Week 5 and 6 and triad

Question 1

What is message authentication?

Answer 1

A procedure that allows communicating parties to verify that received messages are authentic.

Question 2

What are the physical elements of a One-Way hash Function

Answer 2

Authentication tag: hashed code
The tag generating function: hash function
Function input: the message

Question 3

What are the physical elements of Message Authentication Code (MAC)

Answer 3

Authentication tag: MAC, a small block of data
The tag generating function: MAC algorithm
Function inputs: a secret key (shared by sender and receiver) and the message

Question 4

What are the 3 elements of the CIA triad

Answer 4

Confidentiality
Integrity
Availability

Question 5

What is Confidentiality?

Answer 5

Preserving authorized restrictions on information access
and disclosure, including means for protecting personal privacy and proprietary
information. A loss of confidentiality is the unauthorised disclosure of
information.

Question 6

What is Integrity

Answer 6

Guarding against improper information modification or destruction,
including ensuring information nonrepudiation and authenticity. A loss of
integrity is the unauthorized modification or destruction of information.

Question 7

Availability

Answer 7

Ensuring timely and reliable access to and use of information.
A loss of availability is the disruption of access to or use of information or an
information system.

Question 8

What is a threat?

Answer 8

A potential for violation of security, which exists when there is a circumstance, capability, action, or event that could breach security and cause harm. That is, a threat is a possible danger that might exploit a vulnerability.

Question 9

What is an attack?

Answer 9

An assault on system security that derives from an intelligent threat; that is, an intelligent act that is a deliberate attempt (especially in the sense of a method or technique) to evade security services and violate the security policy of a system.

Question 10

If your data must arrive accurately and in order (e.g., emails, file transfers) what connection type is best?

Answer 10

connection-oriented services are better.

Question 11

What are the disadvantages and advantages of Connection-Oriented Integrity Service?

Answer 11

Requires setting up a connection before communication begins.

Once the connection is established, data is sent and then the connection is closed.

This method is more reliable because it can detect and handle errors, such as message loss or corruption.

Example: TCP (Transmission Control Protocol) ensures data arrives correctly and in order.

Question 12

If speed is more important than reliability (e.g., live video or audio streaming) then which connection method is best?

Answer 12

connectionless services may be acceptable.

Question 13

What are the 6 elements of public-key encryption? Explain.

Answer 13

• Plaintext: This is the readable message or data that is fed into the algorithm as input.
• Encryption algorithm: The encryption algorithm performs various transformations on the plaintext.
• Public and private key: This is a pair of keys that have been selected so that if one is used for encryption, the other is used for decryption. The exact transformations performed by the encryption algorithm depend on the public or private key that is provided as input.
• Ciphertext: This is the scrambled message produced as output. It depends on the plaintext and the key. For a given message, two different keys will produce two different ciphertexts.
• Decryption algorithm: This algorithm accepts the ciphertext and the matching key and produces the original plaintext.

Question 14

Is it possible to perform authentication solely by using symmetric encryption?

Answer 14

encryption does not guarantee integrity or prove the message hasn’t been tampered with.

While this setup can offer some elements of authentication, it is not a complete or reliable solution. Symmetric encryption alone does not guarantee integrity or proper authentication, which is why dedicated methods like Message Authentication Codes (MACs) are preferred.

It might seem that symmetric encryption could be used for message authentication. After all, if only the sender and receiver share a secret key, then only the genuine sender should be able to encrypt a message in a way that the receiver can successfully decrypt and recognize. If the message also includes an error-detection code and a sequence number, the receiver could check that the message hasn’t been altered and is in the correct order. A timestamp could further help ensure the message hasn’t been delayed or replayed.

Question 15

What is the problem with message authentication approaches that do not rely on encryption?

Answer 15

Encryption hides the message (confidentiality) and authentication alone does not do this.
Authentication proves the sender and message integrity.
it is possible to combine authentication and confidentiality in a single algorithm by encrypting a message plus its authentication tag. Typically, however, message authentication is provided as a separate function from message encryption.

Question 16

Explain how to produce Message Authentication Code (MAC)?

Answer 16

The sender uses some publicly known MAC algorithm, inputs the message and the secret key K and produces a MAC value.

Question 17

Explain one-way hash function/secure hash function. (in the context of sending messages)

Answer 17

A one-way hash function is an alternative to a message authentication code (MAC).

It processes a variable-size message (M) and produces a fixed-size message digest (H(M)) as output.

Unlike the MAC, a hash function does not use a secret key.

To authenticate a message, the message digest is sent along with the message, ensuring the digest is authentic.

Question 18

What is a message digest?

Answer 18

encrypted, abbreviated version of a message generated through a hash function.

unique identifier for the message

enhances security - computationally infeasible to decrypt or duplicate the original message.

Question 19

What is SHA?

Answer 19

SHA (Secure Hash Algorithm) is a family of hash functions created by NIST.
* The first version (SHA-0) had flaws.
* It was improved to SHA-1 in 1995.
* SHA is based on earlier algorithms like MD4 and is widely used for secure hashing.

Question 20

What’s the difference between MAC and HMAC?

