COS 330 Exam PDF

Data confidentiality: private information not available to...

Data confidentiality: private information not available to unauthorised users Confidentiality: Privacy: Assures individuals control what info related to them, may be collected and stored and by whom that info may be disclosed. Data integrity: Assures info and programs only changed in authorised manner. System integrity: System Integrity: performs intended function in an unimpaired manner. 1.1 What is meant by the CIA (Example: no external program triad? is changing the data you are currently working with) Prompt, services are available Availability: to authorised users The property is genuine, and is able to be verified and trusted, must be confident it the Authenticity: contents validity (example. CIA is well established but 2 verifying that users are who others are needed for a more they say they are) complete picture If something is to go wrong, you need to be able to point out the Accountability: point of failure. Since there are no truly perfect systems this helps to improve systems. Data integrity ensures that only a valid system or user is able to change the contents of the data (example: if you have a list of names, only authorised users can change it) 1.2 What is the difference Where system integrity focusing between data integrity and more on the actually process of system integrity? system and how it runs (example: you have a server running, if people spam your server with tons of invalid requests this will slow the system down from being able to process valid request, aka DDoS) Threat action(attack) Exposure: data released to unauthorised entity. Interception: Unauthorised entity directly access sensitive information travelling between entities. Threat Consequence - Unauthorised disclosure: A An example of inference is known as traffic analysis, in where an entity gains access to which an adversary is able to gain information from data to which it is not observing the pattern of traffic on a network, such as the authorised amount of traffic between particular pairs of hosts on the Inference: network. Another example is the inference of detailed information from a database by a user who has only limited access; this is accomplished by repeated queries whose combined results enable inference. Intrusion: gains access by circumventing system security. Threat action(attack) Masquerade: unauthorised 1.3 List and briefly define the entity pretending to be kinds of threat consequences Threat Consequence - authorised and the types of threat actions Deception: an entity receiving which cause these false data and believing it is Falsification: False data deceive consequences. true. an authorised entity Repudiation: deceives another by denying responsibility for an act Threat action(attack) Incapacitation: disabling a Threat Consequence - system component Disruption: Event that interrupts Corruption: changing the or prevents the correct systems functions or data operation of a system. Obstruction: interrupts delivery of system services by hindering system operation Threat action(attack) Misappropriation: Assumes Threat Consequence unauthorised logical or physical -Usurpation: The control of control of a system system services by an Misuse: Cause a system unauthorised entity. component to perform a function or service that is detrimental to a system. Economy of mechanism: the security measures for both hardware and software should be as simple as possible. Fail-safe default: based on permission rather than exclusion: rather of a listen of who can access the system instead of who cant. Complete mediation: Access decisions must be checked against the access system, and not rely on a cache. Which means for example don’t trust the information in a file is valid rather test it before using it. Open design: security mechanisms should be open rather than secret. Eg encryption key should be secret but the algorithm should be public. This allows for the view of the system by experts. Separation of privilege: multiple attributes needed to access a system e.g. multi factor authentication. Least privilege: Every user or process should operate with the least amount of access possible to perform the task. 1.4 List and briefly define the Least common mechanism: fundamental security design minimise the functions shared principles. by different users… Psychological acceptability: Security mechanism should not interfere unduly with the work of users. And at the same time meet the security standards (people might turn of security is it hinders usage). Isolation: separating information (keep important info away from public info) Encapsulation: is a form of isolation, also for example how functions only belong to that class and my have private and public variables. Modularity: The security should be separated into separate protected modules, this allows from more plug and use functionality and prevents from modules interfering with one another. Layering: Applying security in multiple places to ensure continuous safety. I think this Chapter 1 Overview still applies to using multiple forms of security for example 2 step verification. Least astonishment: Must always respond in a way that is least likely to astonish the user. A security policy is an informal description of desired desired system behaviour, may reference requirements for security, integrity and availability. A formal statement of rules and practises that specify or regulate how a system or organisation provides security to protect sensitive and critical resources. value of the asset being protected Things to consider when Vulnerabilities of the system developing a security policy: Potential threats and likelihood of attacks 1.5 What is a security policy? What are the actions involved Ease of use vs security: when implementing a security Trade offs to consider Cost of security versus cost of policy? failure and recovery Prevention: If you don't want people to read your data encrypting it would be a way to prevent someone from being able to read it. Detection:If you cant prevent you would then need a way to Security implementation determine who is the attacker. Response: The system may respond to to prevent the attack once it is detected. Example just shutting the system down. Recovery:The use of backup system Attack surfaces: is a reachable and exploitable vulnerability of the system: open ports on outward facing servers, the code listening to the port Services inside the firewall E.g. Code that processes incoming data interfaces , sql and web forms Employee with sensitive information Network attack surfaces: are vulnerabilities of a network, wide area network, internet. Network