. This makes it ideal for securing data in transit, as it ensures both privacy and tamper detection in a single, efficient operation.

Exam trap

The trap here is that candidates often confuse confidentiality-only modes (like CBC or CTR) with authenticated encryption, overlooking that GCM is the only option listed that natively provides both encryption and integrity in a single mode.

How to eliminate wrong answers

Option A is wrong because ECB (Electronic Codebook) mode encrypts each block independently, producing identical ciphertext for identical plaintext blocks, which leaks patterns and provides no integrity protection. Option B is wrong because CBC (Cipher Block Chaining) mode ensures confidentiality through chaining but does not inherently provide authentication or integrity; it requires a separate MAC (e.g., HMAC) for authenticated encryption. Option C is wrong because CTR (Counter) mode offers confidentiality by encrypting a counter value, but like CBC, it lacks built-in integrity verification and is vulnerable to bit-flipping attacks without an additional authentication mechanism.

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MCQeasy

Which of the following is a secure hash algorithm currently recommended by NIST?

A.SHA-1

B.RC4

C.MD5

D.SHA-256

AnswerD

SHA-256 is a current standard and is considered secure.

Why this answer

SHA-256 is a member of the SHA-2 family of secure hash algorithms and is currently recommended by NIST for cryptographic use. It produces a 256-bit (32-byte) hash value and is widely deployed in protocols such as TLS, SSH, and IPsec, as well as in digital signatures and certificate validation.

Exam trap

ISC2 SSCP exams often test the distinction between hash algorithms and encryption ciphers, so candidates may mistakenly select RC4 because it is a well-known cryptographic algorithm, but it is not a hash function at all.

How to eliminate wrong answers

Option A is wrong because SHA-1 is no longer considered secure by NIST due to demonstrated collision attacks (e.g., the SHAttered attack in 2017) and is deprecated for most cryptographic applications. Option B is wrong because RC4 is a stream cipher, not a hash algorithm, and it is also deprecated due to severe biases in its output. Option C is wrong because MD5 is a broken hash algorithm with practical collision attacks (e.g., used in the Flame malware) and is explicitly not recommended by NIST for any security purpose.

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Multi-Selecthard

A security engineer is designing a key management system for a large enterprise. Which two of the following practices are essential for securing cryptographic keys throughout their lifecycle?

Select 2 answers

A.Store keys in dedicated hardware security modules (HSMs).

B.Use the same key for encryption, digital signatures, and key exchange.

C.Email keys to authorized users for convenience.

D.Store keys in the same database as encrypted data.

E.Rotate keys regularly and upon compromise.

AnswersA, E

HSMs provide tamper-resistant storage and protect keys from unauthorized access.

Why this answer

Key storage in hardware security modules (HSMs) and regular key rotation are critical for key security. Storing keys with the data and emailing them violate security best practices. Using a single key for all purposes reduces security.

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Multi-Selectmedium

A company is upgrading its legacy systems to use modern cryptographic standards. Which two of the following algorithms should be avoided due to known weaknesses or deprecation?

Select 2 answers

A.SHA-256 for hashing

B.MD5 for hashing

C.AES-256 for encryption

D.ECDH for key exchange

E.3DES for encryption

AnswersB, E

MD5 is cryptographically broken; collision attacks are feasible.

Why this answer

MD5 and 3DES are considered weak: MD5 has collision vulnerabilities, and 3DES is deprecated due to small block size and performance issues. SHA-256, AES-256, and ECDH are modern and secure.

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MCQeasy

Which of the following is a secure protocol for remote administration of a server, replacing insecure protocols like Telnet?

A.FTP

B.SSH

C.HTTP

D.Telnet

AnswerB

SSH encrypts all traffic, making it secure for remote administration.

