CompTIA Security+ — All Questions

Which type of encryption uses the same key to encrypt and decrypt data?

• a.Asymmetric
• b.Hashing
• c.Symmetric✓
• d.Steganographic

Symmetric encryption uses a single shared secret key for both encryption and decryption, such as AES. It is fast and suited to bulk data. The main challenge is securely distributing the shared key.

Which cryptographic method uses a public and private key pair?

• a.Asymmetric encryption✓
• b.Salting
• c.Hashing
• d.Symmetric encryption

Asymmetric encryption uses a mathematically linked key pair: a public key to encrypt and a private key to decrypt, or the reverse for signatures. It solves the key distribution problem of symmetric systems. RSA and elliptic curve are common examples.

Which one-way function produces a fixed-length value that cannot be reversed to the original input?

• a.Steganography
• b.Symmetric cipher
• c.Hashing✓
• d.Tokenization

Hashing transforms input into a fixed-length digest that cannot be feasibly reversed. It verifies integrity because any change to the input changes the hash. SHA-256 is a widely used secure hashing algorithm.

Adding a unique random value to each password before hashing to defeat precomputed attacks is called:

• a.Salting✓
• b.Peppering
• c.Stretching
• d.Encoding

Salting prepends or appends a unique random value to each password before hashing. This ensures identical passwords produce different hashes and defeats rainbow tables. Each salt must be unique and stored alongside the hash.

Which entity in a PKI issues and signs digital certificates?

• a.Key escrow agent
• b.Certificate authority✓
• c.Registration authority
• d.Certificate holder

A certificate authority (CA) issues, signs, and vouches for digital certificates, binding a public key to an identity. Trust in the CA underpins the entire PKI. A compromised CA can undermine trust for all certificates it issued.

Which mechanism lets a client quickly check whether a single certificate has been revoked?

• a.Certificate pinning
• b.Key stretching
• c.Online Certificate Status Protocol✓
• d.Certificate signing request

The Online Certificate Status Protocol (OCSP) queries a responder in real time to check a certificate's revocation status. It is faster and more current than downloading a full certificate revocation list. OCSP stapling improves performance and privacy.

What does a digital signature primarily provide?

• a.Integrity and non-repudiation✓
• b.Availability
• c.Faster encryption
• d.Confidentiality only

A digital signature proves the message came from the holder of the private key and was not altered, giving integrity, authentication, and non-repudiation. It does not by itself keep the content secret. It is created by encrypting a hash with the signer's private key.

Which authentication factor category does a fingerprint belong to?

• a.Something you are✓
• b.Something you know
• c.Something you have
• d.Somewhere you are

A fingerprint is a biometric, which is the 'something you are' factor based on physical characteristics. Combining it with a different factor, such as a password, creates multifactor authentication. Biometrics resist sharing but raise privacy and revocation concerns.

Requiring a password plus a one-time code from a phone app is an example of:

• a.Role-based access
• b.Federation
• c.Multifactor authentication✓
• d.Single sign-on

Multifactor authentication combines two or more independent factor categories, here something you know and something you have. This greatly reduces the risk from a stolen password alone. An attacker would need to defeat both factors.

Which access control model grants permissions based on a user's assigned job function?

• a.Rule-based access control
• b.Mandatory access control
• c.Discretionary access control
• d.Role-based access control✓

Role-based access control (RBAC) assigns permissions to roles, and users inherit access by being placed in a role. It simplifies administration and enforces consistency. Changing a role updates access for everyone assigned to it.

Which model uses security labels and clearances, common in government, where the system enforces access centrally?

• a.Discretionary access control
• b.Attribute-based access control
• c.Mandatory access control✓
• d.Role-based access control

Mandatory access control (MAC) enforces access based on classification labels and clearances set by a central authority. Users cannot change permissions on resources they own. It is used where strict, non-discretionary control is required.

Which secure protocol replaces Telnet for encrypted remote command-line access?

