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Lboro U - Telecommunications and Network Security > Vocabular / Concepts > Flashcards

Vocabular / Concepts Flashcards

1
Q

What is the purpose of the Diffie-Hellman protocol ? (2 points)

A
  • securely establish a shared secret key between two parties over an insecure communication channel
  • allows two parties to generate a common key without having to transmit the key itself, thus preventing interception by eavesdroppers
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2
Q

What is a digital signature ?

A

Message authentication + a measure to counter repudiation by the source

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3
Q

(Threat, Security Service, Comments, Mechanism)

Interception

A

Security Service : confidentiality
Comments : information is accessible only to authorized users
Mechanism : encryption

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4
Q

(Threat, Security Service, Comments, Mechanism)

Fabrication

A

Security Service : authentication
Comments : ensuring the identity of an entity / message not altered
Mechanism : authentication protocols

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5
Q

(Threat, Security Service, Comments, Mechanism)

Modification

A

Security Service : integrity
Comments : message is not tampered with
Mechanism : digital signature (e.g. RSA)

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6
Q

(Threat, Security Service, Comments, Mechanism)

Repudiation

A

Security Service : non-repudiation
Comments : the entity can’t deny sending/receiving a message
Mechanism : digital signature

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7
Q

(Threat, Security Service, Comments, Mechanism)

Unauthorized access

A

Security Service : access control
Comments : prevention of unauthorized use of resources
Mechanism : access control list, roles

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8
Q

(Threat, Security Service, Comments, Mechanism)

Interruption / Denial of service

A

Security Service : availability
Comments : services always available to authorized users
Mechanism : replication, more bandwidth, better hardware

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9
Q

Type of attack : Traffic analysis

A

Passive

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10
Q

Type of attack : Release of content

A

Passive

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11
Q

Type of attack : Replay

A

(intercept a transmission and repeat it, e.g. for ID theft)

Active

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12
Q

Type of attack : Modification of messages

A

Active

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13
Q

Type of attack : Denial of service

A

Active

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14
Q

Type of attack : Masquerade

A

(steal ID to pretend to be someone else)

Active

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15
Q

Outline a Man-in-middle attack for the Diffie-Hellman protocol

A
  1. Darth prepares for the attack by generating two random private keys Xd1 and Xd2 and then computing the corresponding public keys Yd1 and Yd2
  2. Alice transmits Ya to Bob
  3. Darth intercepts Ya and transmits Yd1 to Bob. Darth also calculates K2 = YAXd2 mod q
  4. Bob receives Yd1 and calculates K1 = Yd1Xb mod q
  5. Bob transmits Yb to Alice
  6. Darth intercepts Yb and transmits Yd2 to Alice. Darth calculates K1 = YbXd1 mod q
  7. Alice receives Yd2 and calculates K2 = Yd2Xa mod q
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16
Q

Sample Kerberos Exchange

A

C→AS : Hi, Jain would like to use the network today.
C←AS : Here is a day pass for Jain.
C→TGS : Jain would like to communicate with PrintServer. Attached is his day pass.
C←TGS : Here is the ticket for Jain to communicate with PrintServer. It includes a session key.
C→PrintServer : Hi, Jain wants to communicate with you, here is the ticket.
C←PrintServer : Perfect, let us use the session key that was in your ticket.

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17
Q

Where is SSL used ?

A

Widely in web, to secure HTTP

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18
Q

What are the layers of the SSL protocol ?

A

Two layers :
- SSL Record Protocol : secure, reliable channel
- upper layer = carrying : Handshake, Alert protocol, HTTP, Any other app.

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19
Q

What is a “session” in the SSL protocol ?

A
  • 1 client + 1 server
  • to define a set of cryptographic / security parameters shared among multiple connections
  • used to avoid the expensive negotiation of new security parameters for each connection
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20
Q

What is a “connection” in the SSL protocol ?

A
  • 2 peers (equal roles)
  • transient (temporary and short-lived)
  • 1 connection associated with 1 session
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21
Q

What are the 4 phases of the SSL Handshake Protocol ?

A
  1. Establishing security capabilities
  2. Server authentication and key exchange
  3. Client authentication and key exchange
  4. Finalizing the Handshake protocol
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22
Q

What is the goal of the SSL Alert Protocol ?

A

To warn the user that something went wrong, and directly provide insight on the problem with codes for alert messages (2 bytes)

23
Q

What is the layer of IPsec ?

A

Network layer

24
Q

What is contained in IPsec ?

A

AH: Authentication Header
ESP: Encapsulating Security Payload
IKE: Internet Key Exchange

25
Q

What is the use of AH + ESP in the scope of IPsec ?

A

Protection for IP traffic
AH → integrity + authentication
ESP → confidentiality

26
Q

What is the use of IKE in the scope of IPsec ?

A

To set up keys and algorithms for AH and ESP

27
Q

What are the two modes of IPsec ?

