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Authenticating People

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Authenticating People © Jones & Bartlett Learning,© Jones LLC & Bartlett Learning LLC, an Ascend Learning© Jones Company. & NOT Bartlett FOR SALE Learning, OR DISTRIBUTION. LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC © Digital_Art/ShutterstockNOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION CHAPTER 6 © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FORAuthenticating SALE OR DISTRIBUTION PeopleNOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION ▸ About This Chapter In this chapter, we look at techniques to accurately associate individuals with user identities inside a computer. The discussion will focus on passwords with an intro- duction to© other Jones methods. & Bartlett The chapter Learning, examines the LLC following topics: © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION ■ The three authentication factors: what you know, you have, and you are ■ Passwords, password bias, and search space calculations ■ Cryptographic building blocks: random choice, one-way hash ■ Authentication devices: personal tokens and biometrics ■ © Jones &Basic Bartlett issues in Learning, authentication LLC policy © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION ▸ 6.1 Unlocking a Door We use padlocks, deadbolts, and safes to protect unattended things. We arrange it so that only authorized users may open these locks. We either restrict copies of © Jones & Bartlett keysLearning, to the trusted LLC people, or we share lock combinations© Jones with& Bartlett only those Learning, trusted LLC NOT FOR SALE ORfew. DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Bob shares his computer with his employees and with those of Alice’s Arts. Sharing causes no problems as long as neither Alice nor her employees meddle with Bob’s bookkeeping files. In FIGURE 6.1, we break the problem down into its components. On the left we have Bob, the person who wants to use the computer. He types in© a Jonesuser identity & Bartletthe wishes to Learning, use, and provides LLC a credential to prove the © Jones & Bartlett Learning, LLC identity belongsNOT toFOR him. SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION On the right of the figure, we break the computer’s problem into two separate mechanisms: authentication and access control. 1. Authentication—associates an individual with an identity inside the © Jones &computer Bartlett (this Learning, chapter). LLC © Jones & Bartlett Learning, LLC NOT FOR2. Access SALE control—checks OR DISTRIBUTION access rights and grants access to resourcesNOT FOR SALE OR DISTRIBUTION (Chapters 2–4); the list of rights depends on the authenticated user identity. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning,© Jones LLC & Bartlett Learning LLC, an Ascend Learning© Jones Company. & NOT Bartlett FOR SALE Learning, OR DISTRIBUTION. LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 224 Chapter 6 Authenticating People © Jones & Bartlett Learning, LLC Login:© Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONUser identity: AuthenticationNOT FOR SALE OR DISTRIBUTION login: bob Bob’s name inside Mechanism password: alice the computer Access Control © Jones & Bartlett Learning, LLC Credential: © JonesMechanism & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION Bob knows NOT FOR SALE OR DISTRIBUTION his password. © Jones & Bartlett Learning, TheLLC Person: © Jones & Bartlett Learning,Resources LLC NOT FOR SALE OR DISTRIBUTIONBob NOT FOR SALE OR DISTRIBUTION FIGURE 6.1 Authentication to protect computer resources. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR1. Enter SALE the OR2. TrDISTRIBUTIONansmit NOT FOR SALE OR DISTRIBUTION credential. the credential. Hard Drive © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Authentication Login: Database 3. Compare credentials. