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Data remanence is data that persists beyond noninvasive means to delete it. Though data remanence is sometimes used specifically to refer to residual data that persists on magnetic storage, remanence concerns go beyond just that of magnetic storage media. Memory may be chip based, disk based, or tape based. Sequential memory, such as tape, must sequentially read memory, beginning at offset zero, to the desired portion of memory.

Volatile memory, such as RAM, loses integrity after a power loss; nonvolatile memory such as read-only memory ROM , disk, or tape maintains integrity without power.

Real or primary memory, such as RAM, is directly accessible by the CPU and is used to hold instructions and data for currently executing processes. Secondary memory, such as disk-based memory, is not directly accessible. The data most frequently used by the CPU is stored in cache memory.

The fastest portion of the CPU cache is the register file, which contains multiple registers. Registers are small storage locations used by the CPU to store instructions and data.

The next fastest form of cache memory is Level 1 cache, located on the CPU itself. Finally, Level 2 cache is connected to but outside of the CPU. Static randomaccess memory SRAM is used for cache memory.

It loses integrity after loss of power. The capacitors used by DRAM leak charge, and so they must be continually refreshed to maintain integrity, typically every few to a few hundred milliseconds, depending on the type of DRAM. Refreshing reads and writes the bits back to memory. SRAM does not require refreshing and maintains integrity as long as power is supplied. PROM can be written to once, typically at the factory.

A programmable logic device PLD is a field-programmable device, which means it is programmed after it leaves the factory. Degaussing destroying data via a strong magnetic field, which we will discuss shortly has no effect on SSDs. While physical disks have physical blocks eg, Block 1 is on a specific physical location on a magnetic disk , blocks on SSDs are logical and are mapped to physical blocks. Also, SSDs do not overwrite blocks that contain data; the device will instead write data to an unused block and mark the previous block unallocated.

The TRIM function improves compatibility, endurance, and performance by allowing the drive to do garbage collection in the background. This collection eliminates blocks of data, such as deleted files. A sector-by-sector overwrite behaves very differently on an SSD versus a magnetic drive, and it does not reliably destroy all data.

Destruction is the best method for SSD drives that are physically damaged. Objects may be physical, such as paper files in manila folders, or electronic, such as data on a hard drive. Object reuse attacks range from nontechnical attacks, such as dumpster diving searching for information by rummaging through unsecured trash , to technical attacks, such as recovering information from unallocated blocks on a disk drive.

In both cases, data itself usually remains and can be recovered through the use of forensic tools. Common methods include writing all zeroes or writing random characters. Destructive measures include incineration, pulverizing, and shredding, as well as bathing metal components in acid.

Destroying objects is more secure than overwriting them. It may not be possible to overwrite damaged media, though data may still be recoverable. Highly sensitive data should be degaussed or destroyed, perhaps in addition to overwriting. Though this term is sometimes used in relation to overwriting of data, here shredding refers to the process of making unrecoverable any data printed on hard copy or on smaller objects, such as floppy or optical disks.

Standards, scoping, and tailoring are used to choose and customize which controls are employed. Also, the determination of controls will be dictated by whether the data is at rest or in motion. Certification considers the system, the security measures taken to protect the system, and the residual risk represented by the system. Accreditation is the data owner's acceptance of the certification and of the residual risk, which is required before the system is put into production.

PCI-DSS seeks to protect credit cards by requiring vendors who use them to take specific security precautions. Phase 1 identifies staff knowledge, assets, and threats. Phase 2 identifies vulnerabilities and evaluates safeguards. Phase 3 conducts the risk analysis and develops the risk mitigation strategy. It presents a hierarchy of requirements for a range of classifications and systems. ISO had 11 areas, focusing on specific information security controls: 1.

Policy 2. Organization of information security 3. Asset management 4. Human resources security 5. Physical and environmental security 6. Communications and operations management 7. Access control 8. Information systems acquisition, development, and maintenance 9.

Information security incident management Business continuity management There are 34 IT processes across the 4 domains. Version 5 was released in Apr. Service Design details the infrastructure and architecture required to deliver IT services. Service Transition describes taking new projects and making them operational. Service Operation covers IT operations controls. For example, an organization that does not employ wireless equipment may declare the wireless provisions of a standard are out of scope and therefore do not apply.

Tailoring is the process of customizing a standard for an organization. It begins with controls selection, continues with scoping, and finishes with the application of compensating controls. Data in motion is data that is being transferred across a network. Each form of data requires different controls for protection, which we will discuss next. These controls are recommended for all mobile devices and media containing sensitive information that may physically leave a site or security zone.

Whole-disk encryption of mobile device hard drives is recommended. Partially encrypted solutions, such as encrypted file folders or partitions, often risk exposing sensitive data stored in temporary files, unallocated space, swap space, etc. Sites using backup media should follow strict procedures for rotating media offsite. Always use a bonded and insured company for offsite media storage.