• a.HTTP
• b.SNMPv1
• c.FTP
• d.SSH✓

Secure Shell (SSH) provides encrypted remote administration, replacing the plaintext Telnet protocol. It protects credentials and session data in transit. SSH also underpins secure file transfer and tunneling.

Which protocol secures web traffic by encrypting HTTP with TLS?

• a.SMTP
• b.LDAP
• c.SFTP
• d.HTTPS✓

HTTPS layers HTTP over TLS to encrypt web traffic, protecting confidentiality and integrity between browser and server. It also authenticates the server through its certificate. Modern sites should use TLS 1.2 or 1.3 with strong ciphers.

Which protocol provides secure file transfer by running over an SSH connection?

• a.TFTP
• b.FTPS
• c.SFTP✓
• d.HTTP

SFTP transfers files over an SSH channel, encrypting both credentials and data. It differs from FTPS, which is FTP secured with TLS. SFTP uses a single connection, simplifying firewall configuration.

Which technology creates an encrypted tunnel for remote users to access a private network over the internet?

• a.DMZ
• b.NAT
• c.VPN✓
• d.Proxy

A virtual private network (VPN) establishes an encrypted tunnel over an untrusted network, protecting traffic between the remote user and the corporate network. It preserves confidentiality and integrity in transit. IPsec and TLS are common VPN foundations.

Which single sign-on standard is widely used to exchange authentication data between identity providers and web applications?

• a.TACACS+
• b.SAML✓
• c.RADIUS
• d.Kerberos

Security Assertion Markup Language (SAML) exchanges authentication and authorization assertions between an identity provider and service providers, enabling web single sign-on. The identity provider vouches for the user so each application does not manage passwords. It is common in enterprise federation.

Replacing sensitive data such as a credit card number with a non-sensitive substitute value is called:

• a.Tokenization✓
• b.Hashing
• c.Salting
• d.Compression

Tokenization swaps sensitive data for a meaningless token, keeping the real value in a secure vault. The token has no exploitable value if stolen. It is widely used to reduce the scope of payment card data handling.

A dedicated hardware device that securely generates and stores cryptographic keys is a:

• a.Proximity token
• b.TPM
• c.Smart card
• d.Hardware security module✓

A hardware security module (HSM) is a tamper-resistant device that generates, stores, and manages cryptographic keys and performs crypto operations. It keeps keys isolated from general-purpose systems. HSMs are common in PKI and high-assurance environments.

Which chip on a motherboard stores keys and supports features like full-disk encryption and secure boot?

• a.Smart card
• b.CPU cache
• c.HSM
• d.Trusted Platform Module✓

The Trusted Platform Module (TPM) is a chip integrated into a device that securely stores keys and measurements for boot integrity and disk encryption. It binds encryption to specific hardware. It underpins features like BitLocker and secure boot.

Which property ensures a sender cannot later deny having sent a signed message?

• a.Availability
• b.Non-repudiation✓
• c.Anonymity
• d.Confidentiality

Non-repudiation prevents a party from convincingly denying an action, such as sending a digitally signed message. It relies on the private key being unique to the signer. Digital signatures and reliable logs provide non-repudiation.

A bank requires customers to enter a password and then approve a push notification on their enrolled phone before accessing their account. Which authentication factors are being combined?

• a.Two separate instances of something you know, which does not truly raise assurance
• b.Something you know and something you have✓
• c.Something you are and somewhere you are, tied to a physical biometric location
• d.Something you have and something you do, based on continuous behavioral analysis

The password is knowledge (something you know) and the enrolled phone is possession (something you have), so two distinct factor categories are combined. Genuine multifactor authentication requires categories that fail independently, so stealing one does not defeat the other. Two passwords would still be a single category and add little assurance.

An organization deploys single sign-on so employees authenticate once to reach many applications. What is the primary security trade-off administrators must plan for?

