Authentication and access control

Question 1

Define closed design

Answer 1

A type of design where the actual algorithms, and implementation itself are kept secret.
However, secrecy is not the same as security, and a closed design will not be considered secure just because of the secrecy aspect.

Question 2

What is open design (Kerckhoffs principle) ?

Answer 2

The implementation, design pattern or algorithm themselves are known, but the system uses a secret input (a key) that is required for en- and decryption.
This allows for algorithms to be public without causing any data leak

Question 3

What is cryptanalysis?

Answer 3

A type of attack where an attacker tries to find out the secret key.
An example is when the attacker has access to the plain text and the ciphertext, and attempts to figure out the key based on these.

Question 4

What is a brute force attack?

Answer 4

A cryptanalysis attack where an attacker tries to guess a secret key by checking all possible keys.

Question 5

How can you protect against brute force attacks?

Answer 5

Making sure the key space is so big that an attacker wouldn’t be able to go through them all.

Question 6

What happens during a man-in-the-middle attack

Answer 6

If we have to subjects, A and B, communication. A third subject C can place themselves in the middle of A and B, and by doing they pretend to be subject B for A, and pretends to be subject A for B.

Question 7

What is symmetric key cryptography?

Answer 7

The sender and the receiver share a common key.
Encryption and decryption is done by using this key.

Question 8

What are the main functions of symmetric key cryptography?

Answer 8

Need a routine, or a way, of generating the shared key.
Need a safe channel to communicate the key between the two trusted parties
Routine for encryption
Routine for decryption

Question 9

What is One Time Pad?

Answer 9

The key is the length of the plaintext, and randomly generated.
Exclusive “or” is used on the plaintext from the key.
If an attacker tries to compute a message from the ciphertext, they wouldn’t know when they have the original message. Every possible message that can be computed from the cypher text is just as likely to be the plaintext.
Provides complete secrecy in theory

Question 10

Why is the One Time Pad not widely used?

Answer 10

The burden of creating the keys itself is so big that it is no longer practical.

Question 11

What algorithms is a symmetric cryptography cryptosystem composed of?

Answer 11

KeyGen(L): Key generating algorithm, L: length of key
Enc(K,M) -> C: Encryption algorithm, K:Key, M:Message, returns C:Ciphertext
Dec(K,C) -> M: Decryption algorithm: K: Key, C: Ciphertext, M:Message

Question 12

Describe the Caesar cipher(Shift cipher)

Answer 12

Each letter is shifted a certain number of places down the alphabet.
Enc = M + K(mod 26)
Dec = C - K(mod 26)

Question 13

Why isn’t the Caesar cipher secure?

Answer 13

Small key space - number of letters in the alphabet

Question 14

What is DES (Data encryption standard)?

Answer 14

Internal structures: Feisel, S-boxes, permutations, shifts, XORs
Should not be used - not secure

Question 15

What is triple DES?

Answer 15

An decryption algorithm using three DES operations

Question 16

What is AES (Advanced encryption standard)?

Answer 16

Todays standard when using symmetric cryptography

Question 17

Name 6 symmetric key ciphers, and what they are used for.

Answer 17

IDEA: Used in PGP
Blowfish: Password hashing in OpenBSD
RC4: (used in WEP), RC5
Double DES, Triple DES
SAFER: Bluetooth
AES: Pervasive

Question 18

What is asymmetric cryptography (public key cryptography)?

Answer 18

Every user has two keys
Public key (E): Released to everyone who wants to send a message, used for encryption
Private key (D): Known only to the user using it, used for decryption
The need to share secrets between the communicating parties is alleviated.

You release your public key to the world. People use the public key to encrypt the messages. Only you, with the private key, can decrypt the messages.

Because of how the decryption- and encryption systems work with public key cryptography, these processes are slower than during symmetric key cryptography

Requires very large key spaces. This is because there aren’t that many prime numbers. Minimum 2048 bit key space

Question 19

What are two problems with symmetric cryptography, that asymmetric cryptography alleviates?

Answer 19

When using symmetric cryptography system, the communicating subjects first need to share the key over a channel, meaning it is very important to ensure this channel is safe. When using public key cryptography there is no need to share keys, removing this problem.

Also, for every N subjects that want to communicate, there is a need for N squared keys in the system. This number will increase quickly

Question 20

What concept is very important in asymmetrical cryptography, and widely used in asymmetrical cryptography algorithms,

Answer 20

If you have a very large prime number, that is a product of two other primes, it is very difficult to figure out which two primes make up the factors.

