INF140 - quizer

In Linux umask is a command that determines the settings of a mask that controls how file permissions are set for newly created files. By default the umask value for a directory is 022, which results into default directory permissions are 755 and default file permissions are 644. Basically, in the 9 bits of access right (read, write, execute), they follow bitwise arithmetic below 1. directory: for each bit of permissions, the permission bit = 1 - the umask bit 2. file: for each bit of read and write permissions, the permission bit = 1 - the umask bit; the permission bit for execute is 0 Suppose for a directory, we want to control all permissions for newly create directories as rwxrwxr--. What value should we set the umask? 003 122 021 222

003

Suppose in a stream cipher, the key stream is a 8-bit string 01010011. Then a binary string 00110110 operated by this key stream gives ciphertext _________.

01100101

List the layers of TCP/IP model from top to down. ["Transport Layer", "Application Layer", "Network Layer", "Link Layer"] ["Link Layer", "Transport Layer", "Physical Layer", "Application Layer", "Network Layer"] ["Physical Layer", "Datalink Layer", "Transpor t Layer", "Application Layer", "Network Layer"] ["Application Layer", "Datalink Layer", "Physical Layer", "Network Layer"] ["Datalink Layer", "Physical Layer", "Tansport Layer", "Application Layer"]

1. Application layer 2. Transport layer 3. Network layer 4. Datalink layer 5. Physical layer

FTP is network protocol used for the transfer of files from one host to another over a TCP-based network ["IMAP", "Telnet", "SMTP", "FTP"] is a stardardized protocol for servers to send and receive mail messages ["Telnet", "POP", "HTTP", "SSH"] is a network protocol to enable secure system administration and file transfers over insecure networks

1. FTP 2. SMTP 3. SSH

Below is the output of the command ls -l /sbin in Linux system. Which of the following is incorrect? lrwxrwxrwx 1 root root 8 Sep 4 2022 /sbin -> usr/sbin 1. Normal user has no permission to run the command: cd /sbin 2. The numeric value for this file is 777 3. The file permission indicates that it belongs to a root user 4. The file sbin is actually a link, directing to the folder /usr/sbin

1. Normal user has no permission to run the command: cd /sbin

Which of the following statements about public-key cryptography (PKC) are correct? 1. PKC enables non-repudiation which cannot be offered by symmetric cryptography 2. PKC makes the key sharing more convenient than symmetric cryptography 3. PKC schemes are more secure than symmetric cryptographic schemes since PKC use longer keys 4. PKC schemes can totally replace symmetric cryptographic schemes in practice

1. PKC enables non-repudiation which cannot be offered by symmetric cryptography 2. PKC makes the key sharing more convenient than symmetric cryptography

Which of the following statements about RBAC are correct? 1. RBAC is based on the roles that users assume in a system rather than the user's identity 2. assign access rights to roles instead of individual users 3. RBAC uses one access matrix to define access rights 4. RBAC models define a role as a job function within an organization

1. RBAC is based on the roles that users assume in a system rather than the user's identity 2. assign access rights to roles instead of individual users 4. RBAC models define a role as a job function within an organization

Which of the following statements about ABAC are correct? 1. The strength of the ABAC approach is its flexibility 2. ABAC relies upon the evaluation of attributes of the subject, attributes of the object, and access control rules 3. define authorizations that express conditions on properties of both the resource and the subject 4. ABAC have many advantages over other access control models. In many computer system, current existing AC models should be replaced with ABAC model

1. The strength of the ABAC approach is its flexibility 2. ABAC relies upon the evaluation of attributes of the subject, attributes of the object, and access control rules 3. define authorizations that express conditions on properties of both the resource and the subject

A denial of service (DoS) is refers to actions ______ that the authorized use of networks, systems, or applications by exhausting resources such as central processing units (CPU), ______, _______, and disk space.