The company should employ secure vehicles and store media at a secure site. Ensure that the storage site is unlikely to be impacted by the same disaster that may strike the primary site, such as a flood, earthquake, or fire. This includes data sent over untrusted networks such as the Internet, but VPNs may also be used as an additional defense-in-depth measure on internal networks like a private corporate WAN or private circuits like T1s leased from a service provider.

We discussed the roles required to protect data, including business or mission owners, data owners, system owners, custodians, and users. An understanding of the remanence properties of volatile and nonvolatile memory and storage media are critical security concepts to master. A company outsources payroll services to a third-party company. Which of the following roles most likely applies to the third-party payroll company?

Data controller B. Data owner D. Data processor 2. Which managerial role is responsible for the actual computers that house data, including the security of hardware and software configurations? Custodian B. Data owner C. Mission owner D. System owner 3. What method destroys the integrity of magnetic media, such as tapes or disk drives, and the data they contain by exposing them to a strong magnetic field? Bit-level overwrite B.

Degaussing C. Destruction D. Shredding 4. DRAM B. SRAM D. SSD 5. What type of memory stores bits in small capacitors like small batteries? A third-party payroll company is an example of a data processor. A data owner is a management employee responsible for assuring that specific data is protected.

A system owner is responsible for the actual computers that house data, including the security of hardware and software configurations. A custodian is a nonmanager who provides hands-on protection of assets. A data owner is a manager responsible for assuring that specific data is protected. Correct answer and explanation: B. Degaussing destroys the integrity of magnetic media, such as tapes or disk drives, and the data they contain by exposing them to a strong magnetic field.

Incorrect answers and explanations: Answers A, C, and D are incorrect. A bitlevel overwrite removes data by overwriting every sector of a disk. Destruction physically destroys data; for example, via incineration. DRAM is relatively inexpensive memory that uses capacitors. EPROM may be erased with ultraviolet light. DRAM stores bits in small capacitors like small batteries.

Executive Order —National security information. OECD privacy principles. SSD garbage collection briefly explained. What is TRIM? Next comes cryptography, including core concepts of symmetric encryption, asymmetric encryption, and hash functions.

Finally, we will discuss physical security, where we will learn that safety of personnel is paramount. This is the rule that forbids a secretcleared subject from reading a top-secret object. While Bell-LaPadula, which is discussed shortly, is focused on protecting confidentiality, other models like Biba are focused on integrity.

Reading down occurs when a subject reads an object at a lower sensitivity level, such as a top-secret subject reading a secret object. There are instances when a subject has information and passes that information up to an object, which has higher sensitivity than the subject has permission to access. This is called writing up. It is focused on maintaining the confidentiality of objects. Protecting confidentiality means users at a lower security level are denied access to objects at a higher security level.

Subjects with a Secret clearance cannot access Top Secret objects, for example. For example: subjects who are logged into a Top Secret system cannot send emails to a Secret system. For every relationship between a subject and an object, there are defined upper and lower access limits implemented by the system. Subjects have a least upper bound LUB and greatest lower bound GLB of access to the objects based on their lattice position.

What if the Secret subject writes erroneous information to a Top Secret object? Integrity models such as Biba address this issue.

Biba is the model of choice when integrity protection is vital. This prevents subjects from accessing information at a lower integrity level. This protects integrity by preventing bad information from moving up from lower integrity levels. This prevents subjects from passing information up to a higher integrity level than they have clearance to change. This protects integrity by preventing bad information from moving up to higher integrity levels.

Biba is often used where integrity is more important than confidentiality. Examples include time and location-based information. Biba takes the Bell-LaPadula rules and reverses them, showing how confidentiality and integrity are often at odds.

Because the programs have specific limitations to what they can and cannot do to objects, Clark-Wilson effectively limits the capabilities of the subject. The concept of well-formed transactions provides integrity. The process is comprised of what is known as the access control triple: user, transformation procedure, and constrained data item. A matrix is a data structure that acts as a lookup table for the operating system.

The columns of the table show the access control list ACL for each object or application. The complexity of an issue, such as reading a sector from a disk drive, is contained to one layer; in this case, the hardware layer. One layer, such as the application layer, is not directly affected by a change to another. Hardware 2. Kernel and device drivers 3. Operating system OS 4. That said, computers are tremendously complex machines, and abstraction provides a way to manage that complexity.

More broadly defined, domains are groups of subjects and objects with similar security requirements. The innermost ring is the most trusted, and each successive outer ring is less trusted. Processes communicate between the rings via system calls, which allow processes to communicate with the kernel and provide a window between the rings. An open system is not the same as open source. An open system uses standard hardware and software, while open-source software makes source code publicly available.

