Industrial Network Security > Chapter 2 > Flashcards

Chapter 2 Flashcards

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1
Q

What is a network protocol?

A

A network protocol defines the format and order of messages exchanged between network entities and specifies which actions are taken when messages are sent or received.

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2
Q

What is unicast communication?

A

Unicast is point-to-point communication: one sender communicates with one receiver.

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3
Q

What is multicast communication?

A

Multicast is point-to-multipoint communication: one sender transmits to a defined group of receivers.

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4
Q

What is broadcast communication?

A

Broadcast is point-to-multipoint communication in which one sender transmits to many or all receivers, often without knowing each receiver individually.

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5
Q

What is simplex communication?

A

In simplex communication, data flows in only one direction.

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6
Q

What is half-duplex communication?

A

In half-duplex communication, both sides can send, but not at the same time.

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7
Q

What is full-duplex communication?

A

In full-duplex communication, both sides can send simultaneously.

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8
Q

Why are communication systems organized in layers?

A

They are organized in layers because networks are complex, and layering structures the many communication tasks by function and lets each layer provide services to the layer above it.

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9
Q

What does layer transparency mean?

A

Layer transparency means that the Protocol Data Unit of layer N+1 is treated as payload by layer N; the lower layer does not interpret the higher-layer content.

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10
Q

What is the relationship between an (N+1)-PDU and an N-SDU?

A

The (N+1)-PDU becomes the N-SDU, meaning the higher-layer protocol data unit is passed as service data to the next lower layer.

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11
Q

Name the seven layers of the OSI model in order.

A

Physical, Data Link, Network, Transport, Session, Presentation, Application.

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12
Q

Which OSI layers are transport-oriented?

A

Layers 1 to 4 are transport-oriented because they focus on end-to-end transfer of data without considering application semantics.

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13
Q

Which OSI layers are application-oriented?

A

Layers 5 to 7 are application-oriented because they deal with semantics, structuring, presentation, and application cooperation.

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14
Q

What is the task of the physical layer?

A

The physical layer provides an unreliable connection for transmitting unstructured bit sequences over the physical medium and standardizes the physical interface.

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15
Q

What is the task of the data link layer?

A

The data link layer provides reliable transfer between two hosts by framing bit streams and handling errors with mechanisms such as acknowledgements, time/sequence monitoring, retransmission, or reset.

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16
Q

What is the task of the network layer?

A

The network layer connects different links and LANs into an internetwork and handles routing, and possibly congestion control.

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17
Q

What is the task of the transport layer?

A

The transport layer handles end-to-end data transfer between applications or users in end systems and provides transparency with respect to the underlying transfer technology.

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18
Q

How does the Internet reference model differ from the OSI model?

A

In the Internet model, OSI layers 5 and 6 are merged into the application layer, and OSI layers 1 and 2 are combined into the link/data link layer.

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19
Q

Name the layers of the Internet protocol stack.

A

Application, Transport, Network, Link, and Physical.

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20
Q

Give examples of protocols for the application, transport, network, and link layers.

A

Application: HTTP(S), DNS, SSH. Transport: TCP, UDP. Network: IPv4/IPv6. Link: Ethernet, IEEE 802.11.

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21
Q

Why is there no dedicated security layer in layered architectures?

A

Because security is not explicitly built into the layered architecture as its own separate layer; instead, security mechanisms are added across different layers or protocols.

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22
Q

What does an IP address identify?

A

An IP address identifies an interface, not a host or router as a whole.

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23
Q

Why can a router have multiple IP addresses?

A

Because a router typically has multiple interfaces, and IP addresses are associated with interfaces.

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24
Q

What are the two main parts of an IP address?

A

The higher-order bits form the network part, and the lower-order bits form the host part.