• a.A compromised SSO credential can unlock every connected application at once✓
• b.Encryption of network traffic between the applications is automatically disabled by design
• c.Users are forced to memorize a separate, complex password for every individual application they use
• d.Applications can no longer share any authentication information between one another

SSO concentrates risk because one authentication grants access to many systems, so a stolen SSO credential becomes a master key. That is why SSO should be paired with strong MFA and session controls. The convenience of one login is exactly what raises the stakes if it is compromised.

A user logs into a partner's cloud application using their own company credentials, and the company's identity system vouches for them. In this federated setup, what role does the company's identity system play?

• a.Certificate authority that signs the TLS certificate presented by the application
• b.Service provider, which hosts the partner application and stores its user data
• c.Relying party that consumes the assertion and makes the final resource decision
• d.Identity provider that authenticates the user and issues assertions✓

In federation the identity provider (IdP) authenticates the user and issues a signed assertion, while the partner acts as the service provider or relying party that trusts it. This lets users access external apps without those apps ever handling company passwords. Distinguishing the IdP from the SP is central to understanding SAML and OIDC flows.

A photo-printing website asks to access a user's cloud photo library without ever seeing the user's cloud password, using a delegated access token. Which framework is being used?

• a.OAuth 2.0✓
• b.Kerberos
• c.RADIUS
• d.SAML browser single sign-on

OAuth 2.0 is an authorization framework that issues scoped access tokens so one service can act on a user's behalf without receiving their password. It delegates access, not identity, which is why scopes limit what the token can do. Limiting scope and token lifetime is key to using it safely.

A developer needs not just delegated access but also verified identity information about the user, returned in a signed ID token. Which protocol layered on OAuth 2.0 provides this?

• a.802.1X
• b.LDAP
• c.TACACS+, which separates authentication, authorization, and accounting for device admin
• d.OpenID Connect✓

OpenID Connect adds an identity layer on top of OAuth 2.0, returning a signed ID token that proves who the user is. OAuth alone handles authorization, so OIDC is what supplies authenticated identity. This distinction is why OIDC is used for modern web and mobile sign-in.

In a Windows domain, a workstation presents a time-stamped ticket to reach a file server without re-entering a password. Why does Kerberos rely on tightly synchronized clocks across the domain?

• a.Because tickets are stored permanently and never expire once they are issued to a host
• b.Because time stamps limit ticket validity and help prevent replay attacks✓
• c.Because the key distribution center encrypts all file contents using the workstation clock
• d.Because domain controllers bill each user for the exact number of seconds of access used

Kerberos tickets carry time stamps and short lifetimes, so synchronized clocks let servers reject stale or replayed tickets. If clocks drift too far apart, valid tickets are refused and stale ones might be accepted. This is why time synchronization is a hard requirement in Kerberos realms.

An administrator notices directory queries and bind credentials are traveling in cleartext over port 389. Which change encrypts this directory traffic?

• a.Disable anonymous binds but keep the existing plaintext connection on port 389
• b.Move the directory server into the screened subnet that faces the public internet
• c.Use LDAPS, wrapping LDAP in TLS on port 636✓
• d.Switch the directory to broadcast its queries over UDP so that lookups complete faster

LDAPS encapsulates LDAP inside TLS, typically on port 636, encrypting both queries and bind credentials in transit. Cleartext LDAP exposes directory passwords to any on-path attacker. Encrypting the channel, not just restricting binds, is what protects the credentials.

A network team wants centralized administrator login to routers with the ability to authorize individual commands and log each one separately. Which protocol best fits because it separates authentication, authorization, and accounting?

• a.TACACS+✓
• b.SAML
• c.RADIUS
• d.Kerberos

TACACS+ separates authentication, authorization, and accounting into independent functions, enabling per-command authorization and detailed logging for device administration. RADIUS merges authentication and authorization, giving less granular command control. This separation is why TACACS+ is favored for network device admin.