The hardware must provide confidentiality, integrity, and availability for processes, data, and users. The motherboard contains hardware including the CPU, memory slots, firmware, and peripheral slots, such as peripheral component interconnect slots. The keyboard unit is the external keyboard. Ultimately, everything a computer does is mathematical: adding numbers, which can be extended to subtraction, multiplication, division, etc.

CPUs are rated by the number of clock cycles per second. Fetch Instruction 1 2. Decode Instruction 1 3. Execute Instruction 1 4. Write save Result 1 These four steps take one clock cycle to complete. Each part is called a pipeline stage; the pipeline depth is the number of simultaneous stages that may be completed at once. A four-stage pipeline can combine the stages of four other instructions: 1. Fetch Instruction 2, Decode Instruction 1 3. This increases the throughput. A CPU interrupt is a form of hardware interrupt that causes the CPU to stop processing its current task, save the state, and begin processing a new request.

When the new task is complete, the CPU will complete the prior task. A heavyweight process HWP is also called a task. A parent process may spawn additional child processes called threads. A thread is a lightweight process LWP. Threads are able to share memory, resulting in lower overhead compared to heavy weight processes. Multitasking allows multiple tasks heavyweight processes to run simultaneously on one CPU.

Multiprocessing has a fundamental difference from multitasking: it runs multiple processes on multiple CPUs. Virtual memory provides many functions, including multitasking multiple tasks executing at once on one CPU , swapping, and allowing multiple processes to access the same shared library in memory, among others.

It first runs the power-on self-test POST , which performs basic tests, including verifying the integrity of the BIOS itself, testing the memory, and identifying system devices, among other tasks. Once the POST process is complete and successful, it locates the boot sector for systems that boot off disks , which contains the machine code for the operating system kernel.

The kernel then loads and executes, and the operating system boots up. It is often used to support records retention for legal or regulatory compliance. WORM storage helps assure the integrity of the data it contains; there is some assurance that it has not been and cannot be altered, short of destroying the media itself. Not all computer manufacturers employ TPM chips, but the adoption has steadily increased. The TPM chip allows for hardware-based cryptographic operations.

Security functions can leverage the TPM for random number generation; the use of symmetric, asymmetric, and hashing algorithms; and secure storage of cryptographic keys and message digests. The most commonly referenced use case for the TPM chip is ensuring boot integrity.

By operating at the hardware level, the TPM chip can help ensure that kernel-mode rootkits are less likely to be able to undermine operating system security. In addition to boot integrity, TPM is also commonly associated with some implementations of full disk encryption. The two most prominent protections against this attack are data execution prevention DEP and address space location randomization ASLR. Another protection mechanism, ASLR, seeks to make exploitation more difficult by randomizing memory addresses.

For example, imagine an adversary develops a successful working exploit on his or her own test machine. When the code is run on a different system using ASLR, the addresses will change, which will probably cause the exploit to fail.

Operating systems provide memory, resource, and process management. It provides the interface between hardware and the rest of the operating system, including applications.

That boot sector contains the beginning of the software kernel machine code, which is then executed.

It enforces the system's security policy, such as preventing a normal user from writing to a restricted file, like the system password file. A Type 1 hypervisor, also called bare metal, is part of an operating system that runs directly on host hardware. A Type 2 hypervisor runs as an application on a normal operating system, such as Windows Many virtualization exploits target the hypervisor, including hypervisor-controlled resources shared between host and guests, or guest and guest.

These include cut-andpaste, shared drives, and shared network connections. As discussed previously, complexity is the enemy of security1; the sheer complexity of virtualization software may cause security problems. Combining multiple guests onto one host may also raise security issues.

Virtualization is no replacement for a firewall; never combine guests with different security requirements such as DMZ and internal onto one host. The risk of virtualization escape is called VMEscape, where an attacker exploits the host OS or a guest from another guest. Many network-based security tools, such as network intrusion detection systems, can be blinded by virtualization. A cloud also implies geographic diversity of computer resources. The goal of cloud computing is to allow large providers to leverage their economies of scale to provide computing resources to other companies that typically pay for these services based on their usage.

IaaS provides an entire virtualized operating system, which the customer configures from the OS on up. PaaS provides a preconfigured operating system and the customer configures the applications. Finally, SaaS is completely configured, from the operating system to applications, and the customer simply uses the application.

In all three cases, the cloud provider manages hardware, virtualization software, network, backups, etc. See Table 3. Private clouds house data for a single organization and may be operated by a third party or by the organization itself. Benefits of cloud computing include reduced upfront capital expenditure, reduced maintenance costs, robust levels of service, and overall operational cost savings.

From a security perspective, taking advantage of public cloud computing services requires strict service level agreements and an understanding of new sources of risk.

Organizations should also negotiate specific rights before signing a contract with a cloud computing provider. These rights include the right to audit, the right to conduct a vulnerability assessment, and the right to conduct a penetration test, both electronic and physical, of data and systems placed in the cloud.

