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Information Security > Midterm # 2 > Flashcards

Midterm # 2 Flashcards

1
Q

Authentication is?

A

The process of determining whether a user should be allowed access to a system.

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2
Q

Authentication question?

A

are you who you say you are?

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3
Q

authorization

A

are you allowed to do that?

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4
Q

The three authentication methods?

A

Something you know
Something you have
Something you are

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5
Q

How to prevent forward search attack

A

To prevent a forward search attack on a public key encryption we append random bits to the message before encrypting it

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6
Q

Salt?

A

Appending a non secret random value known as salt to each password before hashing it.

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7
Q

What is a salt?

A

a non secret value that causes identical password to hash to different values

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8
Q

What is a two factor authentication?

A

any authentication method that requires two out of the three “somethings” is known as a two factor authentication

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9
Q

what is the common criteria?

A

EAL1 through EAL7

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10
Q

what is EAL1

A

functionally tested

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11
Q

what is EAL2

A

Structurally Tested

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12
Q

What is EAL3

A

Methodically Tested and Checked

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13
Q

What is EAL4

A

Methodically Designed, Tested, and Reviewed

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14
Q

What is EAL5

A

Semiformally Designed and Tested

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15
Q

What is EAL6

A

Semiformally Verified Design and Tested

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16
Q

What is EAL7

A

Formally Verified Design and Tested

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17
Q

What are ACL’s?

A

Access control lists, columns

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18
Q

What is C-lists?

A

Capabilities, rows, subject trying to perform an operation

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19
Q

What are the advantages of capabilities?

A

with capabilities the association between users and files is built into the system. Capabilities are more complex to implement, and have higher overhead

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20
Q

what are the advantages of ACL

A

ACL based system, which is a separate method for associating users to files is required.

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21
Q

what is the confused deputy?

A

the confused deputy is a classic security problem. fooled by some other party into misusing its authority. the compiler is acting on Alice’s behalf.

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22
Q

Classification applies to…

A

Objects

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23
Q

Clearances apply to…

A

Subjects

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24
Q

Classification and Clearances order?

A

Top Secret
Secret
Confidential
Unclassified

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25
Q

what is BLP

A

Bella-LaPadula

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26
Q

What is Bella-LaPadula

A

is to capture the minimal requirements with respect to confidentiality, that any MLS system must satisfy

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27
Q

BLP consists of two statments

A

Simple Security Condition,

Property

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28
Q

What is Simple Security Condition

A

Subject S can read object O if and only if L(O) <= L(S)

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29
Q

What is Property

A

Star property, Subject S can write objects O if and only if L(S) <= L(O)

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30
Q

what is the point of compartments?

A

to further restrict information flow “across” security level, compartments enforce he need to know principle.

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31
Q

what is a covert channel?

A

communication path

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32
Q

what is captcha?

A

is a test that a human can pass, but a computer can not pass with a probability better than guessing.

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33
Q

what does firewall provide?

A

firewall provides access control for the network. Each type of firewall filters packets by examining the data up to a particular layer of the network protocol stack.

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34
Q

What are the five layers of packet filter?

A

application, transport, network, link, physical

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35
Q

what is the advantage of a packet filer

A

efficiency

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36
Q

concept of firewall?

A

firewall has no concept of state so each packet is treated independently of all others.

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37
Q

what do packet filters use?

A

they are configured using access control ists or ACLs

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38
Q

what is a port scan?

A

Trudy tries to determine which ports are open through the firewall

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39
Q

Application proxy?

A

the incoming packet is destroyed and a new packet is created in its place when the data passes trough the firewall.

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40
Q

Protocol what is bad?

A

it is a bad idea to have the two sides in a protocol do exactly the same thing, since this might open the door to an attack. small changes to a protocol can result in big changes in its security.

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41
Q

Remember..

A

You should not use the same key pair for signing as you use for encryption

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42
Q

how prevent MiM attack?

A

Alice and Bob can use their shared symmetric key K_AB, to encrypt the diffie hellman exchange

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43
Q

what is timestamp?

A

a time value

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44
Q

what is the benefit of timestamp?

A

is that we do not need to waste any messages exchanging nonces, assuming that the current time is known to both Alive and Bob.

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45
Q

Zero knowledge proofs

A

bobs cave which side

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46
Q

what is Fiat shamir?

