Chapter 3_v2 _bf8fe41fd618d55d749625c8e9c1c10a.pdf

Cybersecurity Fundamentals (CY 101) Chapter 3: User Authentication  Outline Ø Digital User Authentication Principles ØPassword-Based Authentication ØToken-Based Authentication ØBiometric Authentication ØSecurity Issues for User Authentication ...

Cybersecurity Fundamentals (CY 101) Chapter 3: User Authentication  Outline Ø Digital User Authentication Principles ØPassword-Based Authentication ØToken-Based Authentication ØBiometric Authentication ØSecurity Issues for User Authentication  Digital User Authentication Digital Identity is “A unique representation of a subject engaged in an online transaction.” NIST SP 800-63-3 (Digital Authentication Guideline, June 2017) Digital user authentication is the process of determining the validity of one or more authenticators used to claim a digital identity.  Security Requirements For Identification And Authentication Table 3.1, from NIST SP 800-171 (Protecting Controlled Unclassified Information in Nonfederal Information Systems and Organizations, February 2020), provides a useful list of security requirements for identification and authentication services. ØBasic Security Requirements: 1. Identify information system users, processes acting on behalf of users, or devices. 2. Authenticate (or verify) the identities of those users, processes, or devices, as a prerequisite to allowing access to organizational information systems. ØDerived Security Requirements: 3. Use multifactor authentication for local and network access to privileged accounts and for network access to non-privileged accounts. Security Requirements For Identification And Authentication (cont’d.) 4. Employ replay-resistant authentication mechanisms for network access to privileged and non-privileged accounts. 5. Prevent reuse of identifiers for a defined period. 6. Disable identifiers after a defined period of inactivity. 7. Enforce a minimum password complexity and change of characters when new passwords are created. 8. Prohibit password reuse for a specified number of generations. 9. Allow temporary password use for system logons with an immediate change to a permanent password. 10. Store and transmit only cryptographically-protected passwords. 11. Obscure feedback of authentication information. A Model for Digital User Authentication Figure 3.1 The NIST SP 800-63-3 E-Authentication Architectural Model  Means of Authentication There are four general means of authenticating a user’s identity, which can be used alone or in combination: Something the individual Something the individual Something the individual is Something the individual knows possesses (token) (static biometrics) does (dynamic biometrics) Password, PIN, answers to Smartcard, electronic keycard, Fingerprint, retina, face Voice pattern, handwriting, prearranged questions physical key typing rhythm  Multifactor Authentication ØMultifactor authentication (MFA) refers to an authentication process where the user presents two or more pieces of evidence (or factors) to verify their identity.  Assurance Levels for User Authentication ØAn organization can choose from a range of authentication technologies, based on the degree of confidence in identity proofing and authentication processes ØNIST SP 800-63-3 defines three separate levels for each of Identity Assurance Level (IAL) and Authenticator Assurance Level (AAL). ØThree levels of IALs IAL1: No need to link the applicant to a specific real-life identity IAL2: Provides evidence for the claimed identity using either remote or physically-present identity proofing IAL3: Requires physical presence for identity proofing. Assurance Levels for User Authentication (cont’d.) ØThree levels of AALs AAL1: Provides some assurance of authentication via user-supplied ID and password. AAL2: Provides high confidence of authentication via proof of possession and control of two authentication factors AAL3: Provides very high confidence of authentication via proof of possession and control of two authentication factors  Password-Based Authentication ØA widely used line of defense against intruders is the password system. ØPassword-Based Authentication contains a username/login (ID) and password. ØThe password serves to authenticate the ID of the individual logging on to the system. ØThe system compares the password to a previously stored password for that user ID, maintained in a system password file. ØIn turn, the ID provides security in the following ways: The ID determines whether the user is authorized to gain access to a system. The ID determines the privileges accorded to the user. The ID is used in what is referred to as discretionary access control.  Password Vulnerabilities ØThe main forms of attack against password-based authentication Password Offline Specific account Popular guessing against dictionary attack attack password attack single user Exploiting Workstation Exploiting user Electronic multiple hijacking mistakes monitoring password use  The Use of Hashed Passwords ØA widely used password security technique is the use of hashed passwords and a salt value. ØPassword hashing: § turns the password into a fixed-length (string of letters and/or numbers) using a hashing algorithm. § The password hashing helps prevent cybercriminals from getting access to the passwords file. ØSalt value: § is a secret pseudorandom or random string that is combined with a password § the salt serves three purposes: It prevents duplicate passwords from being visible in the password file. It greatly increases the difficulty of offline dictionary attacks. It becomes nearly impossible to find out whether a person with passwords on two or more systems has used the same password on all of them.  