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Wireless Networks and Security > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

Security Attack

A

Any action that compromises the security of information

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2
Q

Security Mechanism

A

A mechanism that is designed to detect, prevent, or recover from a security attack

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3
Q

Security Service

A

A service that enhances the security of data processing systems and information transfers. A security service makes use of one or more security mechanisms

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4
Q

What are some examples of Passive Threats?

A
  • Release of message content

- Traffic analysis

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5
Q

What are some examples of Active Threats?

A
  • Masquerade
  • Replay
  • Modification of message contents
  • Denial of service
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6
Q

Name some security services

A
  • Confidentiality (privacy)
  • Authentication (who created or sent the data)
  • Integrity (has not been altered)
  • Non-repudiation (the order is final)
  • Access control (prevent misuse of resources)
  • Availability (permanence, non-erasure)
    • Denial of service attack
    • Virus that deletes files
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7
Q

Methods of Defense

A
  • Encryption
  • Software control (access limitations in a data base, in operating system protect each user from other users)
  • Hardware Controls (smartcard)
  • Policies (frequent changes of passwords)
  • Physical Controls
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8
Q

What are Specific Security Mechanisms?

A
  • May be incorporated into the appropriate protocol layer in order to provide some of the OSI security services
  • Encipherment
  • Digital Signature
  • Access Control
  • Data Integrity
  • Authentication Exchange
  • Traffic Padding
  • Routing Control
  • Notarization
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9
Q

Encipherment

A

The use of mathematical algorithms to transform data into a form that is not readily intelligible. The transformation and subsequent recovery of the data depend on an algorithm and zero or more encryption keys.

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10
Q

Digital Signature

A

Data appended to, or a cryptographic transformation of, a data unit that allows a recipient of the data unit to prove the source of integrity of that data unit and protect against forgery (e.g. by the recipient)

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11
Q

Access Control

A

A variety of mechanisms that enforce access rights to resources.

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12
Q

Data Integrity

A

A variety of mechanisms used to assure the integrity of a data unit or stream of data units.

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13
Q

Authentication Exchange

A

A mechanism intended to ensure the identity of an entity be means of information exchange

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14
Q

Traffic Padding

A

The insertion of bits into gaps in a data stream of frustrate traffic analysis attempts

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15
Q

Routing Control

A

Enables selection of particular physically secure routes for certain data and allows routing changes, especially when a breach of security is suspected

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16
Q

Notarization

A

The use of a trusted third party to assure certain properties of a data exchange

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17
Q

Conventional Encryption Principles

A
  • An encryption scheme has five ingredients:
    • Plaintext
    • Encryption algorithm
    • Secret Key
    • Ciphertext
    • Decryption algorithm
  • Security depends on the secrecy of the key, not the secrecy of the algorithm
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18
Q

Cryptography

A
  • Classified along three independent dimensions:
    • The type of operations used for transforming plaintext to ciphertext
      • Substitution: Each element (bit, letter) in the plaintext is mapped to another element (e.g., B -> F)
      • Transposition: Elements in the plaintext are re-arranged (change locations)
  • The number of keys used
    • Symmetric (singe key)
    • Asymmetric (two keys, or public-key encryption)
  • The way in which the plaintext is processed
    • One block at a time - block cipher
    • Element by element, continuously - stream cipher
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19
Q

Feistel Cipher Structure: Block Size

A

Larger block sized means greater security

20
Q

Feistel Cipher Structure: Key Size

A

Larger key size means greater security

21
Q

Feistel Cipher Structure: Number of Rounds

A

Multiple rounds offer increasing security

22
Q

Feistel Cipher Structure: Subkey Generation Algorithm

A

Greater complexity will lead to greater difficulty of cryptanalysis

23
Q

Feistel Cipher Structure: Fast Software Encryption/Decryption

A

The speed of the execution of the algorithm becomes a concern

24
Q

XOR

A

0 XOR 0 = 0
0 XOR 1 = 1
1 XOR 0 = 1
1 XOR 1 = 0

25
Q

DES

A
  • Data Encryption Standard
    • Block cipher
    • Plaintext is processed in 64-bit blocks
    • The key is 56-bits in length
    • When following the Fesitel structure it is 16 rounds
26
Q

DES Process

A
  • L[i] = R[i-1]

- R[i] - L[i-1] XOR F(R[i-1], K[i])

27
Q

Cipher Block Chaining (CBC) Mode

A
  • Message is divided into several blocks
  • The input to the encryption algorithm is the XOR of the current plaintext block and the preceding ciphertext block
  • Repeating pattern of the 64-bits are not exposed