A

relies on the fact that finding a square root modulo N is as difficult as factoring.

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47
Q

Why is it better to hash passwords with a salt than to hash passwords without a salt?

A

Not a secret, stored with passwords
dictionary attack more difficult
it creates more work for hacker
hacker can not use precomputed work.

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48
Q

why do we hash passwords with a salt rather than encrypt the password file?

A

store you have to encrypt the key, if you get the password file you get the key.
Password file is a single point of failure

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49
Q

What purpose do timestamps and nonces serve?

A

challenges used to verify authentication session PREVENT REPLAYS

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50
Q

Advantage of timestamp as compared to a nonce?

A

MORE EFFICIENT

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51
Q

One significant disadvantage of timestamp as compared to nonce?

A

CLOCK SKEW

time is a security concern

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52
Q

Lampson’s access control matrix, capabilities?

A

C-lists, rows and describe permissions for subjects

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53
Q

Lampsons access control matrix, ACLs?

A

Access control lists, are columns

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54
Q

2 advantages of C-lists over ACL’s

A

Easy to add or delete

easy to delegate permissions

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55
Q

2 advantages of ACLs over C-lists

A

Easier to implement

Easy to change permissions

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56
Q

Differences between Authentication and identification?

A

One to one VS one to many

subject compliance VS non subject compliance (data)

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57
Q

Which is easier and why? authentication or identification?

A 
authentication is easier:
   Only one way for authentication
   Already know i am authenticating 
  Comparisons to ONE
with identification one to many, comparisons depends on data
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58
Q

Packet fileter

A

works at the network layer, attacker uses TCP ACK scan

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59
Q

Stateful packet fileter

A

works at the transport layer, attacker uses firewalk to send packets.

60
Q

what is firewalk

A

to check for port opening, port scanning

61
Q

Application proxy

A

works at the application layer, DLS attack can perform a port scanning

62
Q

MIG

A

if bob and alice are doing the same thing you can get MIG

63
Q

Method used to prevent covert channels are inherently weak. Is it better to use such weak methods or to do nothing at all?

A

better fuse weak , reduces bandwidth, EASY TO DO RELATIVELY

64
Q

methods used for inference control are inherently weak. is it better to use weak or nothing?

A

Weak, reduces data leaks, EASY TO DO RELATIVELY

65
Q

suppose that the only cryptosystem you have access to is known to be weak is it better to use this system to encrypt your data or to do nothing at all?

A

Do nothing at all , because you could flag it as import since the system is weak.

66
Q

Why do we hash passwords that are stored in a password file?

A

so if the password file is stolen or accessed by trudy they can not determine the passwords and use it to log in to that system or other resources.

67
Q

Why is it better to hash passwords than to encrypt the password file with a symmetric cipher?

A

hashes are one way and do not require that we decrypt any password files. Decrypting a password file would require that the key to be stored some where so that the system can automatically decrypt the file when verifying password. creates a security problem as to where to store the key.

68
Q

Time stamps and nonces

A

are both used in security protocols to prevent replay attacks

69
Q

Advantage of timestamp as compared to a nonce?

A

less messages required to achieve authentication as the nonce does not need to be exchanged.

70
Q

Advantage of nonce as compared to timestamp?

A

Time stapts in the first case are security critical parameter and require a window of “opportunity” to account for clock skew. Nonce do not have that and it is a disadvantage.

71
Q

One significant advantage of packet filter as compared to a stateful packet filter.

A

fast, less overhead s it does not monitor the state. stateful keeping track of state of lots of connections

72
Q

Significant advantage of stateful packet filter as compared to packet filter.

A

prevents simple TCP ACK attack on firewall to determine if ports are blocked as the firewall will know that there is no valid session or state and reject the packet.

