〇：Primary entry doors should have controlled access via swipe card or cryptographic locks. Secondary doors should not be secured from the inside and allowed entry. 

Data centers, server rooms, and wiring closets should be located in the core areas of the facility, near wiring distribution centers. Strict access control mechanisms and procedures should be implemented for these areas. Access control mechanisms can lock smart card readers, biometric readers, or a combination of these. These restricted areas should have only one access door, but fire code requirements typically dictate that there must be at least two doors in most data centers and server rooms. Only one door should be used for daily entry and exit and the other door should be used only in case of an emergency, i.e., if a fire breaks out in a data center or server room, the door should be locked. This second door should not be an access door, meaning people should not be able to come through this door. It should be locked, but should have a panic bar that will release the lock if it is used as an exit, pushed from the inside.

×：The primary and secondary entry doors must have control access via swipe cards or cryptographic locks.  

This is incorrect because even two entry doors should not be allowed to pass through with the identification, authentication, and authorization process. There should only be one entry point into the server room. No other door should provide an entry point, but can be used for an emergency exit. Therefore, secondary doors should be protected from the inside to prevent intrusion.

×：The primary entry door should have controlled access via a guard. Two doors should not be secured from the inside and allowed entry.

The main entry door to the server room is incorrect as it requires an identification, authentication, and authorization process to be performed. Swipe cards and cryptographic locks perform these functions. Server rooms should ideally not be directly accessible from public areas such as stairways, hallways, loading docks, elevators, and restrooms. This helps prevent foot traffic from casual passersby. Those who are by the door to the area to be secured should have a legitimate reason for being there, as opposed to those on the way to the meeting room, for example.

×：The main entry door must have controlled access via swipe card or crypto lock. Two doors must have security guards.  

Two doors should not have security guards, because it is wrong. The door should be protected from the inside simply so it cannot be used as an entry. Two-door must function as an emergency exit.

〇：The client generates a session key and encrypts it with a public key.

Transport Layer Security (TLS) uses public key cryptography to provide data encryption, server authentication, message integrity, and optionally client authentication. When a client accesses a cryptographically protected page, the web server initiates TLS and begins the process of securing subsequent communications. The server performs a three-handshake to establish a secure session. After that, client authentication with a digital certificate, as the case may be, comes in. The client then generates a session key, encrypts it with the server’s public key, and shares it. This session key is used as the symmetric key for encrypting the data to be transmitted thereafter. Thus, the correct answer is: “The client generates a session key and encrypts it with the public key.” will be

×：The server generates the session key and encrypts it with the public key.

The server does not encrypt with the public key.

×：The server generates a session key and encrypts it with the private key.

Even if encryption is performed from the server side, it can be decrypted with the public key, so it is not structurally possible.

×：The client generates a session key and encrypts it with its private key.

The client side does not have the private key.

A collision is when the hash value of two different data from one hash function is the same. Hashing is one-way cryptography, which means that the original plaintext is no longer known to be one or the other.

〇：Encryption and decryption are more efficient.

Elliptic curves are rich mathematical structures that have shown usefulness in many different types of applications. Elliptic curve cryptography (ECC) differs from other asymmetric algorithms because of its efficiency; ECC is efficient because it is computationally less expensive than other asymmetric algorithms. In most cases, the longer the key, the more bloated the computation to secure it, but ECC can provide the same level of protection with a shorter key size than RSA requires.

×：Provides digital signatures, secure key distribution, and encryption.

ECC is wrong because it is not the only asymmetric algorithm that provides digital signatures, secure key distribution, and encryption provided by other asymmetric algorithms such as RSA.

×：Calculated in finite discrete logarithms.

Wrong because Diffie-Hellman and El-Gamal compute with finite discrete logarithms.

×：Uses a large percentage of resources to perform the encryption.

Incorrect because ECC when compared to other asymmetric algorithms uses much less resources. Some devices, such as wireless devices and cell phones, have limited processing power, storage, power, and bandwidth. Resource utilization efficiency is very important for the encryption methods used in this type.