1. prevent / impair / subvert 2. memory / bandwidth 3. bandwidth / memory

In computer system a/an ["subject", "object", "access right", "asset"] is an entity capable of accessing a resource, termed a/an ["access right", "subject", "object", "entity"] , based on an access control list

1. subject 2. object

The control of accessing resource in computer system is achieved by difference access control models. Which of the following statements are correct? 1. DAC controls access based on the identity of the requestor and on access rules (authorizations) stating what requestors are (or are not) allowed to do 2. ABAC controls access based on attributes of the user, the resource to be accessed, and current environmental conditions 3. One computer system can only adopt one access control model 4. RBAC controls access based on attributes of the user, the resource to be accessed, and current environmental conditions 5. MAC controls access based on comparing security labels, indicating how critical resources are, with security clearances, indicating system entities are eligible to access certain resources

2. ABAC controls access based on attributes of the user, the resource to be accessed, and current environmental conditions 5. MAC controls access based on comparing security labels, indicating how critical resources are, with security clearances, indicating system entities are eligible to access certain resources

Which of the following statements on symmetric ciphers, cryptographic Hash functions and MAC is wrong? 1. When a cryptographic Hash function is used in combination of a block cipher, the hash output should double length of the cipher's secret for achieving same security level 2. MAC algorithms should be reversible since the receiver needs to verify the integrity of received data 3. Secure design of symmetric ciphers, Hash functions and MAC should have the "avalanche effect" 4. Sender and receiver need to use pre-shared key for using symmetric ciphers and MAC

2. MAC algorithms should be reversible since the receiver needs to verify the integrity of received data

Suppose an RSA cryptosystem has the following setting: public key: (n=p*q, e) = (2491, 5) private key: (p, q, d) = (47, 53, 957), the message of user A is encoded as m = 45 What is the ciphertext of the message m? 2318 457 18 2312

2318

Alice and Bob plan to use DH scheme to change a secret key, and they proceed with the following steps: 1. They agree on the global parameters p = 499, generator g = 7 2. Alice generates her private key prikey1 = 36 and sends Bob her public key pubkey1 = gprikey1 mod p = 440 3. Bob generates his private key prikey1 = 276 and sends Alic his public key pubkey2 = gprikey2 mod p = 351 4. Alice and Bob both calculate the shared key pubkey2prikey1 mod p, pubkey1prikey2 mod p, respectively What is the shared key between Alice and Bob in the above process? 278 444 298 345

444

Suppose Alice generates the following parameters to carry out digital signature: public key: (n=p*q, e) = (2491, 5) private key: (p, q, d) = (47, 53, 957) Alice signs a message m = 2318 with her private key and obtains the signature s. Alice sends m||s to Bob, and Bob will verify the signature s. Which of the following is a valid signature for Alice's message m? 135 39 45 28

45

Olav, a developer, will use the common practice: userID, salt, Hash(salt, password) to store users' passwords in a system. Suppose he made a careless mistake: restricting users' passwords to be composed of 8 digits. Unfortunately this mistake was detected by a determined attacker, Christoff, who has already gotten the password file in the system. Christoff has the following password entry in the file: $6$9VC0m3IIUvTpG7Y6$yKEKJPF6/H3ZPnDC6pmfDb02FMlkpat5JgEPGWIZglL4.VIckM.vz.f6hIuENVzLAH9FdewSzRksEG.7ZNBh10 He knows that hashcat is a handy tool to crack password. By the pattern of user's password: 8 digits, he manages to find the user's password with hashcat. Which of the following is the unlucky user's password? 55584013 12345678 88888888 15263748

55584013

What is the numerical representation of the permission drwxr-xr-x of a directory?

755

_______ is used to get the physical MAC address of a device associated to an IP address in a network. HTTP FTP UDP ARP

ARP

______ is a general term individual, group, organization, or government that conducts or has the intent to conduct detrimental activities against security attributes of assets in a compute system.

