SCU COEN 250 - Authentication Lecture Notes

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COEN 250AuthenticationHuman Machine AuthenticationSlide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Authentication Security Policy Defining Protection LevelsSlide 26Slide 27Network Access ControlSlide 29Login PoliciesUser AccountsPassword PoliciesTelecommuting / Remote Access PoliciesMobile EquipmentCOEN 250AuthenticationAuthenticationBetween human and machineBetween machine and machineHuman Machine AuthenticationAuthentication protocols are based onWhat you know.E.g. password, pass-phrase, (secret key, private key).What you have.Physical key, smart card.What you are.Biometrics.Where you are.E.g. trusted machine, access to room, …AuthenticationPasswordsPredate computers.As do some attacks (stealing, guessing)Older cell phone technology transmits originating number with a password.Password good, call goes through.Eavesdropper receives phone number – password combination.Eavesdropper can now cl one the phone.AuthenticationPassword AttacksGuessingOn-lineTime consuming.Authentication attempts are usually logged.Can detect attack long before it is likely to succeed.Can disrupt the attack.Off-lineAttacker needs to steal relevant data from which password(s) can be determined.Attacker can use arbitrary amount of computing power.Capturing PasswordsEavesdroppingLogin Trojan HorseAuthenticationPasswords are storedOn each server Alice uses.Centrally: Authentication Storage Node:Each server retrieves the information when it wants to authenticate Alice.Centrally: Authentication Facilitator Node:Each server takes Alice’s data and password and goes to the AFN.AuthenticationPassword can be storedUnencryptedSimpleDangerousImplicitly as hashes of passwordsAs in UNIX, VMSEncryptedHashed and EncryptedAuthenticationExample: Network Information Service(Yellow Pages)Directory service is the authentication storage node.Stores hashed passwords of users.Typically, hashed passwords list is world readable Access by claiming to be a server.NIS authentication storage node does not authenticate itself to users.Allows impersonation of authentication service.AuthenticationPasswords for machine – machine communication can be made difficult to guess.Arbitrary lengthTruly random choice of characters.Human-machine passwordsGuessableSubject to dictionary attack.AuthenticationDictionary attackMost passwords are natural language words.Or derived from natural language words.Guess the language.Use a dictionary to try out all words in the language.Start with common passwords first.Replace a single character in a word, attach a random character, etc.AuthenticationBrute-Force AttackGenerate all possible password.Sometimes make assumptions on the alphabet only printable charactercharacters on a key-boardAuthenticationSalting Protects hashed passwords against an offline attack.Brute Force attack attacks all passwords in password file simultaneously.AuthenticationSaltingStore a salt with each passwordHash depends on salt and password.Use different salts for different passwords.Store salt with password.AuthenticationSaltingBrute force attack, dictionary attack can only attack a single password.AuthenticationPasswords are compromised:By obtaining password file.Safeguard byHashing and SaltingEncryptionBy eavesdropping on an exchangeUse one-way passwords:Lamport HashAuthenticationAddress BasedCommon in early UNIXRtools:.rhosts In user home directory(Computer, Account) pairsThese pairs are allowed access to the user’s account/etc/hosts.equivList of network addresses of “equivalent” machinesAccount name on A is equivalent to account name on B.Users have to have identical account names.AuthenticationAddressed based authentication threatened byAccess escalationAttacker gains access to one hosts.Access cascades to equivalent hosts / rhosts.Spoofing addressesVery easy to spoof source address.Harder to intercept traffic back.AuthenticationEthernet network address impersonationEasy on the same link.Hubs do not protect.Switches can be spoofed through the ARP protocol.Routers are harder to fool, but can be attacked and provided with misleading routing data.AuthenticationCryptographic authenticationAlice proves her identity to Bob by proving to Bob that she knows a secret.HashesSecret key cryptographyPublic key cryptography.Human Machine AuthenticationInitial password distribution to humansPre-expired, strong passwordsThrough mailDerivable from common knowledgeStudent IDHuman Machine AuthenticationAuthentication TokenPossession of the token proves right to access.Magnetic stripe as on credit cards.Harder to reproduce“Impossible” to guessDemand special hardwareCan be lost or stolenAdd pin or password protectionAre not safe against communication eavesdropping and forgingHuman Machine AuthenticationAuthentication TokenSmart Card.Needs to be inserted in a smart card reader.Card authenticates to the smart card reader.PIN protected smart cards.Stops working after a number of false PINs.Cryptographic challenge / response cardsCard contains a cryptographic key.Authenticating computer issues a challenge.Card solves the challenge after PIN is entered.Harder to crack than PIN protected smart cards because key is never revealed.Human Machine AuthenticationAuthentication TokenSmart Card.Readerless smart card (Cryptographic calculator)Communicates with owner through mini-keyboard and display.Authenticating computer issues a challenge to Alice.Alice types in challenge into readerless smart card.Readerless smart card solves the challenge.After Alice puts in her password.Alice transfers the answer to the computer.Human Machine AuthenticationBiometricsRetinal scannerFingerprint readerFace recognitionIris scannerHandprint readersVoiceprintsKeystroke timingSignaturesAuthentication Security PolicyDefining Protection LevelsPartitioning Computing ResourcesUsually necessary (law) to have special security for sensitive areas:Human


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SCU COEN 250 - Authentication Lecture Notes

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