Answer 20

• MAC is used to check if a message is authentic and unaltered.
• HMAC is a specific type of MAC that uses a hash function and a secret key, making it more secure

Question 21

What are the 6 parts of public-key encryption?

Answer 21

1. Plaintext – the original message.
2. Encryption algorithm – changes plaintext using a key.
3. Public/private keys – one for encryption, one for decryption. the public key of the pair is made public for others to use, while the private key is known only to its owner.
4. Ciphertext – the scrambled message.
5. Decryption algorithm – turns ciphertext back to plaintext.
6. Key pair – the public key is shared, the private key is secret.

Question 22

What is RSA and what are some possible attacks on it?

Answer 22

RSA is a popular public-key encryption system developed in 1977. It uses large prime numbers and is widely trusted.
Attack types:
* Mathematical attacks – try to factor large numbers. Counter: use long keys.
* Timing attacks – analyze how long decryption takes to guess the key. Counter: add delays.
* Chosen ciphertext attacks – trick the system into revealing info. Counter: add padding to the message.

Question 23

What are the uses of public-key cryptosystems?

Answer 23

Encryption/decryption: The sender encrypts a message with the recipient’s public key.

Digital signature: The sender “signs” a message with its private key. Signing is achieved by a cryptographic algorithm applied to the message or to a small block of data that is a function of the message.

Key exchange: Two sides cooperate to exchange a session key. Several different approaches are possible, involving the private key(s) of one or both parties.

Question 24

Can key exchange protocol prevent a man-in-the-middle attack? Explain.

Answer 24

The key exchange protocol is vulnerable to man-in-the-middle attack because it does not authenticate the participants. This vulnerability can be overcome with the use of digital signatures and public-key certificates

Question 25

Public-Key Cryptography - what are the common misconceptions?

Answer 25

Public-key encryption is more secure than symmetric encryption Public-key encryption is a general-purpose technique Key distribution (assignment) is more trivial in public-key encryption Security is depending on key length and computational cost Due to the heavy computational cost of public-key encryption, there’s no evidence showing symmetric encryption will be abandoned

Question 26

Essential steps in public key cryptography

Answer 26

Each user generates a pair of keys (public, privacy) Each user places one key in a public register, which will be the public key Encrypt using one key and decrypt using the other key Note: we can encrypt by either public key or private key Think about these two scenarios Alice wants to broadcast a message to a specific group Alice sends her public key out Alice encrypts by her private key Alice wants Bob to send her an encrypted file Alice gives her public key to Bob to encrypt

Question 27

four famous public-key encryption schemes

Answer 27

RSA Diffie-Hellman DSS Elliptic Curve

Question 28

What is the heartbeat protocol?

Answer 28

The heartbeat protocol is a lightweight method where systems send regular messages to check if the other side is still active. In security, it's used in encrypted connections (like TLS) to keep the session alive and detect failures

Question 29

Common web application attacks (Server-side)

Answer 29

Cross-site scripting (XSS) - Injects scripts into web application server to direct attacks at unsuspecting clients SQL injection - Targets SQL servers by introducing malicious commands XML injection - XML injection occurs when an application does not correctly validate/sanitize user input before using it in an XML document or query.

Question 30

Client-Side Application Attacks

Answer 30

Client-side attacks target vulnerabilities in client applications: Interacting with a compromised server Client initiates connection with server, which could result in an attack One example of a client-side attack is drive-by download, which is a serious threat

Question 31

Name 4 types of firewalls and give a brief description of each?

Answer 31

Packet Filtering Firewall: Checks basic info (IP, port, protocol) of each packet; fast but limited. Stateful Inspection Firewall: Tracks active connections and only allows packets that match a known session; more secure than packet filtering. A stateful packet inspection firewall reviews the same packet information as a packet filtering firewall, but also records information about TCP connections. Application Proxy Firewall (Application-Level Gateway): Intercepts and inspects traffic at the application layer (e.g., HTTP, FTP); very secure but slower. Circuit-Level Proxy Firewall (Circuit-Level Gateway): Monitors TCP handshakes and session-level traffic without inspecting actual content; used to ensure session validity.

Question 32

Security Features of IEEE 802.11

Answer 32

Wired Equivalent Privacy (WEP) - Initial one but weak Wi-Fi Protected Access (WPA) - Wi-Fi standard by the Wi-Fi Alliance - Eliminate most 802.11 security issues - Based on the current IEEE 802.11i standard: IEEE 802.11i: IEEE 802.11 amendment for the security of end-to-end communication Robust Security Network (RSN) - The final form of IEEE 802.11i - WPA2 by the Wi-Fi Alliance – compliance with full RSN requirements

Question 33

How does Diffie-hellman's key exchange work, what are the steps involved?

Answer 33

To parties A and B agree on two numbers where one is the primitive root of the other. Then they each generate private key. Calculates a public key parties exchange keys using one way function. Each party then calculates shared secret key.

Question 34

Why is diffie-hellma key exchange secure?

Answer 34

It is easy to calculate the public key using the agreed-upon public values (like the generator gg, prime pp, and the one-way function formula), but it is infeasible to calculate the private key from the public information, because of the hardness of the underlying one-way function (like the discrete logarithm problem).