The Use of Hashed Passwords ØThe hashed password scheme is found on virtually all UNIX variants as well as on a number of other operating systems. ØThe hash algorithm is designed to be slow to execute in order to thwart attacks. ØThis method has been shown to be secure against a variety of cryptanalytic attacks Figure 3.3: UNIX Password Scheme  UNIX Implementation ØOriginal scheme Up to 8 printable characters in length 12-bit salt used to modify DES encryption into a one-way hash function Zero value repeatedly encrypted 25 times Output translated to 11 character sequence ØNow regarded as inadequate Still often required for compatibility with existing account management software or multivendor environments  Improved Implementations ØMuch stronger hash/salt schemes available for Unix ØRecommended hash function is based on MD5 Salt of up to 48-bits Password length is unlimited Produces 128-bit hash Uses an inner loop with 1000 iterations to achieve slowdown ØOpen BSD uses Blowfish block cipher based hash algorithm called Bcrypt Most secure version of Unix hash/salt scheme Uses 128-bit salt to create 192-bit hash value  Password Cracking ØDictionary attacks Develop a large dictionary of possible passwords and try each against the password file Each password must be hashed using each available salt value and then compared with stored hash values ØRainbow table attacks Pre-compute tables of hash values for all salts A mammoth table of hash values Can be countered by using a sufficiently large salt value and a sufficiently large hash length ØPassword crackers exploit the fact that people choose easily guessable passwords Shorter password lengths are also easier to crack ØJohn the Ripper Open-source password cracker first developed in 1996 Uses a combination of brute-force and dictionary techniques  Exercises 1) An attacker plans to gain unauthorized access to a system by systematically trying all possible words or combinations from a pre- existing list. What is the term for this type of attack? Dictionary attacks 2) An attacker plans to use a rainbow table to crack passwords. Suggest how an organization can defend against such attacks. Use sufficiently large and unique salt values for each user's password, making pre- computation impractical due to the vast number of possible hash values. 3) Why are shorter password lengths easier to crack? Shorter password lengths are easier to crack because they have fewer possible combinations, making them more susceptible to brute-force and dictionary attacks. Modern Approaches However password- Complex password cracking techniques policy have also improved The processing capacity The use of sophisticated Studying examples and Forcing users to pick available for password algorithms to generate structures of actual stronger passwords cracking has increased potential passwords passwords in use dramatically  The Percentage of Passwords Guessed after a Given Number of Guesses Figure 3.4  Password File Access Control Can block offline guessing attacks by denying access to encrypted passwords Make available only to privileged users Shadow password file Vulnerabilities Weakness in the OS that allows access to the file Accident with permissions making it readable Users with same password on other systems Access from backup media Sniff passwords in network traffic  Password Selection Strategies Computer generated Reactive password Complex password User education passwords checking policy Users can be told Users have trouble System periodically User is allowed to the importance of remembering them runs its own select their own using hard to guess password cracker to password, however passwords and can find guessable the system checks be provided with passwords to see if the guidelines for password is selecting strong allowable, and if passwords not, rejects it Goal is to eliminate guessable passwords while allowing the user to select a password that is memorable  Proactive Password Checking Rule Password Bloom filter enforcement checker Specific rules Compile a Used to build a that passwords large table based on must adhere to dictionary of hash values passwords not Check desired to use password against this table  Token-Based Authentication ØObjects that a user possesses for the purpose of user authentication are called tokens ØTwo types of tokens that are widely used; these are Card-Based Tokens Hardware Tokens ØAdditionally, there's a growing trend in using mobile phones for authentication purposes. Users can authenticate themselves using their mobile phones in two primary ways: SMS Messages Software Apps  Memory Cards ØMemory Card Can store but do not process data The most common card is a bank card with a magnetic stripe on the back. Can include an internal electronic memory ØCan be used alone for physical access Hotel room Gift card ØProvides significantly greater security when combined with a password or PIN ØDrawbacks of memory cards include: Requires a special reader Loss of token User dissatisfaction  Smart Tokens A wide variety of devices qualify