Why this answer

SSH (Secure Shell) is the correct answer because it provides encrypted remote administration capabilities, replacing insecure protocols like Telnet that transmit data in plaintext. SSH uses public-key cryptography for authentication and symmetric encryption (e.g., AES, ChaCha20) for session confidentiality, protecting against eavesdropping and man-in-the-middle attacks.

Exam trap

The trap here is that candidates may confuse Telnet with SSH or think that FTP or HTTP can be used for remote administration, but the question specifically asks for a secure replacement for Telnet, which is SSH.

How to eliminate wrong answers

Option A (FTP) is wrong because it is a file transfer protocol, not a remote administration protocol, and it transmits credentials and data in plaintext unless secured with FTPS or SFTP. Option C (HTTP) is wrong because it is a web protocol used for transferring hypertext, not for remote server administration, and it lacks encryption by default (HTTPS is the secure variant). Option D (Telnet) is wrong because it is the very insecure protocol that SSH replaces, sending all data including passwords in cleartext over TCP port 23.

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Multi-Selecteasy

Which TWO of the following are considered secure cryptographic hash functions as of current standards? (Select TWO.)

Select 2 answers

A.SHA-3

B.RC4

C.SHA-1

D.MD5

E.SHA-256

AnswersA, E

SHA-3 is the latest standard.

Why this answer

SHA-256 and SHA-3 are currently secure. MD5 and SHA-1 are broken or deprecated.

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Multi-Selecthard

A company is selecting a cryptographic algorithm for digital signatures. Which THREE of the following algorithms can be used for digital signatures? (Select THREE.)

Select 3 answers

A.SHA-256

B.DSA

C.AES

D.RSA

E.ECDSA

AnswersB, D, E

DSA is a digital signature algorithm.

Why this answer

RSA, ECDSA, and DSA are all capable of digital signatures. AES is symmetric and not for signatures; SHA-256 is a hash function.

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MCQhard

A security administrator is configuring a web server to use TLS. They want to optimize performance while maintaining strong security. Which cipher suite should they prioritize?

A.TLS_DHE_RSA_WITH_AES_128_CBC_SHA

B.TLS_RSA_WITH_AES_128_CBC_SHA256

C.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256

D.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384

AnswerD

This suite offers forward secrecy, strong authentication with ECDSA, and efficient authenticated encryption.

Why this answer

TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 uses Elliptic Curve Diffie-Hellman Ephemeral (ECDHE) for perfect forward secrecy, ECDSA for efficient authentication, AES-256 in GCM mode for authenticated encryption, and SHA-384 for integrity. This combination provides the strongest security with modern, optimized algorithms, making it the best choice for performance and security on a TLS web server.

Exam trap

The trap here is that candidates often choose option C (ECDHE_RSA) because it uses ECDHE and GCM, but they overlook that ECDSA with AES-256 and SHA-384 provides stronger security and better performance than RSA-based authentication, especially in modern TLS configurations.

How to eliminate wrong answers

Option A is wrong because TLS_DHE_RSA_WITH_AES_128_CBC_SHA uses DHE (which is slower than ECDHE due to larger key sizes) and CBC mode (which is vulnerable to padding oracle attacks like POODLE) with SHA-1 (deprecated due to collision attacks). Option B is wrong because TLS_RSA_WITH_AES_128_CBC_SHA256 uses RSA key exchange (no perfect forward secrecy, as the private key can decrypt all past sessions if compromised) and CBC mode (still susceptible to timing attacks). Option C is wrong because TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 uses RSA for authentication (larger keys, slower than ECDSA) and AES-128 (weaker than AES-256 for long-term security), while the question asks to prioritize the strongest combination; ECDSA with AES-256 and SHA-384 is superior.

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MCQhard

A security professional is designing a key management system and needs to ensure that keys are generated using a truly random source. Which of the following is the most appropriate method for generating cryptographic keys?

A.Hardware random number generator

B.Cryptographically secure PRNG seeded with a static password

C.Pseudorandom number generator (PRNG) seeded with current timestamp

D.User-memorized passphrase

AnswerA

Hardware RNG provides true randomness.