Rather than achieving highperformance computational needs by having large clusters of similar computing resources or a single high-performance system, such as a supercomputer, grid computing attempts to harness the computational resources of a large number of dissimilar devices. One of the key security concerns with parallel systems is ensuring the maintenance of data integrity throughout the processing.

This shared memory, if not appropriately managed, can expose potential race conditions that introduce integrity challenges. Any system may act as a client, a server, or both, depending on the data needs.

Decentralized peer-to-peer networks are resilient; there are no central servers that can be taken offline. Integrity is a key P2P concern. With no central repository of data, what assurance do users have of receiving legitimate data? Cryptographic hashes are a critical control and should be used to verify the integrity of data downloaded from a P2P network.

Thin clients rely on central servers, which serve applications and store the associated data. Thin clients allow centralization of applications and their data, as well as the associated security costs of upgrades, patching, data storage, etc.

Thin clients may be hardware based such as diskless workstations or software based such as thin client applications. We will also discuss countermeasures, or mitigating actions that reduce the associated risk. The communication channel used by malware installed on a system that locates personally identifiable information PII such as credit card information and sends it to a malicious server is an example of a covert channel. Two specific types of covert channels are storage channels and timing channels.

Attackers will often install a backdoor after compromising a system. There are many types of malicious code; viruses, worms, Trojans, and logic bombs can all cause damage to targeted systems. Zero-day exploits are malicious code ie, a threat for which there is no vendor-supplied patch, meaning there is an unpatched vulnerability.

Also called multipart virus. Worms typically cause damage two ways: first by the malicious code they carry and then the loss of network availability due to aggressive self-propagation. The term derives from the Trojan horse described in Virgil's poem The Aeneid.

Kernel-mode rootkits operate in ring 0 on most operating systems. The original executable is compressed, and a small decompresser is prepended to the executable. Upon execution, the decompresser unpacks the compressed executable machine code and runs it. Packers are a neutral technology that is used to shrink the size of executables.

Many types of malware use packers, which can be used to evade signature-based malware detection. Malware such as worms often contain logic bombs, behaving in one manner, then changing tactics on a specific date and time. Signaturebased antivirus software uses static signatures of known malware.

Heuristic-based antivirus uses anomaly-based detection to attempt to identify behavioral characteristics of malware, such as altering the boot sector. Patching, system hardening, firewalls, and other forms of defense-in-depth mitigate server-side attacks.

Organizations should not allow direct access to server ports from untrusted networks such as the Internet, unless the systems are hardened and placed on DMZ networks. Client-side attacks are difficult to mitigate for organizations that allow Internet access. Clients include word processing software, spreadsheets, media players, Web browsers, etc. They often fail to prevent client-side attacks.

Unlike HTML, which provides a way to display content, applets are executables. The primary security concern is that applets are downloaded from servers, then run locally. Malicious applets may be able to compromise the security of the client. Java applets run in a sandbox, which segregates the code from the operating system.

The sandbox is designed to prevent an attacker who is able to compromise a java applet from accessing system files, such as the password file. They use digital certificates instead of a sandbox to provide security. One of their best-known projects is the OWASP Top 10 project, which provides consensus guidance on what are considered to be the 10 most significant application security risks.

In addition to the wealth of information about application security threats, vulnerabilities, and defenses, OWASP also maintains a number of security tools available for free download including a leading interception proxy called the Zed Attack Proxy ZAP. XML is used on the web, but is not tied to it; XML can be used to store application configuration and output from auditing tools, among other things.

Extensible means users may use XML to define their own data formats. SOA is intended to allow multiple heterogeneous applications to be consumers of services. The service can be used and reused throughout an organization rather than built within each individual application that needs the functionality offered by the service. Services are expected to be platform independent and able to be called in a generic way that is also independent of a particular programming language.

The intent is that that any application may leverage the service simply by using standard means available within their programming language of choice.

Services are typically published in some form of a directory that provides details about how the service can be used and what the service provides.

Though web services are not the only example, they are the most common example provided for the SOA model. The sheer amount of data that may be housed in a database requires special security consideration. The word polyinstantiation is based on the Latin roots for multiple poly and instances instantiation.

Database polyinstantiation means two rows may have the same primary key, but different data. These issues occur in multiple realms, including database security.

Inference requires deduction. There is a mystery to be solved, and lower level details provide the clues. Aggregation is a mathematical process; a user asks every question, receives every answer, and derives restricted information. Traditional network-based protection, such as firewalls and intrusion detection systems, are powerless to prevent the initial attack.

Technical controls to mitigate infected mobile computers include requiring authentication at OSI model Layer 2 via Another mobile device security concern is the loss or theft of a mobile device, which threatens the confidentiality, integrity, and availability of the device and the data that resides on it.