MAKE SURE TO INCLUDE EQUATIONS AND DIAGRAM ON CHEAT SHEET

28
Q

Location of Encryption Devices

A
  • Link encryption
  • End-to-end encryption
  • High Security
29
Q

Link Encryption

A
  • A lot of encryption devices
  • High level of security
  • Decrypt each packet at every switch
30
Q

End-to-End Encryption

A
  • The source of encrypt and the receiver decrypts
  • Payload encrypted
  • Header in the clear
31
Q

High Security

A

Both link and end-to-end encryption are needed

32
Q

Authentication - Requirements

A

Must be able to verify that

  • Message came from apparent source or author
  • Contents have not been altered
  • Sometimes, it was sent at a certain time or sequence
  • Offer protection against active attack (falsification of data or transactions)
33
Q

Approaches to Message Authentication - Authentication Using Conventional Encryption

A

Only the sender and receiver should know the shared key

34
Q

Approaches to Message Authentication - Message Authentication without Message Encryption

A

An authentication tag us generated and appended to each message
- e.g. Hash without encryption

35
Q

Approaches to Message Authentication - Message Authentication Code (MAC)

A
  • Calculate the MAC as a function of the message and the key.

MAC = F(K,M)

36
Q

Properties of a Secure HASH Function

A

To produce a “fingerprint”

37
Q

Properties of a Secure HASH Function H

A
  • H can be applied to any block of data at any size
  • H produces a fixed length output
  • H(x) is easy to compute for any given x
  • For any given h, it is computationally infeasible to find x such that H(x) = h (one way property)
  • For any given x, it is computationally infeasible to find y not equal to x with H(y) = H(x) (weak collision property)
  • It is computationally infeasible to find any pair (x,y) such that H(x) = H(y) (strong collision property)
38
Q

SHA-1 Steps

A
  1. Append padding bits - the length is 64-bits less than a multiple of 512-bits
  2. Append message length field (64-bits) - The total length is Lx512 bits
  3. Initialize message digest (MD) buffer - A 160-bit buffer is used to hold intermediate and final results of the hash function. The buffer can be represented as five 32-bit registers (A,B,C,D,E), which are initialized to some constant (32-bit integers)
  4. Process message in 512-bit blocks. The heart of the algorithm is a module - compression function, that consists of four rounds of processing, and each round has 20 steps.
39
Q

HMAC (Hash MAC)

A
  • Instead of using encryption algorithms, one may develop a MAC derived from a hash function, such as SHA-1
  • A hash function was note designed for use as a MAC and can not be used directly to create a MAC since it does not rely on a secret key
  • HMAC was proposed, which can create a MAC using a hash function and a secret key
  • HMAC has been used in IP-Security, SSL/TLS, etc.
40
Q

HMAC Motivations

A
  • Faster in software than encryption algorithms such as DES
  • Library code for has functions is widely available
  • No export restrictions on hash functions from the US
41
Q

HMAC Design Objectives

A
  • To use available hash functions
  • To allow for easy replace-ability if the embedded hash function
  • To preserve the original performance of the hash function
  • To use and handle keys in a simple way
  • To have a well-understood cryptographic analysis of the strength of the authorization mechanism
42
Q

Categories of Applications for Public-Key Cryptosystems

A
  • Encryption/decryption: The sender encrypts a message with the recipient’s public key
  • Digital Signature: The sender’s “signs” a message with its private key
  • Key Exchange: Two sides cooperate to exchange a session key
43
Q

RSA Encryption Overview

A
  • Plaintext: M < n

- Ciphertext: C = M^e(mod(n))

44
Q

RSA Decryption Overview

A
  • Ciphertext: C

- Plaintext: M = C^d(mod(n)) = M^ed(mod(n))

45
Q

Requirements for KERBEROS

A
  • Secure: An eavesdropper should not be able to obtain the necessary information to impersonate a user
  • Reliable: Kerberos should be highly reliable and should employ a distributed architecture
    • When Kerberos system itself is under attack, it can still provide authentication service
  • Transparent: Ideally, the user should not be aware that authentication is taking place
  • Scalable: The system should be capable of supporting the large number of clients and servers
46
Q

KERBEROS Realm Requirements

A
  • A server
  • A number of clients
  • A few application servers
47
Q

Purpose of X.509

A

X.509 defines a framework (certificate structure) for authentication services by the X.500 directory to its users

  • The directory may serve as a database of public-key certificate
  • Each certificate contains the public key of a user and is signed with the private key of a trusted Certificate Authority (CA)
  • The heart of X.509 is the public-key certificate associated with each user

Wireless Networks and Security (1 decks)

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