protocol 1.6 Differentiate between a vulnerabilities. network attack surface and a software attack surface. Software attack surfaces: Types of attack surfaces: vulnerabilities in application, utility or operating system code. Human attack surface: vulnerabilities created by personal or outside. E.g. human error and trusted insiders. Confidentiality is important for student records because students will most likely prefer Confidentiality to keep their marks private. Freely available marks could effect their ability to be hired. Lack of integrity in marks would defeat the whole point of being graded due to the fact that the marks would not be accurate. Integrity Data integrity = user file security A) How does Integrity of service differ from System integrity = system file availability? security Availability = system uptime Availability is important because without being able to access their marks, students would be Availability unable to gauge how they are doing throughout the semester, or see whether they have passed or not. Someone other than yourself Confidentiality publishes your marks online, in a public forum Someone gains access to the Integrity University student records and B) changes their marks A DDoS attack overwhelms the University servers and Availability subsequently makes it difficult for student to check their marks Patients will likely want to keep their medical history private and not in the public domain. Some Confidentiality reasons for this may be personal privacy (avoiding embossment) and/or practical reasons (insurance, work etc) Patients’ lives are quite literally at risk if they receive incorrect Questions information. For example, a patient who is diagnosed with Integrity HIV/Aids but never learns this due to a fault in the system will likely die, and infect others before they do so. If a patient does not receive their diagnosis within a timely Availability fashion it may be ‘too little too late’ and they may not receive the correct treatment in time. An unauthorised person may gain access to a patients Confidentiality private medical information and post it on a public forum An attacker could gain access to the hospitals medical records Integrity and modify a patients’ diagnosis, resulting in them being misdiagnosed An attacker could use a DDoS attack to overwhelm the hospitals servers and make it difficult for medical staff to Availability query a patients record, thus blocking staff from learning critical history information about a patient Publish proprietary corporate material A) We don’t want the next iPhone being leaked in our press release about Stores Publish laws and regulations A law firm B) We don’t want laws being altered A daily newspaper C) We don’t want the system crashing and preventing us from printing Cryptanalysis attacks rely on understanding the nature of the algorithm, plus some general knowledge of the plaintext or even some sample code. If an attack is successful the algorithm can be used to successfully read all further uses of the algorithm. This is basically what Alan Turing did with the Nazi encryption algorithm Engima. Brute-force attacks on the other hand try every possible key on a piece of ciphertext until a solution into plaintext is achieved. On average half of all 2.1 How is cryptanalysis possible keys must be tried to different from brute-force achieve success. Short attack? passwords are susceptible to brute force attacks because of this, whereas longer passwords become exponentially more difficult to break as they grow longer. Symmetric block encryption, this basically means that every character has another cipher File encryption version of itself. WE encrypt Email A symmetric encryption uses a blocks of text at a time. Applied secret key that is shared to large groups of text data. between two parties. There are two versions of this: Symmetric stream encryption, Whatsapp produces output one character at a time. Better performance + Voice chat less code. Typically used on small amounts of text. Stream of data DES, can be brute forced due to low key size 56 with ±hour search. Poor performance. Most studied encryption Firstly, what is a symmetric algorithm in history, so there is encryption scheme? the possibility to exploit its 2.2 List and briefly explain the characteristics through different approaches to cryptanalysis. attacking a symmetric encryption scheme. Triple DES, solves the brute force issue by repeating the There are three types of DES algorithm three times. symmetric block encryption: However DES is slow and Triple DES compounds this. It’s encryption is great, but performance makes it less attractive. AES, improved on both of the above with better performance and 128, 192 and 256 block lengths. Was the result of a competition. So, now that we know all of this, we can use Brute force or Cryptanalysis, however it depends on the implementation (DES, Triple DES, AES). We need a strong encryption algorithm. A would be opponent should not be able to decrypt it even if they know the 2.3 What are the two principal algorithm and possess seme requirements for the secure use cipher text. of symmetric encryption? The sender and receiver must each have obtained copies of the secret key in a secure manner. Protection against passive Eavesdropping attack 2.4 List the two important aspects of data authentication. Deleting of data Protection against active attack Modifying of data Hash the message Append a Message Symmetric Authentication Code Use secret key to encrypt Append to message and send 2.5 What is one-way hash There are three techniques for Each user has a private keys, function? hash functions: and a public key. Users can Public key, (uses two separate share data to them via their keys) unique public key and only they can open with the associated private key Secret value, Hash + (Key + Secret key is incorporated into Message) the hash process Plaintext is inserted into MAC algorithm to generate a unique key. This is then appended to the end of the plaintext and sent along with it. This is basically to be able to tell us when data has been tampered 2.6 Briefly describe the three with. schemes illustrated in Figure 2.3. Can be applied to a block of data of any size Fixed length output 2.7 What properties must a Relatively easy to compute hash function have to be useful for message authentication? One-Way You must always get the same value after the hash Can’t have duplicates Plain text Encryption algorithm 2.8 What are the principal ingredients of a public-key Public and private key cryptosystem? Ciphertext Decryption algorithm Create a hash of the message, h Digital signature // to determine Run h through a digital whether a message is valid or signature generation algorithm not with your private key, S Append this to the original message. Digital envelopes use the recipient’s public key to create a one-way sealed message. 