Why this answer

Hardware random number generators (HRNGs) provide true randomness, while CSPRNGs are deterministic. For key generation, a hardware RNG is best.

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Multi-Selectmedium

An organization is implementing a digital signature solution to ensure non-repudiation and integrity of documents. Which three of the following are true regarding digital signatures?

Select 3 answers

A.The receiver uses the sender's private key to verify the signature.

B.The receiver verifies the signature using the sender's public key.

C.The sender encrypts the entire document with their public key to create a signature.

D.Digital signatures provide non-repudiation because the private key is kept secret by the sender.

E.The sender signs the message hash with their private key.

AnswersB, D, E

Verification involves decrypting the signature with the sender's public key and comparing the hash.

Why this answer

Digital signatures involve signing the hash of the message with the sender's private key. They provide non-repudiation because only the sender has the private key. Verification uses the sender's public key.

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MCQmedium

An organization uses a PKI with a root CA that issues certificates to intermediate CAs, which then issue end-entity certificates. A client receives an end-entity certificate signed by an intermediate CA. During validation, which certificates are required to build the chain of trust?

A.Only the root CA certificate

B.End-entity certificate, intermediate CA certificate, and root CA certificate

C.Only the end-entity certificate and the root CA certificate

D.Only the end-entity certificate and the intermediate CA certificate

AnswerB

All three are required to validate the chain from end-entity to the trusted root.

Why this answer

In a PKI hierarchy, the chain of trust requires each certificate in the path to be validated up to a trusted root. The client must have the end-entity certificate, the intermediate CA certificate (to verify the end-entity's signature), and the root CA certificate (to verify the intermediate CA's signature). Without the intermediate CA certificate, the client cannot cryptographically link the end-entity to the root, breaking the chain.

Exam trap

The trap here is that candidates often assume the root CA directly signs all certificates, forgetting that intermediate CAs are used in practice, so they incorrectly select Option C or D, missing the need for the full chain.

How to eliminate wrong answers

Option A is wrong because the root CA certificate alone cannot verify the end-entity certificate's signature, which was issued by the intermediate CA, not the root. Option C is wrong because omitting the intermediate CA certificate leaves a gap in the chain; the client cannot validate the intermediate CA's signature on the end-entity certificate. Option D is wrong because without the root CA certificate, the client cannot verify the intermediate CA certificate's signature, so the chain of trust cannot be anchored to a trusted root.

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MCQeasy

A security analyst is recommending a symmetric encryption algorithm for a new application that requires both confidentiality and authentication. Which algorithm and mode combination should they select?

A.3DES-CBC

B.AES-ECB

C.RC4

D.AES-GCM

AnswerD

GCM mode combines encryption and authentication, making it ideal for this requirement.

Why this answer

AES-GCM (Galois/Counter Mode) is a symmetric encryption algorithm that provides both confidentiality and authentication in a single, efficient operation. It combines AES encryption in counter mode with a Galois field-based message authentication code (GMAC), making it ideal for applications requiring both security properties.

Exam trap

The trap here is that candidates often confuse CBC mode with providing authentication (since it uses an IV), but CBC only offers confidentiality; GCM is the correct choice for combined confidentiality and authentication in symmetric encryption.

How to eliminate wrong answers

Option A is wrong because 3DES-CBC provides only confidentiality, not authentication; CBC mode requires a separate MAC (e.g., HMAC) to ensure integrity and authenticity, and 3DES is deprecated due to its 64-bit block size and slow performance. Option B is wrong because AES-ECB is deterministic and does not provide authentication; it encrypts identical plaintext blocks into identical ciphertext blocks, leaking patterns and lacking any integrity check. Option C is wrong because RC4 is a stream cipher that provides only confidentiality, not authentication, and is considered broken due to biases in its output (e.g., RC4 biases in TLS), making it unsuitable for secure applications.

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