〇：Keys are generated from a master key.

To generate a composite key, a master key is created and a symmetric key (subkey) is generated. The key derivation function generates the encryption key from the secret value. The secret value can be a master key, passphrase, or password. The key derivation function (KDF) generates a key for symmetric key ciphers from a given password.

×：Session keys are generated from each other.

Session keys are generated from each other, not from the master key, which is incorrect.

×：Asymmetric ciphers are used to encrypt symmetric keys.

It is incorrect because key encryption is not even related to the key derivation function (KDF).

×：The master key is generated from the session key.

Reverse, incorrect. Session keys are generally generated from master keys.

〇：Known Plaintext Attacks

A known-plaintext attack is a situation in which a decryptor can obtain plaintext indiscriminately. A ciphertext-alone attack is a situation where a decryptor can acquire ciphertext indiscriminately. A known-plaintext attack acquires the plaintext but does not know what ciphertext it is paired with, meaning that decryption is attempted with only two random ciphertexts. In this situation, it is difficult to decrypt. Therefore, the correct answer is “known-plaintext attack.

×：Selective Plaintext Attack

A choice-plaintext attack is a situation in which the decryptor can freely choose the plaintext to acquire and obtain the ciphertext.

×：Adaptive Choice Plaintext Attack

An adaptive choice-plaintext attack is a situation in which the decryptor can freely choose which plaintext to acquire and acquire the ciphertext, and can repeat the acquisition again after seeing the result.

×：None of the above

It is rare for the answer to be “none of the above” when the choice is “most of the above.

〇：* (star) Integrity Property

The Biba model defines a model with completeness as having two axioms. The * (star) Integrity Property is that the subordinate’s document is to be seen and there is no Read Down. The * (star) Integrity Property is that there is no Write Up, that is, no rewriting of the supervisor’s document. If the Simple Integrity Axiom is not followed, the subordinate’s document will be seen and may absorb unclassified and incorrect information at a lower level. If the * (star) Integrity Property is not followed, a supervisor’s document will be rewritten, which will release incorrect information to the supervisor who sees it. Therefore, both are integrity conditions.

×：Simple Integrity Property

The Simple Integrity Property is a constraint on Read Down.

×：Strong Tranquillity Axiom

The Strong Tranquillity Axiom is the constraint not to change permissions while the system is running.

×：Weak Tranquillity Axiom

Weak Tranquillity Axiom means do not change privileges until the attribute is inconsistent.

〇：The sender encrypts the message digest with his/her private key.

A digital signature is a hash value encrypted with the sender’s private key. The act of digitally signing means encrypting the hash value of the message with his/her private key. The sender would encrypt that hash value using her private key. When the recipient receives the message, she performs a hash function on the message and generates the hash value herself. She then decrypts the hash value (digital signature) sent with the sender’s public key. The receiver compares the two values and, if they are the same, can verify that the message was not altered during transmission.

×：The sender encrypts the message digest with his/her public key.

The sender is wrong because if the message encrypts the digest with his/her public key, the recipient cannot decrypt it. The recipient needs access to the sender’s private key, which must not occur. The private key must always be kept secret.

×：The receiver encrypts the message digest with his/her private key.

The receiver is wrong because the message must decrypt the digest with the sender’s public key. The message digest is encrypted with the sender’s private key, which can only be decrypted with the sender’s public key.

×：The receiver encrypts the message digest with his/her public key.

The receiver is wrong because the message must decrypt the digest with the sender’s public key. The message digest is encrypted with the sender’s private key, which can only be decrypted with the sender’s public key.

〇：Execution Domain Switching

Execution domain switching occurs when the CPU needs to move between executing instructions for a more trusted process versus a less trusted process. Trusted Computing Base (TCB) allows processes to switch domains in a secure manner to access different levels of information based on sensitivity. Execution domain switching occurs when a process needs to invoke a process in a higher protection ring. The CPU executes the user-mode instruction back into privileged mode.