2.9 List and briefly define three First you encrypt the message uses of a public-key with a random symmetric key cryptosystem. Then encrypt the random How do we send a secret key in symmetric key with a user’s Symmetric key distribution Chapter 2 Cryptographic a secure way? public key Tools And include this encrypted key along with the message. So the The user will use then use their “envelope” has two contents: private key to obtain the The random symmetric key random symmetric key and encrypted message, and public then unlock the message. key random symmetric key. Encryption of secret keys // means what it says The principal attraction of ECC 2.10 What advantage might compared to RSA is that it elliptic curve cryptography appears to offer equal security (ECC) have over RSA? for a far smaller bit size, thereby reducing processing overhead The digital signature does not provide confidentiality. That is, the message being sent is safe from alteration, but not safe from eavesdropping. This is obvious in the case of a signature based on a portion of 2.11 Do digital signatures the message, because the rest provide confidentiality? of the message is transmitted in the clear. Even in the case of complete encryption, there is no protection of confidentiality because any observer can decrypt the message by using the sender’s public key. A public-key certificate consists of a public key plus a user ID of the key owner, with the whole block signed by a trusted third party. The certificate also includes some information about the third party plus an indication of the period of validity of the certificate. User software (client) creates a pair of keys: one public and one private. Client prepares an unsigned certificate that includes the user ID and user’s public key. User provides the unsigned certificate to a CA in some secure manner. This might require a face-to-face meeting, the use of registered e-mail, or happen via a Web form with e- mail verification. CA uses a hash function to calculate the hash code of the unsigned certificate. A hash 2.12 What is a public-key function is one that maps a certificate? variable-length data block or message into a fixed-length CA creates a signature as value called a hash code, such follows: as SHA family that we will discuss in Sections 2.2 and 21.1. CA generates digital signature using the CA’s private key and a signature generation algorithm. CA attaches the signature to the unsigned certificate to create a signed certificate. CA returns the signed certificate to client. Client may provide the signed certificate to any other user. User calculates the hash code of certificate (not including signature). Any user may verify that the User verifies digital signature certificate is valid as follows: using CA’s public key and the signature verification algorithm. The algorithm returns a result of either signature valid or invalid. Generation of keys for public- key algorithms. Generation of a stream key for symmetric stream cipher. (a key is input to a pseudorandom bit generator that produces a stream of 8-bit numbers that are apparently random. A pseudorandom stream is one that is unpredictable without 2.13 What are three different knowledge of the input key and ways in which random numbers which has an apparently are used in cryptography? random character (see Section 2.5). The output of the generator, called a keystream, is combined one byte at a time with the plaintext stream using the bitwise exclusive-OR (XOR) operation.) Generation of a symmetric key for use as a temporary session key or in creating a digital envelope. Public key encryption Digital signatures (DS) Uses Public/Private keys to identify the creator of a file Key terms Message A user will encrypt a message Authentication Codes in combination with a secret key (MAC) using the MAC algorithm MAC would see that the MAC number is different once running the plain text through A) Both MAC and DS would the MAC algorithm determine that the message has been changed DS would see that the public key does not match the private key that the message has been encoded with B) Neither MAC nor DS are able to detect Replay requests. This can be remedied by the use of timestamp within messages DS, by using the public key of Questions the real sender Bob will see who the message if from C) MAC, Bob will simply need to ask for the key that was used to encrypt DS, Alice can see if bob’s public key can be used to decrypt the message -- this will work because if he encrypted it it will D) unlock. Alice cannot claim otherwise because no personal information of hers is bing used to generate the MAC address Password-based authentication: the system compares the password to a previously stored password for that user ID, maintained in a system password file. Token-based authentication: objects that a user possesses 3.1 In general terms, what are for the purpose of user four means of authenticating a authentication. user’s identity? Biometric authentication: attempts to authenticate an individual based on their physical characteristics. Remote user authentication: takes place over the Internet, a network or a communication link. Offline dictionary attack: the attacker obtains the system password file and compares the password hashes against hashess of commonly used passwords. Specific account account: attacker targets a specific account and submits password guesses until the correct password is discovered. Popular password attack: a variation of the preceding attack is to use a popular password and try it against a wide range of user IDs. Password guessing against a 3.2 List and briefly describe the single user: attacker attempts principal threats to the secrecy to gain knowledge about the of passwords account holder and system password policies and uses that knowledge to guess the password. Workstation hijacking: the attacker waits until a logged-in workstation is unattended. Exploiting user mistakes: reading a written down password, users sharing their password etc. Exploiting multiple password use: different network devices use the same or similar passwords for a given user. Electronic monitoring: intercepting a password communicated over a network. Often, the hashed passwords are kept in a separate file from the user IDs, referred to as a 3.3 What is the significance of a shadow password file. Special shadow password file? attention is paid to making the shadow password file protected from unauthorized access.