To reduce standing administrative rights, a company grants elevated access only for a short approved window and records the session. Which control is this?

• a.Mandatory access control, enforcing sensitivity labels assigned by a central authority
• b.Privileged access management with just-in-time elevation✓
• c.Discretionary access control, letting each resource owner set their own file permissions
• d.Single sign-on, which authenticates the user once for access to many applications

Privileged access management with just-in-time elevation removes always-on admin rights, granting them briefly on request and recording the activity. This shrinks the window an attacker can abuse stolen admin credentials. Time-boxing and session recording are what distinguish it from static privileged accounts.

A DevOps team stops hardcoding database passwords in scripts and instead retrieves them at runtime from a centralized secrets manager that rotates them automatically. What risk does this primarily reduce?

• a.The risk of exposed, static, long-lived credentials embedded directly in source code✓
• b.The risk that end users will choose weak passphrases for their own personal accounts
• c.The risk that TLS certificates will silently expire and break client connections later
• d.The risk of denial-of-service caused by too many simultaneous inbound connections

A secrets manager keeps credentials out of code and rotates them, so a leaked repository or old backup no longer hands attackers valid passwords. Hardcoded secrets are long-lived and hard to rotate once exposed. Centralized, rotating retrieval directly addresses that exposure.

An access system evaluates the user's department, the device's health, the time of day, and data sensitivity before allowing a request. Which access control model is described?

• a.Discretionary access control, where the owner of the resource decides access
• b.Attribute-based access control✓
• c.Rule-based access control
• d.Role-based access control

Attribute-based access control (ABAC) makes decisions from multiple attributes of the user, device, resource, and context, enabling fine-grained, dynamic policies. Role-based control keys only on job role and is less context-aware. Combining many attributes is the defining trait of ABAC.

A cloud platform blocks logins from unmanaged devices and requires MFA when a sign-in comes from an unusual country. What is this adaptive approach called?

• a.Implicit trust, which grants access automatically to anyone already inside the network
• b.Full-disk encryption, which protects data stored locally on the endpoint while at rest
• c.Conditional access based on risk and device posture✓
• d.Static access lists that never change regardless of context or the current risk signals

Conditional access evaluates signals such as device compliance, location, and risk to decide whether and how to grant access, stepping up authentication when risk rises. It embodies zero-trust thinking by never trusting a session on network location alone. Adapting requirements to context is its central idea.

A security team tuning a fingerprint reader wants the setting where the false acceptance rate equals the false rejection rate, used to compare device accuracy. What is this point called?

• a.Crossover error rate✓
• b.The annualized rate of occurrence
• c.The single loss expectancy
• d.Mean time to repair

The crossover error rate (CER) is where false acceptance and false rejection rates are equal, giving a single number to compare biometric accuracy. A lower CER means a more accurate sensor overall. It lets teams tune sensitivity while understanding the balance between wrongly admitting and wrongly rejecting users.

During an audit, several active accounts belong to employees who left the company months ago. Which identity lifecycle failure does this reveal?

• a.Failure to deprovision accounts promptly at offboarding✓
• b.Improper encryption of the directory database in which the user accounts are stored
• c.Excessive multifactor prompts that cause users to approve push requests carelessly
• d.Weak password complexity requirements enforced at the moment of initial account creation

Leftover active accounts show a breakdown in deprovisioning, the offboarding step that disables access when someone leaves. Orphaned accounts are prime targets because no one monitors them. Tying account deactivation to HR offboarding prevents this gap.

An engineer needs to encrypt large volumes of stored data quickly using a single shared key and selects AES. Why is a symmetric cipher like AES preferred here over an asymmetric one?

• a.Because asymmetric ciphers are technically unable to encrypt data of any size at all
• b.Because AES automatically distributes its own keys with no coordination required at all
• c.Because symmetric encryption uniquely provides non-repudiation of the original sender
• d.Because symmetric ciphers are much faster for bulk data encryption✓

Symmetric ciphers such as AES are far faster and less compute-intensive than asymmetric algorithms, making them ideal for encrypting large data volumes. Asymmetric crypto is slow and typically used only to exchange keys or sign. Speed on bulk data is the reason AES is chosen here.