For example, a private key would contain information about the two primes, whereas the public key could be any number which would later be used to compute inverses.

Question 20

What concept is very important in asymmetrical cryptography, and widely used in asymmetrical cryptography algorithms,

Answer 20

If you have a very large prime number, that is a product of two other primes, it is very difficult to figure out which two primes make up the factors.

For example, a private key would contain information about the two primes, whereas the public key could be any number which would later be used to compute inverses.

Question 21

What is the components of an asymmetric cryptography system?

Answer 21

KeyGen(L): Return K_pub, K_priv
Enc(K_pub, M) -> C
Dec(K_priv, C) -> M

NB: given K_pub, it is extremely difficult to compute K_priv

Question 22

How does digital signatures work?

Answer 22

Encryption is done by using a private key, and decryption is done by using the public key.

C = Enc(K_priv, M)
M = Dec(K_pub, C)

This means that everyone can in fact read the message sent, as everyone will have access to the public key. However, no one would be able to substitute the original message with their own, as they do not have the private key to encrypt their own message.

Because of this, digital signatures can be used to confirm the identity of the sender.

Digital signatures work slow

Question 23

What are the properties of cryptographic hash functions?

Answer 23

• Can apply to data of any length
• Output is fixed length
• Relatively easy to compute h(x), given x
• Deterministic, given the same x - h(x) will always output the same
• One-wayness property: Infeasible to get x, given h(x)
• Weak-collision resistance property: Given x, infeasible to find y such that h(x) = h(y)
• Strong-collision resistance property: Infeasible to find any pair x and y, such that h(x) = h(y).

Question 24

How often does collisions occur?

Answer 24

For a hash of length n bits, a collision can be found in 2^(n/2) trials

Question 25

How is hashes and digital signatures combined?

Answer 25

As creating a digital signature for a large message is an expensive process, we first create a hash of the data, and then a digital signature of that hash. The clear text message is then sent along with the signed hash value of the text. h = H(m), hash of message S = Enc(K_priv, h), hash signature The reciprient can then calculate the hash of the message and see if it matches: h = H(M)

Question 26

What is PKI? (Public key infrastructure)

Answer 26

A system for key distribution. A PKI is a trusted server that will create signatures and sign things for their users. Digital certificates are one of the fundamental building blocks of PKI.

Question 27

What is digital signatures?

Answer 27

A mathematical scheme for verifying the authenticity of digital messages and documents. A digital signature upholds properties of both authentication and integrity, by providing a strong reason for the recipient to know that the message indeed came from the given sender, and that the message was not altered in transit.

Question 28

Describe the steps of signing some data with a digital signature.

Answer 28

Data -> hash function -> hash S = Enc(K_priv, hash), create signature by encrypting the hash Send signature + data = Digitally signed data

Question 29

Describe the steps of verifying data that is signed with a digital signature.

Answer 29

First run the data through the has function. H(M) = h Then decrypt the signature with the signers public key. Dec(S, K_pub) = h Check if the two hashes are equal, only then can the data be verified

Question 30

What is a digital certificate and what does it contain?

Answer 30

An electronic document proving ownership of a public key. Contains: - Information about the key - Information about the identity of the owner (subject) - The digital signature of an entity that has verified the certificate's contents (issuer)

Question 31

How is digital certificates used in PKI systems

Answer 31

PKI servers does not only need to verify who a message came from. They also need to provide information about the public keys themselves. For example, if and key have an expiration date, and when this might be. A CA (Certification Authority) signs digital certificates and attest for the key and give information about this key. This information includes things like - why you know that this is a certain subject's key. - Who issued them - Version number

Question 32

How can PKIs be structured in a hierarchical way?

Answer 32

Have one CA that gives out certificates to all serves, devices and computers you want to issue them for. CA -> User certificate, Server certificate, Device certificate In practice, it is too burdensome for only one CA to handle all the certificates, making it more practical to implement multi-level hierarchies. The root CA has the authority to issue certificates for certain entities. This entities can their own CA's that can issue certificates to other sub-entities Root CA -> CA_1, CA_2, User CA_1 -> User_1, User_2, User_3 CA_2 -> User_4, User_5, User_6 PKI's can use cross-certification, where two CA sign for each other. Trusting one of them will automatically lead to trusting the other CA_1 - CA_2 CA_1 -> user1, user2, user 3 CA_2 -> user4, user5, user6 PKI's can use bridge CA, where one CA acts as a bridge that certifies all the other CA's, and all the others certify the bridge

Question 33

How is certificates validated in practise where multi-level CA hierarchies are used?