73
Q

cost passwords are…

A

free

74
Q

connivence passwords are…

A

easier for admin to reset pwd than to issue a new thumb

75
Q

ECB

A

same plain text and same ciphertext

76
Q

forward search prevented

A

padding with random bits prevents forward search attach, can not use a precomputed set of passwords, more work for trudy

77
Q

No salt No dictionary

A

brute force, hash it and compare to all the passwords

78
Q

yes salt

A

talk the salt hash it and compare work

79
Q

work

A

size of dictionary / prob passwords in dictionary

80
Q

2^10

A

1024

81
Q

web cookies

A

cookie is provided by a website and stored on users machine, cookie indexes a database at website, cookies maintain STATE across sessions

82
Q

web uses a what protocol

A

a stateless protocol HTTP

83
Q

authorization is a form of

A

access control

84
Q

ACL

A

Access control lists store matrix by column

85
Q

ACLS

A

permissions tied to a file

86
Q

capabilities

A

permissions tied to the user

87
Q

ACLS

A

easier in changing files

88
Q

Confused deputy

A

complier is acting on alices behalf, confusing her permission with Alice’s permissions overriding a bill for example

89
Q

in practice…

A

ACLs are used more often

90
Q

capabilities make it …

A

easy to delegate authority

91
Q

Classifications apply…

A

to objets ressources

92
Q

Clearances apply…

A

to subjects users

93
Q

MLS is needed

A

when subjects and objects at different levels use on same system

94
Q

MLS is a form of

A

Access Control

95
Q

MLS enforces

A

Multilevel security enforces access control up and down

96
Q

compartments enforce

A

enforce restrictions across, the need to know principle

97
Q

Cover Channel

A

MLS designed to restrict legitimate channels of communication

98
Q

Covert channel

A

desecrate means of communication, 1 it is there , 0 it is not there

99
Q

a firewall is like a…

A

secretary

100
Q

packet filter operates at the

A

network layer

101
Q

stateful packet filter

A

operate at the transport layer, firewall will keep track then it can drop it

102
Q

packet filer disadvantages

A 
no concept of state
cannot see TCP connections
blind to application data
less information to go on
on going connections we do not see it just like ARP cacheing
103
Q

dis advantage of stateful packet filter

A

can not see application data
slower than packet filtering
more work
state DoS is an issue

104
Q

what is a proxy

A

something that acts on your behalf

105
Q

Application proxy disadvantages

A

speed more work DoS

106
Q

Application proxy advantages

A

complete view of connections and applications data

Filter bad data at application layer

107
Q

webcookies make a

A

stateless protocol

108
Q

application –>

A

user space

109
Q

transport –>

A

os

110
Q

network –>

A

os

111
Q

link

A

NIC card

112
Q

Physical

A

NIC card

113
Q

client

A

speaks first

114
Q

server

A

responds to clients request

115
Q

spoofed email doesn’t have

A

authentication

116
Q

UDP is

A

efficcent

117
Q

TCP is

A

reliability

118
Q

compartments help

A

need to know bases

119
Q

UDP

A

certain delays long or short packets

120
Q

botnet

A

compromised machines

121
Q

botnet

A

can do DoS an spam

122
Q

inference control

A

not too difficult to do

123
Q

captcha the attacker

A

the attacker knows the algorithm, the data, except the random numbers

124
Q

TCP 3-way

A

the TCP 3-way handshake makes denial of service DoS attacks possible

125
Q

TCP three way handshake

A

first send SYN request
BACK SYN-ACK
ACK and data

126
Q

ARP is

A

stateless

127
Q

Ideal security protocol

A

Efficient
Precise
Robust
easy to implement, easy to use ,flexible

128
Q

security protocol over a

A

Network layer, sending important information over the network back and forth attacker can replay messages.

129
Q

challenge response

A

prevents replay, only alice can respond to properly Bob has to verify it. Number used one is a Nonce

130
Q

Number used once

A

Nonce

131
Q

another version of nonce

A

timestamps

132
Q

diffie hellman

A

man in the middle has to happen in real time

133
Q

nonce

A

generate it and send it current to prevent replay

134
Q

Time stamp disadvantage

A

synchronization of clocks, network delay

135
Q

Nonce

A

3 messages

136
Q

timestamp

A

2 messages

137
Q

Encrypt and sign with timestamp…..

A

insecure

138
Q

sign and encrypt with nonce

A

secure

139
Q

encrypt and sign with nonce

A

secure

140
Q

sign and encrypt with timestamp

A

secure

141
Q

Fiat shamir what is x

A

x = r^2 mod N

142
Q

fiat shamir what is y

A

y = r * s^e mod N

143
Q

fiat shamir what is v

A

v = S^2 mod N

144
Q

what does bob verify in fiat shamir

A

y^2 = x * V^2 mod N

145
Q

fiat shamir wha tis y ^2

A

y^2 = r ^2 * S ^(2e)

Information Security (5 decks)

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