as smart tokens. These can be categorized along four dimensions that are not mutually exclusive: Physical Electronic Authentication User interface: characteristics: interface protocol: Include an embedded Manual interfaces A smart card or other Classified into three microprocessor include a keypad and token requires an categories: A smart token that display for electronic interface Static looks like a bank card human/token to communicate with Dynamic password generator Challenge-response interaction a compatible Can look like reader/writer calculators, keys, small portable Contact and objects contactless interfaces  Smart Cards ØFor user authentication, the most important category of smart token is the smart card Has the appearance of a credit card Has an electronic interface May use any of the smart token protocols ØA smart card contains within it an entire microprocessor, including Processor memory I/O ports  Smart Cards (cont’d.) ØTypically include three types of memory: Read-only memory (ROM) Stores data that does not change during the card’s life Electrically erasable programmable ROM (EEPROM) Holds application data and programs Random access memory (RAM) Holds temporary data generated when applications are executed  Electronic Identity Cards (eID) ØUse of a smart card as a national identity card for citizens Can serve the same purposes as other national ID cards, and similar cards such as a driver’s license, for access to government and commercial services Can provide stronger proof of identity and can be used in a wider variety of applications In effect, is a smart card that has been verified by the national government as valid and authentic ØMost advanced deployment is the German card neuer Personalausweis Has human-readable data printed on its surface § Personal data § Document number § Card access number (CAN) § Machine readable zone (MRZ)  Eid Functions The card has the following three separate electronic functions, each with its own protected dataset PAC E Function Purpose Data Uses Password e Pass Authorized offline CAN or MRZ Face image; two fingerprint images Offline biometric identity (mandatory) inspection systems read (optional); MRZ data verification reserved for the data. government access eID (activation Online applications read eID PIN Family and given names; artistic name Identification; age verification; optional) the data or access and doctoral degree; date and place of community ID verification; functions as authorized. birth; address and community ID; restricted identification expiration date (pseudonym); revocation query Offline inspection CAN or MRZ Family and given names; artistic name Identification; age verification; e I D (activation optional systems read the data and doctoral degree; date and place of community ID verification; and update the address birth; address and community ID; restricted identification and community I D. expiration date (pseudonym); revocation query  Eid Functions (cont’d.) Function Purpose PAC E Password Data Uses eSign (certificate A certification authority eID PIN Signature key; X.509 Electronic signature optional) installs the signature certificate creation certificate online. Citizens make electronic CAN Signature key; X.509 Electronic signature eSign (certificate optional) signature with eSign PI certificate creation N. CAN = card access number M RZ = machine-readable zone PACE = password authenticated connection establishment PI N = personal identification number  User Authentication with eID User authentication is a good example of online use of the eID function. Figure 3.6 illustrates a Web-based scenario  Password Authenticated Connection ØPassword Authenticated Connection Establishment (PACE) ensures that the contactless RF chip in the eID card cannot be read without explicit access control. For online applications, For offline applications, Ensures that the access is established by either the MRZ printed on contactless RF chip in the the user entering the six- the back of the card or the eID card cannot be read digit PIN (which should be six-digit card access without explicit access known only to the holder number (CAN) printed on control of the card) the front is used  Hardware Authentication Tokens ØOne-time password (O T P) device: Has a secret key to generate an OTP User enters the OTP and the system validates the value entered Uses a block cipher/hash function to combine secret key and time or nonce value to create OTP Has a tamper-resistant module for secure storage of the secret key  Hardware Authentication Tokens (cont’d.) ØTime-based one-time password (TOTP): Uses HMAC with a hash function Used in many hardware tokens and by many mobile authenticator apps Password is computed from the current Unix format time value ØSystems using time based OTP need to allow for clock drift between token and verifying system ØSystems using nonce need to allow for failed authentication attempts  Hardware Authentication Tokens (cont’d.) ØDisadvantage: any other person can see the code ØAlternative: use of a communications link ØSingle-factor vs. multifactor: Single-factor: provides authentication service with just one factor Multifactor: provides authentication service after a local authentication step ØFIDO2 Includes “WebAuthn” standard and “Client to Authenticator Protocol 2 (CTAP2)” Uses a user agent as an intermediary between authenticator and