A protocol encrypts a real-time voice stream one bit or byte at a time as it is generated, rather than in fixed 128-bit blocks. Which cipher type suits this continuous data best?

• a.An RSA cipher
• b.A stream cipher✓
• c.A one-way hash
• d.A block cipher in ECB mode

A stream cipher encrypts data continuously, bit or byte at a time, which fits real-time streams like voice where data arrives incrementally. Block ciphers work on fixed-size chunks and can add latency or padding. Matching the cipher to the data flow is the key idea here.

Two parties who have never met need to agree on a shared secret over an open network without ever transmitting the secret itself. Which mechanism enables this?

• a.A certificate revocation list
• b.A hash function
• c.Diffie-Hellman key exchange✓
• d.Symmetric AES encryption using a key shared beforehand

Diffie-Hellman lets two parties derive a shared secret over an untrusted channel without sending the secret, using public exchanges and private values. It solves the bootstrapping problem of symmetric keys. This is why it underpins secure session establishment in protocols like TLS.

A security architect wants assurance that if a server's long-term private key is later stolen, past recorded TLS sessions still cannot be decrypted. Which property, achieved with ephemeral keys, provides this?

• a.Perfect forward secrecy✓
• b.Non-repudiation
• c.Certificate pinning, which hardcodes an expected certificate into the client
• d.Key escrow

Perfect forward secrecy uses ephemeral, per-session keys that are discarded, so compromising the long-term key does not expose previously recorded sessions. Each session's secret is independent of the server's static key. This limits the blast radius of a future key theft.

A mobile device team wants strong asymmetric security with smaller keys and lower power use than RSA. Which algorithm family meets this need?

• a.SHA-3
• b.AES
• c.Elliptic curve cryptography✓
• d.RSA with 4096-bit keys, maximizing key length regardless of battery life

Elliptic curve cryptography achieves comparable security to RSA with much smaller keys, reducing computation, memory, and power draw. This efficiency suits constrained mobile and IoT devices. Smaller keys for equivalent strength are ECC's defining advantage.

To make stored password hashes far more expensive to crack, a developer chooses an algorithm deliberately designed to be slow and memory-hard, such as Argon2 or bcrypt. What is this technique called?

• a.Tokenization
• b.Certificate stapling
• c.Steganography
• d.Key stretching✓

Key stretching applies deliberately slow, resource-intensive functions like bcrypt, PBKDF2, or Argon2 so each password guess costs an attacker significant time. This blunts brute-force and dictionary attacks against stolen hashes. Intentional slowness is exactly the point of the technique.

An API includes a keyed hash with each message so the receiver can confirm both that the content is unchanged and that it came from a party sharing the secret key. What is this construct?

• a.A digital certificate
• b.An AES ciphertext block
• c.A hash
• d.An HMAC✓

A hash-based message authentication code (HMAC) combines a shared secret key with a hash, providing both integrity and authenticity. A plain hash detects change but not who produced it. Mixing in the secret key is what proves the message came from a key holder.

Before a certificate authority can issue a TLS certificate, an admin generates a request containing the server's public key and identifying details, signed by the matching private key. What is this request called?

• a.A certificate signing request✓
• b.A certificate revocation list, which lists certificates no longer trusted
• c.A key escrow deposit
• d.An OCSP response

A certificate signing request (CSR) packages the public key and identity information and is signed by the corresponding private key to prove key ownership. The CA validates it before issuing a signed certificate. The private key itself never leaves the requester, which is why only the CSR is sent.

To limit exposure of its most trusted key, an organization keeps its root CA offline and issues day-to-day certificates from a subordinate CA. What is the main security benefit?