Answer 33

The software will use Trust Path Building. The software that is going to validate the certificate (browsers, etc..) are often pre-installed with a set of trusted certificates. The software will then see if it can find a path of certificates from one of the certificates it trusts, down to the certificate the software is trying to get to. (Follow a chain of trust).

Question 33

How is certificates validated in practise where multi-level CA hierarchies are used?

Answer 33

The software will use Trust Path Building. The software that is going to validate the certificate (browsers, etc..) are often pre-installed with a set of trusted certificates. The software will then see if it can find a path of certificates from one of the certificates it trusts, down to the certificate the software is trying to get to. (Follow a chain of trust)

Question 34

What is cross certification?

Answer 34

Cross certification is when two CA's sign for each other. Meaning, that if either of them is in a system's trusted CA's, you will be able to follow a trust path from them

Question 35

What is Bridge CA?

Answer 35

When one CA operates as a hub, or a bridge CA, that sits in the middle of a lot of trust relationships. Meaning it validates a lot of CA's and all the other CA's certifies this bridge. This structure does put a lot of paths through one CA, potentially causing issues

Question 36

What components does PKI's contain?

Answer 36

Certificate authority (CA): Responsible for issuing certificates Registration authority (RA): Verifies the identity of the individual requesting a certificate Certificate repository and revocation information: Hold information about which certificates are still valid

Question 37

What does the registration authority do in PKI's?

Answer 37

Verifies the identity of the subject requesting a certificates. Tries to figure out why we would belive that the subject is who they say they are. A subject or user would communicate directly to the registration authority by providing authentication of who you are, so you can obtain a certificate. How this authentication happen varies based on what type of certificate you are getting. Registration authorities can be people but also machines and software

Question 38

In what situations would it be necessary to revoke a certificate?

Answer 38

If private keys have been compromised. Certification information is no longer valid. KeyGen algorithm has been proven insecure. Encryption algorithm has been proven insecure.

Question 39

What is a Certificate Revocation List (CRL) ?

Answer 39

A certificate that list who you revoke trust in. For each certificate in the list, its serial number, the time of revocation and reason for revocation is listed. The CA will then sign it and communicate that these should no longer be trusted. A system would need to download this list. The CRL contains information about the key, which trust should be revoked, revocation data and signature. Is released at a CDP (CRL Distribution Point)

Question 40

Describe the revocation timeline

Answer 40

Key compromise event - Certification revocation request - CA signs Certificate revocation - new CRL is issued communicating to users the certificate can't be used

Question 41

What are some issues with CRL's?

Answer 41

The revocation process takes a lot of time, burdensome, doesn't work well in practise. CRL's can be generated very slowly because of how some CA's may operate.

Question 42

What is the Online Certificate Status Protocol (OSCP)?

Answer 42

A server tells you if a certificate has been revoked. Preferable compared to CRL's

Question 43

What are some issues with OSCP?

Answer 43

Additional cost for having the system be online all the time. Certificates being stale

Question 44

What does CA's do (Certificate authority)?

Answer 44

Do not generated keys. Organisations will generate keys, and then go to a CA to prove that they own that key-pair. CA's will then provide and sign the organisation a certificate that states that the organisation does in fact own that key pair.

Question 45

Define authentication

Answer 45

Authentication is when you prove your identity to another actor

Question 46

What is the 3-step challenge-and-response process in authentication

Answer 46

User claims an identity (often by providing a username) The server challenges the user by asking for a password The user supplies this password as proof of identity

Question 47

What are the three categories of authentication?

Answer 47

1. Something you have 2. Something you are 3. Something you know

Question 48

Describe the "Something-you-have" chategory of authentication

Answer 48

A person wouldn't leave their home without their phone. Because of this the phone can be used as a form of authentication, just because of the fact that you would always bring it. When you have the key to your house, you authenticate that you in fact are the owner of the house. Drawback: Phone/key could be stolen

Question 49

Describe the "Something-you-are" category of authentication

Answer 49

Use biometrics to identify Face, fingerprints, DNA, voice recognition

Question 50

Describe the "Something-you-know" category of authentication

Answer 50

Passwords It's very scalable and people understand how to use them well. Drawbacks: - Difficult to create strong passwords, password reuse - People can figure out you password (look over your shoulder, etc.)