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25
What does CIDR notation like a.b.c.d/x mean?
It means that the first x bits belong to the subnet or network part, and the remaining bits belong to the host part.
26
What are the three overarching security goals of the CIA triad?
Confidentiality, Integrity, and Availability.
27
What is confidentiality?
Confidentiality means that only authorized entities may obtain information during transmission or storage.
28
What is integrity?
Integrity means that data may only be changed by authorized persons or processes during transmission or storage.
29
What is availability?
Availability means that information and services must remain accessible to authorized entities.
30
How do industrial security priorities differ from traditional IT security priorities?
Industrial security typically prioritizes safety first, then availability, integrity, and confidentiality, while traditional IT security usually prioritizes confidentiality, integrity, and availability.
31
Why is safety often ranked above confidentiality in industrial networks?
Because security failures in industrial environments can cause physical damage, safety incidents, and irreparable real-world consequences.
32
What are typical characteristics of industrial systems that make security harder?
Long product lifecycles, rare patching, few adjustments, low-latency requirements, potentially irreparable damage, and the need for emergency or fallback plans.
33
What are the three parts of comprehensive security for industrial networks?
Prevention, Detection, and Response.
34
What is the goal of prevention in industrial security?
Prevention aims to stop or hinder successful attacks and to minimize their possible consequences.
35
What is the goal of detection in industrial security?
Detection aims to identify attacks or suspicious behavior, for example through break-in detection, validity checks, or anomaly detection.
36
What is the goal of response in industrial security?
Response aims to contain damage, clean up systems, and revise the security concept after incidents.
37
How can attacks be classified at a high level?
They can be classified as passive attacks, such as eavesdropping, or active attacks, such as modification.
38
Which attacks target confidentiality?
Eavesdropping and traffic analysis target confidentiality.
39
What is eavesdropping?
Eavesdropping means intercepting messages to gain unauthorized access to information.
40
Why is traffic analysis still dangerous even when data is encrypted?
Because metadata such as addresses, timing, frequencies, communication partners, locations, or used protocols can still reveal sensitive information.
41
Which attacks target integrity?
Modification, masquerading, replaying, and repudiation target integrity-related goals.
42
What is modification as an attack?
Modification means changing intercepted information, including deleting or delaying messages.
43
What is masquerading?
Masquerading, also called spoofing, means impersonating another entity in order to inject or manipulate messages.
44
What is replaying?
Replaying means sending a previously recorded valid message again to the receiver.
45
What is repudiation?
Repudiation means that a sender later denies having sent a message or a receiver later denies having received it.
46
Which attacks target availability?
Denial of service and delay target availability.
47
What is denial of service?
Denial of service interrupts a service for legitimate users, for example by overloading a server, blocking requests, or deleting responses.
48
What is distributed denial of service?
Distributed denial of service uses many distributed resources, such as a botnet, to overload a target.
49
What is a delay attack?
A delay attack artificially delays messages to impair quality of service.
50
Which basic security measures correspond to common threats?
Data confidentiality, data integrity, authentication, non-repudiation, and access control.
51
What is authentication?
Authentication is the assurance that a communicating entity is really the one it claims to be.
52
What is non-repudiation?
Non-repudiation protects against one communication party denying its participation later.
53
What is access control?
Access control prevents unauthorized use of a resource.
54
What are the main technical security building blocks introduced in Chapter 2?
Encryption, integrity protection, digital signatures, authentication exchange, and key agreement.
55
What is encryption?
Encryption encodes information so that unauthorized parties cannot understand it.
56
What is integrity protection?
Integrity protection augments data with a check value so that unauthorized modifications can be detected.
57
What do digital signatures provide?
Digital signatures provide integrity and non-repudiation through a verifiable electronic signature.
58
What is an authentication exchange?
An authentication exchange is a protocol step that proves the identity of one entity to another.
59
What is key agreement?
Key agreement is a mechanism that lets two or more parties agree on a secret key, typically needed for later secure communication.
60
What is symmetric encryption?
Symmetric encryption uses the same shared key for encryption and decryption.
61
What is the main challenge of symmetric cryptography?
The main challenge is secure key distribution: sender and receiver must already share a secret key.
62
What is asymmetric cryptography?
Asymmetric cryptography, also called public-key cryptography, uses different keys for encryption and decryption.