Backups can assure the availability and integrity of mobile data. Full disk encryption also known as whole disk encryption ensures the confidentiality of mobile device data. Remote wipe capability is another critical control, which describes the ability to erase and sometimes disable a mobile device that is lost or stolen. While it may be known that the data is being transmitted, the content of that data should remain unknown to third parties.

Data in motion moving on a network and data at rest stored on a device, such as a disk may be encrypted for security. Cryptography creates messages with hidden meaning; cryptanalysis is the science of breaking those encrypted messages to recover their meaning. Many use the term cryptography in place of cryptology; however, it is important to remember that cryptology encompasses both cryptography and cryptanalysis.

A cipher is a cryptographic algorithm. A plaintext is an unencrypted message. Encryption converts a plaintext to a ciphertext. Decryption turns a ciphertext back into a plaintext. It is important to note that it does not directly provide availability. Cryptography can also provide authentication, which proves an identity claim. Additionally, cryptography can provide nonrepudiation, which is an assurance that a specific user performed a specific transaction that did not change. Confusion means that the relationship between the plaintext and ciphertext should be as confused or random as possible.

Cryptographic substitution replaces one character for another; this provides the confusion. Permutation, also called transposition, provides diffusion by rearranging the characters of the plaintext, anagram-style. Strong encryption destroys patterns. Any signs of nonrandomness can be clues for a cryptanalyst, hinting at the underlying order of the original plaintext or key.

For key-based encryption, it should be very difficult ideally, impossible to convert a ciphertext back to a plaintext without the key. The work factor describes how long it will take to break a cryptosystem decrypt a ciphertext without the key. Secrecy of the cryptographic algorithm does not provide strength; in fact, secret algorithms are often proven quite weak. Strong crypto relies on math, not secrecy, to provide strength.

A polyalphabetic cipher uses multiple alphabets; for example, E substitutes for X one round, then S the next round. Polyalphabetic ciphers attempt to address this issue via the use of multiple alphabets. Combining a key with a plaintext via XOR creates a ciphertext. XORing the same key to the ciphertext restores the original plaintext.

XOR math is fast and simple, so simple that it can be implemented with phone relay switches. Two bits are true or 1 if one or the other exclusively, not both is 1. In other words: if two bits are different, the answer is 1 true.

If two bits are the same, the answer is 0 false. XOR uses a truth table, shown in Table 3. This dictates how to combine the bits of a key and plaintext. Full disk encryption also called whole disk encryption of a magnetic disk drive using software such as BitLocker or PGP Whole Disk Encryption is an example of encrypting data at rest.

For example, as we will learn later this chapter, a digital signature provides authentication and integrity, but not confidentiality. Symmetric ciphers are primarily used for confidentiality, and AES is preferable over DES due to its strength and performance. Symmetric cryptography uses a single key to encrypt and decrypt. Asymmetric cryptography uses two keys, one to encrypt and the other to decrypt. Hashing is a one-way cryptographic transformation using an algorithm, but no key.

Table 3. If you encrypt a zip file, then decrypt with the same key, you are using symmetric encryption. Strengths of this method include speed and cryptographic strength per bit of key; however, the major weakness is that the key must be securely shared before two parties may communicate securely.

Some block ciphers can emulate stream ciphers by setting the block size to 1 bit; they are still considered block ciphers. This ensures that identical plaintexts encrypt to different ciphertexts. Chaining called feedback in stream modes seeds the previous encrypted block into the next block ready for encryption.

This destroys patterns in the resulting ciphertext. DES Electronic Code Book mode see below does not use an initialization vector or chaining, and patterns can be clearly visible in the resulting ciphertext. IBM designed DES, based on their older Lucifer symmetric cipher, which uses a bit block size ie, it encrypts 64 bits each round and a bit key. It may sound like splitting hairs, but that is an important distinction to keep in mind on the exam.

DEA may be the best answer for a question regarding the algorithm itself. It uses no initialization vector or chaining. Identical plaintexts with identical keys encrypt to identical ciphertexts. Two plaintexts with partial identical portions, such as the header of a letter, encrypted with the same key will have partial identical ciphertext portions.

The first encrypted block is an initialization vector that contains random data. One limitation of the CBC mode is that encryption errors will propagate; an encryption error in one block will cascade through subsequent blocks due to the chaining, therefore destroying their integrity.

It uses feedback, which is the name for chaining when used in stream modes, to destroy patterns. CFB uses the previous ciphertext for feedback. The previous ciphertext is the subkey XORed to the plaintext. Since the subkey is not affected by encryption errors, errors will not propagate. CTR mode uses a counter, so this mode shares the same advantages as OFB in that patterns are destroyed and errors do not propagate.

However, there is an additional advantage: since the feedback can be as simple as an ascending number, CTR mode encryption can be executed in parallel. The work factor required to break DES was reasonable in , but advances in CPU speed and parallel architecture have made DES weak to a brute-force key attack today, where every possible key is generated and attempted.