A

transport and tunnel

28
Q

What machines are connected in the transport mode for IPsec ?
What additional requirements are needed ?
What is a typical application ?

A

end-to-end security between two hosts (usually client ↔ gateway)
Requires IPsec support at each host (extra software)
PC to remote host

29
Q

What machines are connected in the tunnel mode for IPsec ?
What additional requirements are needed ?
What is a typical application ?

A

gateway ↔ gateway security
Internal traffic behind gateways not protected
Only requires IPsec support at gateways
VPN

30
Q

What does the SSL Handshake Protocol provides ?

A
  • confidentiality (shared secret key for encryption)
  • message integrity (using a MAC with the secret key)
31
Q

What are the attacks attempts to alter system resources or affect their operation ?

A

Active attacks

32
Q

What are the attack attempts to learn or make use of information from the system but does not affect system resources ?

A

Passive attacks

33
Q

What are the attack attempts that aim the disruption of access to or use of information or an information system ?

A

DDoS (Distributed Denial-of-Service)

34
Q

What are the attack attempts that aim to do unauthorized modification or destruction of information ?

A

Integrity attack

35
Q

Concerning Kerberos, when Bob receives a Ticket from Alice, how does he know it came from Alice?

A

It contains Alice’s name encrypted by the TGS-Bob secret key.

36
Q

Concerning Kerberos, when Alice receives a reply, how does she know it came from Bob and that it’s not a replay of an earlier message from Bob ?

A

It has a nonce (e.g., time stamp) encrypted with the session key.

37
Q

Concerning Kerberos, what does the Ticket contain that allows Alice and Bob to talk securely?

A

It contains the session key encrypted by the TGS-Bob secret key.

38
Q

What is a False Positive in the scope of intrusion detection systems ?

A

A legitimate action mistakenly flagged as malicious

39
Q

What is a False Negative in the scope of intrusion detection systems ?

A

A malicious action mistakenly unnoticed (or flagged as benign)

40
Q

Is public-key encryption more secure from cryptanalysis than symmetric encryption ?

A

No, they have different purposes so not comparable

41
Q

Is a one-time pad unbreakable ?

A

Yes if it is used correctly (only one use of the key, truly randomly generated key)

42
Q

Must it be relatively difficult to recognize and verify the digital signature ?

A

No, it must be easy to recognize for anyone who has access to the associated public key. Its security relying on the difficulty to forge a signature.

43
Q

Can an individual Security Association (SA) implement both the Authentication Header (AH) and the Encapsulating Security Payload (ESP) protocols ?

A

No, in IPsec, they are typically associated with either one of them, not both.

44
Q

Is a metamorphic virus a software that can be shipped unchanged to a heterogeneous collection of platforms and execute with identical semantics ?

A

No, it’s a virus that changes its shape and structure after each infection to avoid detection by an anti-virus software.

45
Q

What are two major vulnerabilities for the Diffie-Hellman protocol, and how to prevent them ?

A
  • Man-in-the-Middle attack → use digital signatures
  • perfect forward secrecy (if attacker manages to get A or B private key, he can decrypt the whole conversation) → use ephemeral keys
46
Q

Suppose A sends a message to B using RSA, but also needs to provide authentication. Explain how to use RSA to provide both confidentiality and authentication.

A

M → sign using A’s private key → encrypt using B’s public key → C

47
Q

Show how SSL reacts to the following three attacks: replay, password sniffing and IP spoofing.

A

Replay : Timestamp + sequence numbers
Password sniffing : end-to-end encryption
IP Spoofing : mutual authentication

48
Q

How does SSL deals with a man-in-the-middle attack ?

A

Authentication: Uses digital certificates to verify server identity

49
Q

How does SSL deals with a SYN flooding attack ?

A

SYN Cookies: Delays resource allocation until connection is verified.
Rate Limiting and Filtering: Limits incoming SYN request rates.
Intrusion Detection and Prevention Systems (IDPS)

50
Q

Can a honeypot machine be used by its legitimate owner to run standard services?

A

No because running standard services on honeypots exposes real data to potential compromise if the honeypot is attacked (which is its purpose)

51
Q

Is the purpose of compression of plaintext prior to encryption into ciphertext to reduce the amount of ciphertext which is vulnerable whilst in transit over the internet?

A
  • reduce data size (for transport and to increase encryption efficiency)
  • but it also enhances security (e.g. by removing patterns)
52
Q

2 advantages of Diffie-Hellman

A
  • no need for a prior shared exchange
  • obtain secret key without exchanging the key itself
53
Q

Explain how the man-in-the-middle attack is mitigated when Diffie-Hellman is used
in the TLS and IPSec, respectively.

A

TLS : Handshake → digital certificate → authentication

IPsec : mutual authentication

Lboro U - Telecommunications and Network Security (2 decks)

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