Adversary

Cybersecurity deals with the protection of five important security attributes, which cover different aspects of assets in the cyberspace. Which of the following refers to the property of being genuine, and being able to be verified and trusted? Availability Confidentiality Authenticity Integrity

Authenticity

Which of the following threat actions lead to disruption, which is a circumstance or event that interrupts or prevents the correct operation of system services and function Repudiation Intrusion Masquerade Misappropriation Corruption Obstruction Inference Falsification Incapacitation Exposure Interception Misuse

Corruption Obstruction Incapacitation

________ is used to assign IP address to a new device in a network. DHCP TCP HTTTP ARP

DHCP

Suppose Vigenere cipher uses a key CRYPTO. What is the ciphertext for CYBERSECURITY?

EPZTKGGTSGBHA

In order to sufficiently protect data confidentiality with block ciphers, it is important to use correct mode of operations. Otherwise, even with AES-256, we may not be able to achieve sounding security. There are different modes of operations, which enable probabilistic encryption (namely, same plaintext blocks will be encrypted to different ciphertext blocks even with a same encryption/cipher key). Which of the following does not enable probabilistic encryption? Counter Mode (CTR) Electronic Codebook (ECB) Output Feedback (OFB) Cipher Feedback (CFB) Cipher Block Chain (CBC)

Electronic Codebook (ECB)

Public cryptographic schemes relies on one-way functions True or False?

False

The only difference between a block cipher and a MAC algorithm is that the data input for a block cipher should have a fixed-length data block as its input. True or False?

False

In digital signature, it is acceptable to use MD5 since it's faster than many schemes in the SHA family. True or False?

False Collision for MD5 can be easily found, which will compromise the security of digital signature schemes.

The common practice of password storage in today's computer systems uses salted hash for storing user's password. The extra salt in such practices increases the difficulty of dictionary attack. True or False?

False Dictionary attack can be applied no matter salt is used or not.

For confidentiality, most MAC models enforce the principle of no write up and no read down. True or False?

False For secrecy, the principle of no write-down, no read-up is enforced. For data integrity, the principle of no write-up, no read-down is enforced.

Biometric information can be used for both user authentication and forensic. For high level of security, the system design should choose low false nonmatch rate, while forensic applications should choose low false match rate. True or False?

False High security requires low false match rate, and forensic requires low false nonmatch rate.

In common password storage: userID, salt, Hash(salt, pwd), the salt is used to increase the difficulty of brute-force attack on user's pwd in case the hashed password falls in a wrong hand. True or False?

False The extra salt only prevents lookup table, rainbow table attacks of which the performance relies on pre-computed tables

Digital signature scheme provides authenticity, integrity and authenticity. Therefore it should replace MAC scheme in practice. True or False?

False When non-repudiation is not required, MAC scheme should be used since it's much faster.

Which of the following threat actions lead to unauthorized disclosure, which is a circumstance or event whereby an entity gains access to data for which the entity is not authorized. Masquerade Falsification Incapacitation Inference Misappropriation Intrusion Repudiation Obstruction Exposure Corruption Misuse Interception

Inference Intrusion Exposure Interception

Which of the following threat actions lead to usurpation, which is a circumstance or event that results in control of system services or functions by an unauthorized entity Repudiation Intrusion Inference Corruption Incapacitation Exposure Falsification Interception Misuse Obstruction Masquerade Misappropriation

Intrusion Inference Exposure Interception

The Enigma machine is a cipher device developed and used in the early- to mid-20th century to protect commercial, diplomatic, and military communication. Enigma machine has many attractive features. A remarkable one is that it enables probabilistic encryption: same letters are encrypted to different letters under a same setting (regarded as a key). Open this Enigma simulatorLinks to an external site., set the machine as follows: 3 rotors with UKW-B, rotors I, II, III ring setting: I, N, F, initial position A, A, A wired connection: A-Q, E-S With this setting, what is the ciphertext of EEEEE EEEEE? GZXBA WIQJA IQKAH PGZBAC KAHPG NSXBC WQAZX HIJOP

KAHPG NSXBC

In order to achieve and maintain sounding security, organisations should follow several fundamental security design principles. For instance, as advised by the U. S. Department of Homeland Security, the following principles should be followed: Open design, Separation of privilege, Least privilege, Psychological acceptability, Layering, Isolation, Modularity, etc _____ refers to the use of multiple, overlapping protection approaches addressing the people, technology, and operational aspects of information systems. By using multiple, overlapping protection approaches, the failure or circumvention of any individual protection approach will not leave the system unprotected.