At first glance, this is a geeky problem that does not make sense. But don’t give up. Since there is no such thing as skipping, you can only get a right or wrong answer when the question is posed, so it is preferable to answer the question with some degree of prediction.

From this point on, let’s consider how to answer the questions. If you look at the question text and read it to the point where it reads, “You moved from one area to the other, and that was a security breach?” If you can read to that point, then you have two choices: deny or “stop the process,” or change or “switch the domain of execution. Next, the question text reads “if you need to access it,” which is asking how to accomplish this objective, not whether or not you should.

×：Execution of I/O operations

This is incorrect because input/output (I/O) operations are not initiated to ensure security when a process in one domain needs to access another domain in order to retrieve sensitive information. I/O operations are performed when input devices (such as a mouse or keyboard) and output devices (such as a monitor or printer, etc.) interact with an application or applications.

×：Stopping a Process

A process deactivation is one that occurs when a process instruction is fully executed by the CPU or when another process with a higher priority calls the CPU, which is incorrect. When a process is deactivated, new information about the new requesting process must be written to a register in the CPU. The TCB component must ensure that this is done, since the data replaced in the registers may be confidential.

×：Mapping from virtual memory to real memory

Incorrect because memory mapping occurs when a process needs its instructions and data processed by the CPU. The memory manager maps logical addresses to physical addresses so that the CPU knows where to place the data. This is the responsibility of the operating system’s memory manager.

〇：Conflict condition

A race condition is present when a process performs a task on a shared resource and the sequence could be in the wrong order. 2 or more processes can have a race condition if they use a shared resource, like data in a variable. It is important that processes perform their functions in the correct sequence.

×：Backdoors

Backdoors are incorrect because they are “listening” services on certain ports. Backdoors are implemented by attackers to allow easy access to the system without authenticating as a normal system user.

×：Maintenance Hooks

Maintenance hooks are specific software codes that allow easy and unauthorized access to sensitive parts of a software product. Software programmers use maintenance hooks to allow them to get quick access to the code so that they can make fixes in immediate, but this is dangerous.

×：Data validation errors

Data validation errors are wrong because an attacker cannot operate on the process execution sequence.

〇：Graham-Denning Model

The Graham-Denning model addresses how access rights between subjects and objects are defined, developed, and integrated. It defines a basic set of rights in terms of the commands that a particular subject can execute on an object. The model has eight basic protective rights or rules on how to safely perform these types of functions

×：Brewer-Nash Model

It is incorrect because its purpose is to provide access control that can be changed dynamically according to the user’s previous actions. The main purpose is to protect against conflicts of interest due to user access attempts. For example, if a large marketing firm provides marketing promotions and materials for two banks, the employee responsible for the Bank A project should not be able to see information about Bank B, the marketing firm’s other bank customer. A conflict of interest could arise because the banks are competitors. If the project manager of the marketing firm’s Project A can see information about Bank B’s new marketing campaign, he may attempt to execute it rather than promote it to please more direct customers. Marketing firms have a bad reputation when internal employees can act irresponsibly.

×：Clark-Wilson Model

The Clark-Wilson model is incorrect because it is implemented to protect data integrity and ensure that transactions are properly formatted within the application. Subjects can only access objects through authorized programs. Segregation of duties is enforced. Auditing is required. The Clark-Wilson model addresses three integrity goals: preventing changes by unauthorized users, preventing inappropriate changes by unauthorized users, and maintaining internal and external consistency.

×：Bell-LaPadula Model

This model was developed to address concerns about the security of U.S. military systems and the leakage of classified information, and is incorrect. The primary goal of the model is to prevent unauthorized access to classified information. It is a state machine model that enforces the confidentiality aspect of access control. Matrices and security levels are used to determine if a subject has access to different objects. Specific rules are applied to control how objects interact with each other compared to the subject’s object classification.

〇：Data Encryption

The Advanced Encryption Standard (AES) is a data encryption standard developed to improve upon the previous de facto standard, Data Encryption Standard (DES). As a symmetric algorithm, AES is used to encrypt data. Therefore, the correct answer is “data encryption.