It uses a bit key and bit block size. The IDEA has patents in many countries. AES uses bit with 10 rounds of encryption , bit with 12 rounds of encryption , or bit with 14 rounds of encryption keys to encrypt bit blocks of data. Fifteen AES candidates were announced in August , and the list was reduced to five in August Rijndael was chosen and became AES.

Blowfish uses from through bit keys the default is bit to encrypt 64 bits of data. Both are open algorithms, meaning they are unpatented and freely available. RC5 uses bit testing purposes , bit replacement for DES , or bit blocks. The key size ranges from zero to bits. RC6 was an AES finalist. It is also stronger than RC5, encrypting bit blocks using , , or bit keys. The public key, as its name indicates, is made public, and asymmetric encryption is also called public key encryption for this reason.

Anyone who wants to communicate with you may simply download your posted public key and use it to encrypt their plaintext. Once encrypted, your public key cannot decrypt the plaintext, but your private key can do so.

As the name implies, your private key must be kept private and secure. Additionally, any message encrypted with the private key may be decrypted with the public key, as it is for digital signatures, as we will see shortly.

These methods use one-way functions, which are easy to compute one way but are difficult to compute in the reverse direction. Multiplying the prime number by the prime number results in the composite number 49,, That way is quite easy to compute, as it takes just milliseconds on a calculator. Factoring is the basis of the RSA algorithm. Computing 7 to the 13th power exponentiation is easy on a modern calculator: 96,,, Discrete logarithms apply logarithms to groups, which is a much harder problem to solve.

This one-way function is the basis of the Diffie-Hellman and ElGamal asymmetric algorithms. An attacker who is able to sniff the entire conversation is unable to derive the exchanged key. Diffie-Hellman uses discrete logarithms to provide security. Solving this problem is harder than solving discrete logarithms, so algorithms based on elliptic curve cryptography ECC are much stronger per bit than systems using discrete logarithms and also stronger than factoring prime numbers.

ECC requires less computational resources because it uses shorter keys comparison to other asymmetric methods. Lower-power devices often use ECC for this reason.

The strength of asymmetric encryption is the ability to communicate securely without presharing a key. They are called one-way hash functions because there is no way to reverse the encryption.

Common older hash functions include secure hash algorithm 1 SHA-1 , which creates a bit hash and Message Digest 5 MD5 , which creates a bit hash. Assume you are hashing documents that are a megabit long with MD5. Think of the documents as strings that are 1,, bits long, and think of the MD5 hash as a string bits long.

The universe of potential 1,,bit strings is clearly larger than the universe of bit strings. It is the most widely used of the MD family of hash algorithms. MD5 creates a bit hash value based on any input length. MD5 has been quite popular over the years, but there are weaknesses where collisions can be found in a more practical amount of time. MD6 is the newest version of the MD family of hash algorithms, first published in SHA-1 creates a bit hash value.

This is what law enforcement officials typically do when tracking a suspect who used cryptography; they obtain a search warrant and attempt to recover the key. Given enough time, the plaintext will be recovered. This technique may recover a key by tricking the key holder into revealing the key.

You may be wondering why you would need the key if you already have the plaintext, but recovering the key would allow you to also decrypt other ciphertexts encrypted with the same key. Encrypting without knowing the key is accomplished via an encryption oracle, or a device that encrypts without revealing the key.

Adaptive-chosen plaintext begins with a chosen plaintext attack in the first round. Adaptive-chosen ciphertext also mirrors its plaintext cousin: it begins with a chosen ciphertext attack in the first round. The cryptanalyst then adapts further rounds of decryption based on the previous round.

Known key means the cryptanalyst knows something about the key and can use that knowledge to reduce the efforts used to attack it. If the cryptanalyst knows that the key is an uppercase letter and a number only, other characters can be omitted in the attack. The plaintexts may differ by a few bits. The pairs are studied to derive information about the key used to create them. Both differential and linear analysis can be combined as differential linear analysis.

This means the sender cannot later deny or repudiate signing the document. Roy wants to send a digitally signed email to Rick.

Roy writes the email, which is the plaintext. He then uses the SHA-1 hash function to generate a hash value of the plaintext. He then creates the digital signature by encrypting the hash with his RSA private key. Roy then attaches the signature to his plaintext email and hits send. Attack ships on fire off the shoulder of Orion. Roy must have sent the email only Roy knows his private key.

This authenticates Roy as the sender. The email did not change. This proves the integrity of the email. If the hashes match, Roy cannot later deny having signed the email. This is nonrepudiation. If the hashes do not match, Rick knows either Roy did not send it, or that the email's integrity was violated. A digital certificate is a public key signed with a digital signature.

Digital certificates may be server-based or client-based. If client and server certificates are used together, they provide mutual authentication and encryption. The standard digital certificate format is X.