• a.Clients can skip verifying the certificate chain entirely because the root is offline
• b.The intermediate CA removes the need to ever renew certificates before they expire
• c.The offline root key stays protected while the intermediate handles routine issuance✓
• d.Certificates no longer need to be validated against any revocation source by clients

Keeping the root CA offline protects the most critical key, while an intermediate CA does everyday signing. If an intermediate is compromised it can be revoked without destroying the entire trust hierarchy. This tiered design contains damage and preserves the root's integrity.

A high-traffic site wants clients to learn a certificate's revocation status without each client separately querying the CA, reducing latency and privacy leakage. Which approach fits?

• a.Pinning
• b.Distributing a full certificate revocation list to every browser hourly
• c.Disabling revocation checking
• d.OCSP stapling✓

OCSP stapling has the server periodically fetch a signed revocation status and attach it to the TLS handshake, so clients get proof without contacting the CA themselves. This cuts latency and stops the CA from seeing which clients visit. The server, not each client, does the checking.

A mobile banking app hardcodes the expected server certificate so that even a fraudulent but validly-signed certificate from another CA is rejected. This defense is called:

• a.Certificate pinning✓
• b.Key stretching
• c.Wildcard certification
• d.Cross-certification

Certificate pinning embeds the expected certificate or key in the app so it refuses any other certificate, even one a CA would normally trust. This blocks man-in-the-middle attacks using rogue but validly issued certificates. The trade-off is that pinned certificates must be updated before they change.

A company wants one certificate to secure store.example.com, mail.example.com, and any other host under example.com. Which certificate type covers all subdomains at one level?

• a.A code-signing certificate
• b.An extended validation certificate
• c.A root certificate
• d.A wildcard certificate✓

A wildcard certificate uses a name like *.example.com to secure any single-level subdomain, simplifying management. The convenience comes with risk, since one compromised private key affects every covered host. Understanding its scope and shared-key risk is the exam point.

An internal test server presents a certificate that no public CA vouches for, so browsers warn users. Why does a self-signed certificate trigger this warning?

• a.Because no trusted third party has verified the certificate's authenticity✓
• b.Because self-signed certificates are hardcoded to expire within twenty-four hours only
• c.Because self-signed certificates always use a weaker cipher than CA-issued certificates
• d.Because the private key is automatically published alongside the certificate's public key

A self-signed certificate is not vouched for by any CA in the browser's trust store, so the client cannot confirm the server's identity and warns the user. The encryption strength can be identical; the issue is missing third-party validation. Trust chaining, not cipher strength, is what is absent.

So encrypted data is not permanently lost when an employee leaves or forgets a passphrase, an organization stores a protected recovery copy of decryption keys with a trusted custodian. This practice is:

• a.Certificate pinning
• b.Perfect forward secrecy
• c.Salting
• d.Key escrow✓

Key escrow stores a recoverable copy of cryptographic keys with a trusted party so data can be recovered if the original key is lost. It supports business continuity but also creates a high-value target that must be tightly controlled. The recovery copy is the essence of escrow.

Anticipating that today's algorithms may weaken over time, an architect designs systems so cryptographic algorithms can be swapped with minimal disruption. This design goal is called:

• a.Steganography
• b.Cryptographic agility✓
• c.Homomorphic encryption
• d.Ephemeral keying

Cryptographic agility is designing systems so algorithms and key sizes can be replaced as standards evolve or weaknesses emerge. It matters because ciphers age and quantum computing threatens some today. Building in swap-ability avoids costly rip-and-replace later.

Before publishing a software update, a vendor signs the installer with its private key so users can verify the code's origin and that it was not modified. Which control is this?

• a.Code signing✓
• b.A certificate revocation list
• c.Hashing
• d.Full-disk encryption

Code signing attaches a digital signature to software so users can confirm the publisher and detect tampering before running it. A broken or missing signature signals modification or an untrusted source. This provides integrity and authenticity for distributed code.