Layering

In decapsulation process of the TCP/IP model, which of the following identifier is used at the transport layer to find the correct application? Application Name Port Number MAC address IP address

Port Number

An administer needs to grant users access to different servers based on their job functions. Which Access Control model is the BEST choice to use? DAC RBAC ABAC MAC

RBAC

_______ sends packets to a known service on the intermediary with a spoofed source address of the actual target system

Reflection attack

A security attack refers to the action of certain security threat. The attack _______ refers to that an entity deceives another by falsely denying responsibility for an act? Inference Falsification Repudiation Interception Corruption

Repudiation

Which of the following threat actions lead to deception, which is a circumstance or event that may result in an authorized entity receiving false data and believing it to be true Intrusion Repudiation Masquerade Misuse Incapacitation Corruption Interception Obstruction Inference Exposure Misappropriation Falsification

Repudiation Masquerade Falsification

______ attack targets the table of TCP connections on the server

SYN spoofing

______ refers to techniques that has as its objective the impairment of the operational effectiveness of undesirable or adversarial activity, or the prevention of espionage, sabotage, theft, or unauthorized access to or use of sensitive information or information systems.

Security controls Countermeasures Security Mechnisms Security protections

______ refers to a weakness in an information system, system security procedures, internal controls, or implementation that could be exploited or triggered by a threat source.

Security vulnerability Vulnerability

In RSA cryptosystem, the public key e should be coprime to n=p*q True or False?

True

Nowadays multi-factor authentication is a common practice of user authentication. This practice follows the principle of multi-layer protection. In general it is more secure than single-factor authentication practice. Is this statement true? True or False?

True

The security of RSA cryptosystem replies on the hardness of integer factorization. True or False?

True

A secure key sharing with public key cryptography relies on the the authenticity of sender's public key. True or False?

True,

Suppose the Playfair cipher use the following encryption matrix from the keyword CRYPTO What is the ciphertext for the plaintext SECURITY?

ZKOCPGCP

Modern block ciphers typically iterate insufficiently-strong round function several times to strengthen the security of the design. For instance, the Advanced Encryption Standard (AES) iterates on the operations of 1. SubBytes 2. ShiftRows 3. MixColumns 4. AddRoundKey The SubBytes component works as substitution cipher according to a look-up 8x8 Sbox. According to the Sbox (click hereLinks to an external site.), what is the corresponding encrypted hexadecimal for the hexadecimal c6? Rett!

b4

The following password entry was generated by Windows LAN Manager (LM)Links to an external site. and NTLMLinks to an external site. where thee character set is composed of all lower-case and upper-case English letters: Tobias::43F40EDFD0B04FB2AAD3B435B51404EE:4126D649453FF99E83177A4ACEF3B74A::: Which of the following is Tobias's password? aEZfc EFarz AezYt ekEEr

ekEEr

In biometric authentication, ______ refers to the situation that samples from the same source are erroneously assessed to be from different sources. false nonmatch false match true match true nonmatch

false nonmatch

What is the ciphertext of the following plantext "the railfence cipher is a very easy cipher to break" under the rail fence cipher with key depth 3? (The space is removed in the plaintext.) teeyhahfnhrrepeekelcpieairrrieisvsctbacayo tlciyiohifeirsrecptbkeaecpeaeayhrrarnhvsee taeceayyhoahrifneihrsvrescpetbekelcpieairr tealeccpeiaeyayihrorahrifneihrsvrescpetbek

taeceayyhoahrifneihrsvrescpetbekelcpieairr

Martin works in a consultant company. Each day he needs to use his employee card and input his pin code in order to enter into the building where he works. Which of the following factors are deployed in this example for user authentication? what a user knows what a user does what a user has what a user is

what a user knows what a user has