Organizational registration authorities ORAs authenticate the identity of a certificate holder before issuing a certificate to them. A certificate may be revoked if the private key has been stolen, an employee is terminated, etc. A CRL is a flat file and does not scale well. Users may lose their private key as easily as they may forget their password. A lost private key means that anything encrypted with the matching public key will be lost, short of cryptanalysis, as described previously.

Note that key storage is different than key escrow. Key escrow means a copy is retained by a third-party organization and sometimes multiple organizations , often for law enforcement purposes. A retired key may not be used for new transactions, but one may be used to decrypt previously encrypted plaintexts. A destroyed key no longer exists and therefore cannot be used for any purpose.

SSL authenticates and provides confidentiality to web traffic. SSL was developed for the Netscape Web browser in the s. SSL 2. TLS is very similar to that version, with some security improvements. AH and ESP provide different and sometimes overlapping functionality. AH provides no confidentiality; it acts as a digital signature for the data.

AH also protects against replay attacks, where data is sniffed off a network and resent, often in an attempt to fraudulently reuse encrypted authentication credentials. ESP primarily provides confidentiality by encrypting packet data. A unique bit number called the security parameter index SPI identifies each simplex SA connection. Security gateways use tunnel mode because they can provide point-to-point IPsec tunnels.

ESP tunnel mode encrypts the entire packet, including the original packet headers. The IKE negotiates the algorithm selection process. PGP provides the modern suite of cryptography: confidentiality, integrity, authentication, and nonrepudiation.

PGP can encrypt emails, documents, or an entire disk drive. PGP uses a web of trust model to authenticate digital certificates, instead of relying on a central CA. The private key is often divided into two or more parts, each held in escrow by different trusted third-party organizations, which will only release their portion of the key with proper authorization, such as a court order. This provides separation of duties. Buildings, like networks, should employ defense in depth.

Any one defense can fail, so critical assets should be protected by multiple physical security controls, such as fences, doors, walls, locks, etc. The ideal perimeter defense is safe, prevents unauthorized ingress, and offers both authentication and accountability, when applicable. Fences should be designed to steer ingress and egress to controlled points, such as exterior doors and gates. A light that allows a guard to see an intruder is acting as a detective control. Types of lights include Fresnel lights, named after Augustine-Jean Fresnel.

These are the same type of lights originally used in lighthouses, which used Fresnel lenses to aim light in a specific direction. Light measurement terms include lumen, which is the amount of light one candle creates. Lux, based on the metric system, is more commonly used now; one lux is one lumen per square meter.

CCTVs using the normal light spectrum require sufficient visibility to illuminate the field of view that is visible to the camera. Modern cameras use charge-coupled discharge CCD , which is digital. Cameras have mechanical irises that act as human irises, controlling the amount of light that enters the lens by changing the size of the aperture.

Key issues include depth of field, which is the area that is in focus, and field of view, which is the entire area viewed by the camera.

More light allows a larger depth of field because a smaller aperture places more of the image in focus. Correspondingly, a wide aperture used in lower light conditions lowers the depth of field. Locks may be mechanical, such as key locks or combination locks, while electronic locks are often used with smart cards or magnetic stripe cards.

Keys are shared or sometimes copied, which lowers the accountability of key locks. A common type is the pin tumbler lock, which has driver pins and key pins. The correct key makes the pins line up with the shear line, allowing the lock tumbler plug to turn. Ward or warded locks must turn a key through channels, or wards. A skeleton key can open varieties of warded locks. Button or keypad locks also use numeric combinations. Limited accountability due to shared combinations is the primary security issue concerning these types of locks.

A magnetic stripe card contains a magnetic stripe that stores information. Unlike smart cards, magnetic stripe cards are passive devices that contain no circuits. These cards are sometimes called swipe cards because they are read when swiped through a card reader. Policy should forbid employees from allowing tailgating and security awareness efforts should describe this risk. The first door must close and lock before the second door may be opened. Without authentication, the intruder is trapped between the doors after entering the mantrap.

Secure data centers often use floor-to-ceiling turnstiles with interlocking blades to prevent an attacker from going over or under the turnstile. Secure revolving doors perform the same function. These checks often detect metals, weapons, or explosives. Contraband checks are casually thought to be detective controls, but their presence makes them a viable deterrent to actual threats.

The echo will return more quickly when a new object, such as a person walking in range of the sensor, reflects the wave. A photoelectric motion sensor sends a beam of light across a monitored space to a photoelectric sensor. The sensor alerts when the light beam is broken. Ultrasonic, microwave, and infrared motion sensors are active sensors, which means they actively send energy. Consider a passive sensor as a read-only device; an example is a passive infrared PIR sensor, which detects infrared energy created by body heat.

