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- In a key-agreement protocol, two parties derive a shared secret over an insecure channel. Which of these is a classical example?
a. RSA encryption
b. Diffie–Hellman
c. AES block cipher
d. MD5 hash
Answer: b. Diffie–Hellman (it is a widely used key exchange method) (Wikipedia) - Which property is primarily provided by a cryptographic digital signature?
a. Confidentiality
b. Non-repudiation
c. Confidentiality + Integrity
d. Availability
Answer: b. Non-repudiation (digital signatures bind the signer to the message) - In the TLS protocol, which layer is responsible for negotiating cipher suites and keys?
a. Application layer
b. Record layer
c. Handshake layer
d. Transport layer
Answer: c. Handshake layer - In the Needham–Schroeder public-key protocol, one of the main vulnerabilities arises from:
a. Replay attacks
b. Key exhaustion
c. Side-channel leaks
d. Poor randomness
Answer: a. Replay attacks - In the Otway–Rees protocol, the trusted third party (TTP) is used to:
a. Distribute time stamps
b. Relay messages and authenticate identities
c. Encrypt symmetric keys using symmetric primitives
d. Manage user certificates
Answer: b. Relay messages and authenticate identities - Which protocol extension adds forward secrecy to TLS by using ephemeral ephemeral keys (ECDHE)?
a. TLS_RSA
b. TLS_DH
c. TLS_ECDHE
d. TLS_NULL
Answer: c. TLS_ECDHE - In IPSec, the AH (Authentication Header) protocol provides:
a. Confidentiality
b. Integrity and authentication
c. Only encryption
d. Only compression
Answer: b. Integrity and authentication (Quizlet) - Which of these is not an authenticated key exchange (AKE) property?
a. Key confirmation
b. Impersonation resistance
c. Confidentiality
d. Key renewal
Answer: c. Confidentiality (confidentiality is usually separate; AKE is about authentication and key agreement) - Which cryptographic primitive is used inside the Kerberos protocol for session key encryption?
a. Asymmetric RSA
b. Diffie–Hellman
c. Symmetric block cipher (e.g. AES)
d. Hash function alone
Answer: c. Symmetric block cipher (Kerberos uses symmetric encryption for tickets) - In the TLS 1.3 handshake, the Finished message is protected under which key?
a. The client’s public key
b. Early data key
c. Handshake traffic key
d. Application traffic key
Answer: c. Handshake traffic key - Which protocol uses a challenge–response to verify freshness and avoid replay attacks?
a. SSL
b. CHAP
c. FTP
d. SMTP
Answer: b. CHAP (uses challenge–response) - What is the role of a nonce in cryptographic protocols?
a. To enable forward secrecy
b. To act as a long-term key
c. To ensure freshness
d. To verify identity
Answer: c. To ensure freshness - The Fiat–Shamir heuristic transforms an interactive identification protocol into:
a. A symmetric key distribution scheme
b. A block cipher
c. A digital signature scheme
d. A public key encryption scheme
Answer: c. A digital signature scheme (Wikipedia) - In the Kerberos protocol, the Ticket Granting Ticket (TGT) is encrypted using which key?
a. The user’s password-derived key
b. The KDC’s long-term key
c. The client’s public key
d. A one-time pad
Answer: b. The KDC’s long-term key - In the context of cryptographic protocols, forward secrecy ensures that:
a. If current keys are compromised, past session keys remain safe
b. Future keys are predictable
c. Keys never expire
d. Only symmetric keys are used
Answer: a. If current keys are compromised, past session keys remain safe - Which of the following protocols was shown vulnerable to the “Logjam” attack?