Question 51

How are passwords stored

Answer 51

Only the password hash is stored

Question 52

How did passwords use to be verified?

Answer 52

A password has was stored on creation. During authentication, a user provides the password and its hash is then compared to the hashed stored. Only if the hashes are identical, authentication would be granted. Drawbacks: - Vulnerable to Dictionary attacks: Someone creates a dictionary of common passwords and their hashes. If there is a memory leak of passwords, you can then compare the hashes to the ones in the dictionary and by that figure out the passwords.

Question 53

What are rainbow tables?

Answer 53

Uses pre-computed hash chains (hash-reduce-hash-reduce...) - You have the original hash function - You have a reduce function (does not invert the hash. Takes the hash and reduces it to some plain text - not the original though) Only the first and the last word of the hash chain is stored (start word and the final reduced word)

Question 54

How does the rainbow table algorithm work?

Answer 54

You have a hash, and want to find the password for this hash. Reduce the hash (this gives you some plaintext) Compare with endpoint in rainbow table Hash and reduce until the endpoint is found Entry found, load starting value Hash and reduce the starting value until the hash is the same as the hash you started with in the beginning (the provided hash value is found) The final reduced value is the password - the word that gave the hash

Question 55

How do we defend against rainbow tables?

Answer 55

Salt hashes Salts are random values that are put with the plaintext password, before the password is hashed. What is stored is the random salt and the hash. An attacker can no longer pre-compute the hashes of common paswords

Question 56

How are salted password verified?

Answer 56

A plaintext password is provided with the stored salt. These are then hashed and compared to the stored hash.

Question 57

What is a common issue with authentication by something we know?

Answer 57

Weak password, password reuse Attacks: Dictionary attack, rainbow table attack

Question 58

How can we nudge users into using better passwords?

Answer 58

Enforcing password policies (min 8 signs, upper and lowercase, ...)

Question 59

What are todays threats to passwords

Answer 59

Phising Malware Online bruteforce (go to a site and trying passwords until you find the right one) Offline brute force attacks

Question 60

Describe offline password attacks

Answer 60

The password file must leak and be undetected - If leak is detected - the password can be reset and the offline attack is ineffective The leak can result in you getting: - Plaintext password (offline attack unneeded, you have the password) - Unsalted and hashed (Rainbow table lookup) - Salted and hashed (Offline bruteforce attack) - Reversibly encrypted (decryption key leak: offline attack unneeded - have plaintext, decryptioin key unleaked: offline attack not possible)

Question 61

What is an offline bruteforce attack

Answer 61

Password attack used on hashed and salted passwords. Can be mitigated by having strong, and long passowrds.

Question 62

What are password meters?

Answer 62

Indicators of how strong a password is. Giving feedback to the user during creation time

Question 63

What are some of the results found of using password meters

Answer 63

Users choose longer passwords Decrease guessability of passwords

Question 64

What are graphical passwords?

Answer 64

Three different approaches: - recognition: presented with different images, and you must remember your own recall: user remember their visual cued recall: prompted with a picture and then have to interact with it Advantage: - Easier to remember images than words - Visual objects seems to offer a larger set of usable passwords

Question 65

What are som weaknesses with graphical passwords

Answer 65

Interaction with photos are psychological and culturally biased - behaviour can be predicted Make FOA maps (focus-of-attention): Images can be prosessed and estimate where the image is likely to be clicked

Question 66

What is a FOA map?

Answer 66

Focus-of-attention map Gives probability of each estimated click point on an image Calculated probability based on low-level properties (contrast, color)

Question 67

What is biometric authentication

Answer 67

Something-we-are Biometric: Biological characteristic that can identify an individual Authentication based on identifying characteristic of the user (face, fingerprint, voice, ...) Two groups: behavioural biometrics and physical

Question 68

What are the 4 properties that qualifies something to be a biometric?