All should be equally strong from a defensive standpoint, as attackers will target the weakest spot. Egress must be unimpeded in case of emergency, so a simple push button or motion detectors are frequently used to allow egress. Outward-facing emergency doors should be marked for emergency use only and equipped with panic bars, which will trigger an alarm when used. Glass windows are structurally weak and can be dangerous when shattered.

Bullet-proof or explosive-resistant glass can be used for secured areas. These are called slab-to-slab walls. Raised floors and drop ceilings can obscure where the walls truly start and stop. An attacker should not be able to crawl under a wall that stops at the top of the raised floor, or climb over a wall that stops at the drop ceiling.

Guards can inspect access credentials, monitor CCTVs and environmental controls, respond to incidents, and act as a general deterrent. All things being equal, criminals are more likely to target an unguarded building over a guarded building. The term pseudo guard means an unarmed security guard.

The primary drawback to using dogs as a perimeter control is the legal liability. In a similar way, site selection is the greenfield process of choosing a site to construct a building or data center. Electrical outages are among the most common of all failures and disasters. Generators provide longer protection but require refueling in order to operate for extended periods. The primary issue is employee safety; all employees have the right to a safe working environment. Additional issues include theft of company assets.

Will the site be externally marked as a data center? Is there shared tenancy in the building? Where is the telecom demarcation point, or telecom demark? A modest building design might be an effective way to avoid attention. Adjacent buildings pose a similar risk. Attackers can enter a less secure adjacent building and use that as a base to attack an adjacent building, often breaking in through a shared wall.

Most buildings have one demarc area where all external circuits enter the building. Access to the demarc allows attacks on the confidentiality, integrity, and availability of all circuits and the data flowing over them. An off-site media storage facility will ensure that the data is accessible even after a physical disaster at the primary facility.

The purpose of the media being stored offsite is to ensure continued access, which means the facility should be far enough removed from the primary facility to avoid the likelihood of a physical disaster affecting both the primary facility and the offsite storage location.

Licensed and bonded couriers should transfer the media to and from the offsite storage facility. These defenses assume that an attacker has physical access to the device or media containing sensitive information. In some cases, other controls may have failed and these controls are the final phase in data protection.

You cannot protect your data unless you know where and what it is. Detailed asset tracking databases support regulatory compliance by identifying where all regulated data is within a system. In case of employee termination, the asset database will show the exact equipment and data that the employee must return to the company. Completely updated for the most current version of the exam s Common Body of KnowledgeProvides the only guide you need for last-minute studyingAnswers the toughest questions and highlights core topicsStreamlined for maximum efficiency of study, making it ideal for professionals updating their certification or for those taking the test for the first time".

With over , professionals certified worldwide, and many more joining their ranks, this new third edition presents everything a reader needs to know on the newest version of the exam's Common Body of Knowledge. The eight domains are covered completely and as concisely as possible, allowing users to ace the exam. Each domain has its own chapter that includes a specially-designed pedagogy to help users pass the exam, including clearly-stated exam objectives, unique terms and definitions, exam warnings, "learning by example" modules, hands-on exercises, and chapter ending questions.

Provides the most complete and effective study guide to prepare users for passing the CISSP exam, giving them exactly what they need to pass the test Authored by Eric Conrad who has prepared hundreds of professionals for passing the CISSP exam through SANS, a popular and well-known organization for information security professionals Covers all of the new information in the Common Body of Knowledge updated in January , and also provides two exams, tiered end-of-chapter questions for a gradual learning curve, and a complete self-test appendix.

The book's 14 chapters provide in-depth discussions of the following topics: systems security; operating system hardening; application security; virtualization technologies; network security; wireless networks; network access; network authentication; risk assessment and risk mitigation; general cryptographic concepts; public key infrastructure; redundancy planning; environmental controls and implementing disaster recovery and incident response procedures; and legislation and organizational policies.

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Written by leading experts in information security certification and training, this completely up-to-date self-study system helps you pass the exam with ease and also serves as an essential on-the-job reference. The only official, comprehensive reference guide to the CISSP All new for and beyond, this is the authoritative common body of knowledge CBK from ISC 2 for information security professionals charged with designing, engineering, implementing, and managing the overall information security program to protect organizations from increasingly sophisticated attacks.

Written by a team of subject matter experts, this comprehensive reference covers all of the more than CISSP objectives and sub-objectives in a structured format with: Common and good practices for each objective Common vocabulary and definitions References to widely accepted computing standards Highlights of successful approaches through case studies Whether you've earned your CISSP credential or are looking for a valuable resource to help advance your security career, this comprehensive guide offers everything you need to apply the knowledge of the most recognized body of influence in information security.

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Using 25 CISSP practice questions with detailed explanations, this book will attempt to answer how to think like a member of a senior management team who has the goal of balancing risk, cost, and most of all, human life. The questions will take you through how to resist thinking from a technical perspective to one that is more holistic of the entire organization.