There are other situations where AES is used in the other choices, but encrypting data is the most focused or better answer. Thus, there are cases where all of the choices are correct.

×：Data integrity

This is a characteristic of digital signatures.

×：Key recovery

It is a property of decryption and key escrow.

×：Symmetric key distribution

Using symmetric keys for AES distribution lowers the key delivery problem.

〇：Keys will need to be distributed via a secure transmission channel.

For two users to exchange messages encrypted with a symmetric algorithm, they need to figure out how to distribute the key first. If the key is compromised, all messages encrypted with that key can be decrypted and read by an intruder. Simply sending the key in an email message is not secure because the key is not protected and can easily be intercepted and used by an attacker.

×：Computation is more intensive than in asymmetric systems.

That is incorrect because it describes the advantages of symmetric algorithms. Symmetric algorithms tend to be very fast because they are less computationally intensive than asymmetric algorithms. They can encrypt and decrypt relatively quickly large amounts of data that take an unacceptable amount of time to encrypt and decrypt with asymmetric algorithms.

×：Much faster operation than asymmetric systems

Symmetric algorithms are faster than asymmetric systems, but this is an advantage. Therefore, it is incorrect.

×：Mathematically intensive tasks must be performed

Asymmetric algorithms are wrong because they perform a mathematically intensive task. Symmetric algorithms, on the other hand, perform relatively simple mathematical functions on bits during the encryption and decryption process.

〇：All failed access attempts should be logged and reviewed.

The physical access control system may use software and auditing capabilities to generate an audit trail or access log associated with access attempts. The date and time of the entry point when access was attempted, the user ID used when access was attempted, and any failed access attempts, among others, should be recorded.

×：Failed access attempts are recorded and only security personnel are entitled to review them.

Unless someone actually reviews them, the access logs are as useless as the audit logs generated by the computer. Security guards should review these logs, but security professionals and facility managers should review these logs on a regular basis. The administrator must know the existence and location of entry points into the facility.

×：Only successful access attempts should be logged and reviewed.

Wrong, as unsuccessful access attempts should be logged and reviewed. Audit should be able to alert you to suspicious activity even though you are denying an entity access to a network, computer, or location.

×：Failed access attempts outside of business hours should be logged and reviewed.

Incorrect, as all unauthorized access attempts should be logged and reviewed regardless. Unauthorized access can occur at any time.

The Kerckhoffs’s principle is the idea that cryptography should be secure even if everything but the private key is known. When encrypting data, one decides on a private key and how to encrypt it using that private key. Kerckhoffs says that even if it is known how it is encrypted, it should not be deciphered as long as the secret key is not discovered. Encryption has been with the history of human warfare. The main purpose is to communicate a strategy to one’s allies without being discovered by the enemy. In battle, its designs and encryption devices may be stolen by spies. Therefore, the encryption must be such that it cannot be solved without the key, no matter how much is known about how it works.

〇：TOC/TOU

Certain attacks can take advantage of the way a system processes requests and performs tasks. A TOC/TOU attack handles a series of steps that the system uses to complete a task. This type of attack takes advantage of the reliance on the timing of events occurring in a multitasking operating system; TOC/TOU is a software vulnerability that allows the use of condition checking (i.e., credential verification) and the results from that condition checking function. In the scenario in this question, the fact that the web application is likely correctly configured indicates that the programming code of this application has this type of vulnerability embedded in the code itself.

×：Buffer overflow

When too much data is accepted as input to a particular process, a buffer overflow occurs. This is incorrect because it does not match the event in the problem statement. A buffer is an allocated segment of memory. A buffer can overflow arbitrarily with too much data, but to be used by an attacker, the code inserted into the buffer must be of a specific length and require a command to be executed by the attacker. These types of attacks are usually exceptional in that the fault is segmented, or sensitive data is provided to the attacker.

×：Blind SQL Injection

Blind SQL injection attacks are wrong because they are a type of SQL injection attack that sends true or false questions to the database. In a basic SQL injection, the attacker sends specific instructions in SQL format to query the associated database. In a blind SQL attack, the attacker is limited to sending a series of true-false questions to the database in order to analyze the database responses and gather sensitive information.