authenticating service Prominent members: Google and Microsoft  Exercises ØTo bolster security measures, a bank is considering implementing token- based authentication within its mobile banking application. Taking into account the diverse range of token options available, what specific types of tokens should the bank choose to ensure optimal security and user experience? Time-Based One-Time Password (TOTP) Tokens TOTP tokens generate unique passwords that expire after a short period, typically 30 seconds. These tokens are highly secure and convenient for users  Authentication Using a Mobile Phone ØAuthentication code via message: One of the simplest authentication approaches Used for banking, government service access, etc. No need to have any additional app on the phone Disadvantage: § Requires mobile coverage to receive SMS § When mobile phone is lost or stolen, user will lose access or an attacker might gain access § Attackers might use a SIM swap attack § Attacker might also intercept messages using either a fake mobile tower, or by attacking SS7 signaling protocol  Authentication Using a Mobile Phone (cont’d.) ØMobile authentication apps: Implements a one-time password generator Implements the “Time-based one-time password (TOTP)” algorithm Does not require a network connection Can be used with multiple accounts More secure than authentication code Disadvantages: § Phone might be lost or stolen § Attacker might compromise by installing malware § Attacker might convince the user to reveal secret code  Biometric Authentication ØAttempts to authenticate an individual based on unique physical characteristics ØBased on pattern recognition ØIs technically complex and expensive when compared to passwords and tokens ØPhysical characteristics used include: ØFacial characteristics ØFingerprints Hand geometry Retinal pattern Iris Signature Voice  Cost versus Accuracy of Various Biometric Characteristics in User Authentication Schemes Figure 3.7  Remote User Authentication ØAuthentication over a network, the Internet, or a communications link is more complex ØAdditional security threats such as: Eavesdropping, capturing a password, replaying an authentication sequence that has been observed ØGenerally rely on some form of a challenge-response protocol to counter threats Basic Challenge- Response Protocols for Remote User Authentication Figure 3.12  Security Issues for User Authentication As with any security service, user authentication, particularly remote user authentication, is subject to a variety of attacks Attacks Authenticators Examples Typical Defenses Password Guessing, exhaustive search Large entropy; limited attempts Token Exhaustive search Large entropy; limited attempts; theft of object Client attack requires presence Biometric False match Large entropy; limited attempts Password Plaintext theft, Hashing; large entropy; protection of password dictionary/exhaustive search database Token Passcode theft Same as password; 1-time passcode Host attack Biometric Template theft Capture device authentication; challenge response Eavesdropping, Password “Shoulder surfing” User diligence to keep secret; administrator theft, and copying diligence to quickly revoke compromised passwords; multifactor authentication  Security Issues for User Authentication (cont’d.) Attacks Authenticators Examples Typical Defenses Eavesdropping, Token Theft, counterfeiting Multifactor authentication; tamper theft, and copying hardware resistant/evident token Biometric Copying (spoofing) biometric Copy detection at capture device and capture device authentication Password Replay stolen password Challenge-response protocol response Token Replay stolen passcode Challenge-response protocol; 1-time passcode Replay response Biometric Replay stolen biometric Copy detection at capture device and capture template response device authentication via challenge-response protocol Trojan horse Password, token, Installation of rogue client or Authentication of client or capture device within biometric capture device trusted security perimeter Denial of service Password, token, Lockout by multiple failed Multifactor with token biometric authentications  Client Attacks: Adversary attempts to achieve user authentication without access to the remote host or the intervening communications path Host Attacks: Directed at the user file at the host where passwords, token passcodes, or biometric templates are stored Authentication Eavesdropping: Adversary attempts to learn the password by some sort of attack that involves the physical proximity of user Authentication Security Issues and adversary Security Issues Replay: Adversary repeats a previously captured user response Trojan Horse: An application or physical device masquerades as an authentic application or device for the purpose of capturing a user password, passcode, or biometric Denial-of-Service: Attempts to disable a user authentication service by flooding the service with numerous authentication attempts General Iris Scan Site Architecture for UAE System Authentication Security Issues Figure 3.13  Case Study: ATM Security Problems ØMost small to mid-sized issuers of debit cards contract processors to provide core data processing and electronic funds transfer (EFT) services. The bank’s ATM machine may link directly to the processor or to the bank. Figure 3.14: ATM Architectures Questions/Comments?