Answer 68

Universal (everyone must have it) Distinctiveness (limited to you, nobody should have the same as you) Permanence (the characteristic should stay the same over time) Collectability

Question 69

What are some issues in a practical biometric system

Answer 69

Performance: If the system takes a long time to log in, nobody would want to use it Acceptability: The biometric must be acceptable, nobody would want their DNA to be used to log into facebook Circumvention: The biometric system shouldn't be able to be circumvented. I.e if you don't have a camera and a fingerprint scanner - just use your password. The system is now circumvented. Biometric systems are in practise pattern recognition systems: the biometric will not be exact every time it is measured (noice in sensor, noice in biometric - dirty fingerprint). The system must allow biometrics that are close enough to the original to be accepted

Question 70

Which requirements should a biometri system meet?

Answer 70

Accuracy speed resource requirement Harmless to user accepted by intended population sufficient robust to various attacks

Question 71

What is the pipeline of a biometric system

Answer 71

Sensor module Feature module: Take raw data and extract meaning from it Matcher module: Try to find a match in the database System database module: Stores biometric

Question 72

What is the verification mode of a biometric system?

Answer 72

The user provides an identity and a biometric to prove the identity. System checks if biometric belong to the identity provided login -> feature extraction -> matcher <- System database sends ONE template

Question 73

What is the identification mode of biometric systems?

Answer 73

No identity is being claimed, only the biometric is sent. The system will check if the biometric is stored in the database login ->feature extraction -> matcher <- database sends N template

Question 74

What errors can occur in biometric systems?

Answer 74

Can get a false match: The biometric matches the wrong individual Can get a false non-match: The biometric doesn't match the true identity FTC: Failure to capture (sensor doesn't et a good enough reading) FTE: Failure to enroll (provided data doesn't give a good enough match that a security decision can be made)

Question 75

Name one way biometric systems are different from passwords

Answer 75

The system aren't looking for an exact match, in a way passwords has to be exact. The system will use pattern recognition to find a match that is close enough

Question 76

In what way does biometric systems use hypothesis

Answer 76

H_0: Input X_Q does not come from the same person as the template X (this is the null-hypothesis) H_1: Input X_Q comes from the same person as the template X (the alternative hypothesis) The system then make decisions based on the hypothesis: - D_0: person is not who they claim to be - D_1: The person is who they claim to be Look at input: S(x_Q, X_I) >= t, then D_1, else D_0 (If the similarities between the input and the template is above a threshold)

Question 77

Define a false match in mathematical terms

Answer 77

D_1 when H_0 The decision D_1 (person is who they claim to be) is made when in reality the null hypothesis H_0 is correct

Question 78

Define a false non-match in mathematical terms

Answer 78

D_0, when H_1 The decision D_0 (person is not who they claim to be) is made when in reality the alternative hypothesis H_1 is correct

Question 79

What is FMR?

Answer 79

The probability o a false-match error happening is biometric systems FMR = P(D_1 | H_0)

Question 80

What is FNMR?

Answer 80

The probability of a false non-match error happening in biometric systems FNMR= P(D_0 | H_1)

Question 81

What is behavioural biometrics

Answer 81

How you talk, walk, type, etc...

Question 82

What are the three groups of application of biometric systems

Answer 82

Commercial (What users use often, credit card, cellular phone, atm) Government (id card, drivers licence, passport control, hightened threat model ) Forensic (terrorist identification, missing person)

Question 83

What are some disadvantages with using biometric systems?

Answer 83

Speed: Can be slow to compute FMR will increase when scaling up the amount of users Irrevocability - if a data leak happens, people can't change their biometrics

Question 84

What are some limitations of unimodal biometric systems

Answer 84

- Noise in sensed data - Distinctiveness: The first measure might not be distinctive. E.g if you only measured parts of you fingerprint - Spoof attacks: Your biometric gets measured and stored somewhere else and then put to use (fingerprint on glass)

Question 85

What are multimodal biometric systems

Answer 85

Take multiple measurements of biometric and combine them This fusion can happen on sensor level, feature, opinion or decision level

Question 86

What three combination strategies can be used in multimodal biometric systems

Answer 86

Fixed rules: Everything gets equal weight Trained rules: Uses different classifiers, unequal weight Adaptive rules: Adaptive weight

Question 87

What are som issues with decision level fusion?

Answer 87

During decision level fusion, each classifier has defined a class for the measurement, or given weight to the possible classes based on the measurement. When combining the output from the different classifiers there might be some ties

Question 88

What is AND-combination?