63
What is the main idea behind asymmetric cryptography?
The sender and receiver do not need to share a secret key beforehand; the public encryption key can be known to everyone, while only the receiver knows the private decryption key.
64
Name common examples of asymmetric cryptography.
Diffie-Hellman for key agreement, RSA for encryption and signatures, and elliptic-curve methods for key agreement and signatures.
65
What are the core requirements of public-key encryption?
Decrypting a ciphertext created with the public key must recover the plaintext with the private key, and computing the private key from the public key should be computationally infeasible.
66
What is a digital signature?
A digital signature is a cryptographic mechanism analogous to a handwritten signature that is verifiable and should be non-forgeable.
67
Why is the simple idea of signing a whole message impractical?
Because signing long messages directly is computationally expensive and slow.
68
How is this problem solved in practice for digital signatures?
Instead of signing the whole message, the sender signs a fixed-length cryptographic hash of the message, called the message digest.
69
What is a cryptographic hash function?
A cryptographic hash function maps an input message of arbitrary length to a fixed-length hash value.
70
What is preimage resistance?
Given a hash value H, it should be hard to find a message m such that h(m) = H.
71
What is second-preimage resistance?
Given a message m, it should be hard to find a different message m' with the same hash.
72
What is collision resistance?
It should be hard to find any two different messages that produce the same hash value.
73
Name standardized cryptographic hash functions mentioned in the lecture.
MD5, SHA-1, SHA-2, and SHA-3.
74
What is HMAC?
HMAC is a hash-based message authentication code that combines a shared key and a cryptographic hash function to provide integrity and authenticity.
75
Why is HMAC called a symmetric alternative?
Because both communication parties share the same secret key used for computing and verifying the message authentication code.
76
How are security claims usually expressed for symmetric cryptography?
They are usually expressed in bits and often correspond to the brute-force effort needed to guess the correct key.
77
What does n-bit security mean for symmetric cryptography?
It means an attacker would need about 2^n guesses in a brute-force attack.
78
What is the typical security claim of AES with an n-bit key?
An n-bit AES key provides about n bits of security against brute force.
79
How strong is preimage resistance for a hash function with n-bit output?
It provides about n bits of security.
80
How strong is collision resistance for a hash function with n-bit output?
It provides about n/2 bits of security because of the birthday paradox.
81
How is the security of asymmetric cryptography usually justified?
It is justified by computational hardness assumptions, such as factoring for RSA or discrete logarithms for Diffie-Hellman and elliptic-curve cryptography.
82
Why are quantum computers relevant for cryptography?
Because quantum algorithms can solve certain cryptographic problems much faster than classical algorithms.
83
How do quantum computers affect symmetric cryptography and hash functions?
They weaken them, but the impact can usually be mitigated by increasing key sizes or output sizes.
84
Which quantum algorithm is associated with this weaker but manageable impact on symmetric schemes?
Grover's algorithm.
85
How do quantum computers affect current asymmetric cryptography?
They break the hardness assumptions behind common public-key systems such as RSA and elliptic-curve cryptography.
86
Which quantum algorithm is associated with the severe threat to asymmetric cryptography?
Shor's algorithm.
87
What is post-quantum cryptography?
Post-quantum cryptography uses cryptographic primitives that are intended to remain secure even if large-scale quantum computers become practical.
88
What is one advantage of quantum-resistant algorithms over quantum cryptography like QKD?
They can be used on existing hardware and can serve as drop-in replacements for current cryptographic primitives.
89
What is one drawback of quantum-resistant algorithms?
They are not proven perfectly secure and may still be affected by future quantum discoveries or advances.
90
What is one major drawback of QKD/OTP-style quantum cryptography according to the lecture?
It requires dedicated point-to-point optical fiber connections and has strict keying requirements.
91
Which NIST-standardized post-quantum schemes are named in the lecture for key exchange and signatures?
For PKE/KEM: ML-KEM (CRYSTALS-Kyber) and HQC. For signatures: ML-DSA (CRYSTALS-Dilithium), SLH-DSA (SPHINCS+), and FN-DSA (Falcon).
92
What migration strategy toward quantum-resistant cryptography is suggested in the lecture?
Use traditional and quantum-resistant algorithms in parallel so that security remains intact as long as at least one of the two schemes stays secure.
93
What was the key idea of the TLS post-quantum experiment mentioned in the lecture?
It performed both a traditional and a quantum-resistant key exchange during the TLS handshake and derived one master secret from both shared secrets.
94
What is the trade-off of parallel migration to post-quantum cryptography?
It improves robustness during migration but increases CPU usage, latency, and bandwidth costs.
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