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALEFIGURE OR 6.2DISTRIBUTION Performing the authentication. NOT FOR SALE OR DISTRIBUTION When we look at physical locks, the bolt action provides the access control. When the bolt is locked, the door won’t open and the locking mechanism keeps the bolt in place. When we supply the key or combination, we release the locking © Jonesmechanism & Bartlett (“authentication”). Learning, When LLC we turn the lock, we move the© Jonesbolt to unlock & Bartlett Learning, LLC NOT FORthe door SALE (“access OR control”). DISTRIBUTION NOT FOR SALE OR DISTRIBUTION FIGURE 6.2 illustrates the steps in performing an authentication. We start with Bob, the person who possesses the credential. He enters the credential into a device that converts it to computer-readable form. For passwords and personal identification numbers (PINs), the device is a keyboard. The device transmits the © Jones & Bartlett computer-readableLearning, LLC credential into the computer’s© Jones RAM. &Inside Bartlett RAM, theLearning, login LLC NOT FOR SALE ORprocess DISTRIBUTION compares the credentials against Bob’sNOT personal FOR data SALE stored ORin the DISTRIBUTION com- puter’s authentication database. This database contains a list of every user ID the system recognizes and the data required to authenticate each user. If they don’t match, the authentication fails. If they match, login proceeds. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning,© Jones LLC & Bartlett Learning LLC, an Ascend Learning© Jones Company. & NOT Bartlett FOR SALE Learning, OR DISTRIBUTION. LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 6.1 Unlocking a Door 225 Once the login process has authenticated the user, it starts other processes on behalf of the© Jonesuser. Although & Bartlett the login Learning, process is itself LLC a system process, the new © Jones & Bartlett Learning, LLC processes NOT(“child” FOR processes) SALE it starts OR all DISTRIBUTION belong to the newly logged-in user. These NOT FOR SALE OR DISTRIBUTION processes will manage the user’s desktop and handle other tasks on that user’s behalf. Because these processes belong to the user, their access rights are restricted to those resources the user is allowed to use. Access control, as established by the access rights, is based on the authenticated user identity. © Jones &In authentication,Bartlett Learning, our objective LLC is to accurately tie the person© toJones a particular & Bartlett Learning, LLC NOT FORuser identity SALE inside OR theDISTRIBUTION computer. Computers make all of their decisionsNOT FOR based SALEon OR DISTRIBUTION information. Thus, the computer must make its decision on information that only the authorized person can provide: the credential. It must be impractical for others to forge someone’s credential. This hard-to-forge information is often—though not always—secret infor- © Jones & Bartlett mation,Learning, so we callLLC it the base secret. The system© Jones stores a copy& Bartlett of the base Learning, secret, LLC NOT FOR SALE ORor DISTRIBUTIONa specially encoded version of the base secret,NOT in the FOR authentication SALE OR database. DISTRIBUTION If an attacker acquires a copy of a user’s base secret, the attacker can masquerade as that user. If the attacker has no way of retrieving or guessing the base secret, then a masquerade is much less likely. The challenge in authentication is to establish credentials and associate them with the right© Jones people. A& successful Bartlett authentication Learning, system LLC makes it as hard as pos- © Jones & Bartlett Learning, LLC sible for oneNOT user FORto masquerade SALE asOR another DISTRIBUTION by forging a credential. Over the years NOT FOR SALE OR DISTRIBUTION the computing community has developed a variety of techniques to do this, with varying degrees of success. 6.1.1 Authentication Factors © JonesIn computer & Bartlett systems, Learning, we recognize LLC three fundamental strategies© for Jones authenticat & Bartlett- Learning, LLC NOT FORing people. SALE These OR are DISTRIBUTION called authentication factors: NOT FOR SALE OR DISTRIBUTION 1. Something You Know—memorized information like passwords or PINs. 2. Something You Have—an object containing a hard-to-copy base secret, like the magnetic stripe on a cash card or a unique code stored in a smartphone. © Jones & Bartlett 3.Learning, Something LLC You Are—a biometric measurement© Jones like fingerprints, & Bartlett voice, Learning, or LLC eye features. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION TABLE 6.1 gives examples of commonly used authentication techniques. Each example in the table represents a single factor. Each produces a credential. Each relies on a base secret. Most systems use passwords, and thus they rely on only the first of the three factors. Originating© Jones with & aBartlett pioneering Learning, timesharing systemLLC at MIT, passwords were © Jones & Bartlett Learning, LLC the first formNOT of FORcomputer-based SALE OR authentication. DISTRIBUTION Today, passwords remain the NOT FOR SALE OR DISTRIBUTION fundamental authentication technique. Even systems that use other authentication factors will have one or more password-protected logins that
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