a. TLS using DHE with weak primes
b. TLS using RSA only
c. IPSec ESP with 3DES
d. SSH using public key
Answer: a. TLS using DHE with weak primes - In an authenticated encryption (AE) scheme, the typical goal is to achieve:
a. Confidentiality only
b. Integrity only
c. Confidentiality + integrity
d. Availability
Answer: c. Confidentiality + integrity - The Station-to-Station (STS) protocol augments Diffie–Hellman with:
a. Hash functions only
b. Public key signatures to provide authentication
c. Symmetric key fallback
d. No additional features
Answer: b. Public key signatures to provide authentication - In the TLS protocol stack, the Record protocol is responsible for:
a. Key exchange
b. Session resumption
c. Fragmentation, compression, and encryption of application data
d. Certificate verification
Answer: c. Fragmentation, compression, and encryption of application data - Which version of TLS removed support for the RSA key-exchange mode to favor forward secrecy?
a. TLS 1.0
b. TLS 1.1
c. TLS 1.2
d. TLS 1.3
Answer: d. TLS 1.3 - The ISO/IEC 11770-3 standard is concerned with:
a. Block cipher modes
b. Key management using public key techniques
c. Hash function standards
d. Quantum cryptography
Answer: b. Key management using public key techniques - Which formal logic is often used to analyze security protocols (authentication, secrecy, etc.)?
a. Propositional logic
b. BAN logic (Burrows–Abadi–Needham)
c. Predicate logic only
d. Fuzzy logic
Answer: b. BAN logic - The Needham–Schroeder symmetric key protocol was improved by:
a. Eliminating nonces
b. Using only public key
c. The addition of timestamps to prevent replay
d. Replacing symmetric encryption with hash functions
Answer: c. The addition of timestamps to prevent replay - In EAP (Extensible Authentication Protocol) used in WPA2-Enterprise, the outer protocol is often:
a. TLS (in EAP-TLS)
b. SSH
c. Kerberos
d. SSL v2
Answer: a. TLS (in EAP-TLS) - In the ISO standard X.509, a certificate is signed by:
a. The subject itself
b. A certificate authority (CA)
c. A random third party
d. No signature
Answer: b. A certificate authority (CA) - The SRP (Secure Remote Password) protocol is a zero-knowledge password protocol that resists:
a. Offline dictionary attacks
b. Man-in-the-middle on public keys
c. Replay only
d. Only denial-of-service
Answer: a. Offline dictionary attacks - The AKE (Authenticated Key Exchange) security goal “key indistinguishability” implies that:
a. The key is always known
b. The key is indistinguishable from random by adversary
c. The key is public
d. The key is fixed
Answer: b. The key is indistinguishable from random by adversary - Which of the following is not a part of the ISO OSI model under which TLS-like protocols generally map?
a. Presentation
b. Session
c. Application
d. Physical
Answer: d. Physical - In IPsec, the ESP (Encapsulating Security Payload) protocol provides:
a. Only integrity
b. Only authentication
c. Confidentiality, integrity, and optional authentication
d. Only compression
Answer: c. Confidentiality, integrity, and optional authentication - In the TLS ClientHello message, the supported_versions extension is used for:
a. Negotiating the highest version both sides support
b. Sending the client certificate
c. Requesting session tickets
d. Encrypting the handshake immediately
Answer: a. Negotiating the highest version both sides support - The Widely used principle in protocol design that states “no security by obscurity, assume attacker knows protocol” is often tied to:
a. Kerckhoffs’s principle
b. Shannon’s maxim
c. Moore’s law
d. Heisenberg principle
Answer: a. Kerckhoffs’s principle - Which protocol is used to distribute public keys and support certificate revocation?
a. Diffie–Hellman
b. Kerberos
c. Online Certificate Status Protocol (OCSP)
d. IPsec AH
Answer: c. OCSP - The SSLv2 protocol was deprecated because:
a. It used weak MAC integrity checks
b. It lacked protection for handshake integrity
c. It was vulnerable to rollback attacks
d. All of the above
Answer: d. All of the above - The HMAC construction is typically used inside protocols for:
a. Encrypting the message
b. Hashing only
c. Message authentication codes
d. Key exchange
Answer: c. Message authentication codes - In authenticated encryption with associated data (AEAD), what is “associated data”?