Answer 88

Improves the False-Acceptance-Ration System 1 -> AND -> System 2 The AND must be true Ex. fingerprint AND face must match

Question 89

What is OR-combination?

Answer 89

Improves the False-Rejection-Ration Either this OR this

Question 90

How can you mitigate data leakage in biometric systems

Answer 90

A problem with biometric data leaking is that it is inrevokable. A person cannot get a new DNA or a fingerprint. To protect against this template protection can be used. Here, the biometric is measured by the sensor, registered and then processed before it is stored. If a leakage would occur, the processed template would leak and not the biometric itself. This template is revokable, because you can change the method for processing the template.

Question 91

What are the three categories of template protection?

Answer 91

Straight feature protection Key-generating Key-binding

Question 92

What is straight feature protection?

Answer 92

Protect the features by using a transformation on the biometric. The template stored is an irreversible transformation of the biometric

Question 93

What is key generating

Answer 93

The biometric goes into a keyGen or hashing algorithm, and out comes a key

Question 94

What is key binding?

Answer 94

Biometric cryptosystem that binds key data with the biometric data. You generate a random key at enrollment, and mix that with the biometric in a way that is reversible. During verification, you supply the biometric to the template and remove it to see if you are left with the correct key.

Question 95

What is robust hashing?

Answer 95

Maps two similar inputs to the same hash value One way error tolerant (if reading is little off, you still get same hash) easy to generate Scalability (collision free)

Question 96

What is fuzzy vaults?

Answer 96

A key-binding approach Start with a numerical secret that can be broken down to a polynomial During enrollment, minutiae from the fingerprints are plotted on the polynomial. Now the graf is just a mess of points based on the minutiae - chaf points that are hiding the polynomial During verification you take the same minutiae from the fingerprint and remove it from the graph, to get back the secret polynomial

Question 97

What is fuzzy commitment

Answer 97

Key-binding approach Have a codeword C that is encoded in binary Then you use a fixed length biometric feature vector X (fingerprint, ...) A commitment is then made by XOR-ing X with C A hash of C and the commitment is stored in the database

Question 98

What are the recognition techniques used in behavioural biometric systems?

Answer 98

Example: touch recognition Data alignment: - x- and y-coordinates for touch during different time - How is the specific fingers moving, are they crossing or just going up and down? Distance function Dissimilarity score

Question 99

What is two factor authentication?

Answer 99

When you combine two out of the three types of authentication (something you are, -have, -know)

Question 100

What are software OTPs (one time password)

Answer 100

A password is generated and sent to you (your phone etc.) Is event based - the moving factor is triggered by an event

Question 101

What is hardware OTPs?

Answer 101

You have a token that contains a number, and then you provide that number to be verified by an authentication service. Time based OTP - moving factor is time OTP is changing on the hardware token and the server at the same time interval

Question 102

What is Kerberos?

Answer 102

A protocol for authentication based on tickets. Relies on a key server, that provides third party authentication in a distributed network. The access control based on the server is used to access the computer resources in the network

Question 103

Define access control

Answer 103

A series of mechanisms that specify what a user can do, which resources they can access and what operations they can perform on the system. Restrain behaviour, use and content of a system.

Question 104

What are the three functions that access control must serve in order to be successful?

Answer 104

Identification, authentication and authorization

Question 105

What is identification?

Answer 105

Identifying a subject based on a piece of public information, such as a username. Each username or identification information should be unique and should follow a standard naming scheme. The value should be non-descriptive of the subject's role or position - people often change position and tasks over time.

Question 106

What is authentication?

Answer 106

Proving the identity of a user, by using something the subject has, is or know.

Question 107

What is authorization?

Answer 107

Determining that the proven identity of a subject has some characteristics that gives them the right to access the requested object. The access criteria can be thought of as roles or rules

Question 108

What is a reference monitor?

Answer 108

A secure, always-used and testable module that controls all access to data objects or devices. It verifies the request against a table of allowable access typesfor each process on a system. It should not be possible to bypass the reference monitor (always-used) Subject request - > Reference monitor - > Deny / Grant requets Policy - >

Question 109

What is discretionary access control (DAC)?

Answer 109

A system allows the owner of the objects to control which subjects has access to which objects. Access control is at the discretion of the owner

Question 110

What is mandatory access control (MAC)?

Answer 110

Access based on a security labeling system. Users have security clearance and objects has labels that contains data classifications. Used when classification and confidentiality is very important.