×：Cross Site Request Forgery (CSRF)

Cross Site Request Forgery (CSRF) is incorrect because it is an attack type that attempts to trick the victim into loading a web page containing malicious requests or operations. The attack operation is performed within the context of the victim’s access rights. The request inherits the victim’s identity and performs undesirable functions for the victim. In this type of attack, the attacker can cause the victim’s system to perform unintended actions such as changing account information, retrieving account data, or logging out. This type of attack could be related to the scenario described in this question, but focuses on how the user can bypass the locking mechanism built into the web application. The logic in the programming code is incorrectly developed and the locking function is bypassed because a rigorous series of checks and usage sequences are not performed correctly.

Compromise is when what used to be secure encryption becomes insecure due to the evolution of computers. Cryptography is based on the sharing of a single answer, a key, among those communicating. The key is generated by computer calculations, and a third party must solve a difficult problem that would take several years to derive. However, as the computational power of computers has evolved, it is now possible to solve difficult problems that could not be solved before. In this case, encryption is meaningless. This is the compromise caused by evolution. Therefore, the correct answer is “Compromise.

〇：OCSP is a protocol developed specifically to check CRLs during the certificate validation process.

A Certificate Authority (CA) is responsible for creating certificates, maintaining and distributing them, and revoking them when necessary. Revocation is handled by the CA and the revoked certificate information is stored in a Certificate Revocation List (CRL). This is a list of all revoked certificates. This list is maintained and updated periodically. A certificate is revoked if the key owner’s private key has been compromised, if the CA has been compromised, or if the certificate is incorrect. If a certificate is revoked for any reason, the CRL is a mechanism for others to inform you of this information. The Online Certificate Status Protocol (OCSP) uses this CRL; when using CRLs, the user’s browser must examine the CRL value to the client to see if the accreditation has been revoked or the CA is constantly checking to make sure they have an updated CRL. If OCSP is implemented, it will do this automatically in the background. It performs real-time verification of the certificate and reports back to the user whether the certificate is valid, invalid, or unknown.

×：CRL was developed as a more efficient approach to OCSP.

CRLs are often incorrect because they are a cumbersome approach; OCSP is used to deal with this tediousness; OCSP does this work in the background when using CRLs; OCSP checks the CRL to see if the certificate has been revoked by Checks.

×：OCSP is a protocol for submitting revoked certificates to CRLs.

OCSP is incorrect because it does not submit revoked certificates to the CRL; the CA is responsible for certificate creation, distribution, and maintenance.

×：CRL provides real-time validation of certificates and reports to OCSP.

Incorrect because CRL does not provide real-time validation of certificates to OCSP.

〇：Crime Prevention by Environmental Design (CPTED)

Crime Prevention by Environmental Design (CPTED) is a method by which crime can be reduced through proper design of the physical environment. It provides guidance on appropriate facility construction and environmental elements and crime prevention. It is used to guide the physical environment to behavioral effects that reduce crime.

×：Multi-layered defense model  

The multi-layered defense model is incorrect because it is a hierarchical architecture of physical, logical, and administrative security controls. The concept is that if one layer fails, the asset is protected by other layers. Layers should be moved from the perimeter toward the asset and implemented.

×：Hiding by Ambiguity

Concealment by ambiguity is a technique of concealment secured by concealment of information and is incorrect. Basically, it is better not to consider something to be a true secret if it is logically reachable, even if it is not public.

×：Access Control

Access control is incorrect because it is guidance by the placement of doors, fences, lighting, and landscaping as people enter. It is an abstract concept and would not fit into a concrete definition that combines sociology.

In an asymmetric algorithm, every user must have at least one key pair (private and public key). In a public key system, each entity has a separate key. The formula for determining the number of keys needed in this environment is by the number N × 2, where N is the number of people to distribute. In other words, 260 x 2 = 520. Therefore, the correct answer is 520.