a. Data that is encrypted but not authenticated
b. Data that is authenticated but not encrypted
c. Data both encrypted and authenticated
d. Data neither encrypted nor authenticated
Answer: b. Data that is authenticated but not encrypted - The TLS False Start optimization allows:
a. The client to send application data before handshake is done
b. The server to skip certificate verification
c. No encryption in early data
d. Session tickets only
Answer: a. The client to send application data before handshake is done - In a formal model, a Dolev–Yao adversary is characterized by:
a. Only passive eavesdropping
b. Full control over network (intercept, modify, inject)
c. Ability only to break cryptographic primitives
d. Limited to traffic analysis only
Answer: b. Full control over network (intercept, modify, inject) - The Kerberos protocol uses which type of trust model?
a. Hierarchical trust with KDC
b. Web-of-trust
c. Peer-to-peer trust
d. Blockchain-based trust
Answer: a. Hierarchical trust with KDC - The TLS renegotiation vulnerability (CVE-2009-3555) was remedied by:
a. Disabling renegotiation entirely
b. Introducing a renegotiation_info extension
c. Enforcing only TLS 1.3
d. Removing client authentication
Answer: b. Introducing a renegotiation_info extension - In the PAKE (Password Authenticated Key Exchange) protocols, the goal is:
a. To send password in clear text
b. To derive a key using password without revealing it
c. To use RSA inside password exchange
d. To require third-party server
Answer: b. To derive a key using password without revealing it - The IKEv2 protocol in IPsec is used to:
a. Only encrypt data
b. Negotiate SAs (Security Associations) and keys
c. Replace TCP
d. Compress packets
Answer: b. Negotiate SAs and keys - The “random oracle model” is often used to:
a. Prove security of protocols assuming ideal hash functions
b. Build symmetric ciphers
c. Design networks
d. Replace block ciphers
Answer: a. Prove security of protocols assuming ideal hash functions - In the TLS handshake, a Finished message includes a hash over:
a. The client random only
b. The server random only
c. The entire handshake transcript
d. The application data
Answer: c. The entire handshake transcript - The SIGMA family of protocols (used in IKE) stands for:
a. Simple Internet Gateway for Management and Authentication
b. SIGn-and-MAc
c. Secure Internet Group Management Architecture
d. Signature + symmetric MAC
Answer: b. SIGn-and-MAc - The Secure Shell (SSH) protocol provides secure remote login, and uses which key exchange by default?
a. RSA only
b. Diffie–Hellman group exchange
c. AES
d. MD5
Answer: b. Diffie–Hellman group exchange - In the TLS session resumption via PSK (pre-shared key), the protocol ensures:
a. No replay protection
b. Forward secrecy always
c. Faster handshake with fewer round trips
d. Public key is re-sent
Answer: c. Faster handshake with fewer round trips - In a formal proof, a protocol is said to satisfy the “secrecy property” if:
a. The adversary never learns the key
b. The adversary can break one instance
c. The adversary knows everything
d. The adversary bypasses authentication
Answer: a. The adversary never learns the key - Which cryptographic protocol is based on quantum physics rather than computational hardness?
a. RSA
b. AES
c. Quantum key distribution (QKD)
d. ECC
Answer: c. Quantum key distribution (QKD) (Wikipedia) - In the TLS 1.3 zero-RTT mode, a risk is:
a. Loss of confidentiality
b. Replay attack of early data
c. No encryption at all
d. Server not authenticated
Answer: b. Replay attack of early data - The Sakai–Kasahara scheme is an example of:
a. Symmetric encryption
b. Identity-based encryption (IBE)
c. Public-key infrastructure (PKI) without identities
d. Hash-based signature
Answer: b. Identity-based encryption (IBE) (Wikipedia)
