1 / 31

CSC 382/582: Computer Security

Learn about computer security authentication, network identities, biometrics, and more in this comprehensive guide. Understand the purpose of identity access control and different types of authentication methods.

tpolk
Download Presentation

CSC 382/582: Computer Security

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CSC 382/582: Computer Security Authentication CSC 382/582: Computer Security

  2. Authentication • Identity • Groups and Roles • Network Identities • Authentication • Biometrics • UNIX Authentication CSC 382/582: Computer Security

  3. What is Identity? Computer’s representation of an entity • Entities can be subjects or objects. Authentication binds a principal to an identity. Example: • username expresses your identity. • password binds the person typing to that particular identity (username). CSC 382/582: Computer Security

  4. Purpose of Identity Access Control • Most systems base access rights on identity of principal executing the process. Accountability • Logging and auditing functions. • Need to track identity across account/role changes (e.g., su, sudo). CSC 382/582: Computer Security

  5. Groups and Roles An “entity” may be a set of entities referred to by a single identifier. Principals often need to share access to files, and thus are taken as groups. • static: alias for a group of principles. • dynamic: principal changes from one group to another as different privileges are needed. role: a group that ties membership to function CSC 382/582: Computer Security

  6. Network Identity Ethernet (MAC) Address • 48-bit data link level identifier • example: 00:0B:DB:78:39:8A IP Address • 32-bit network level identifier • ex: 10.17.0.101 IPv6 Address • 128-bit network level identifier • ex: fe80::2a0:c9ff:fe97:153d/64 Hostname (DNS name) • string application level identifier • ex: www.nku.edu CSC 382/582: Computer Security

  7. What is Authentication? Binding of an identity to a subject Based on: • What the entity knows (e.g., passwords) • What the entity has (e.g., access card) • What the entity is (e.g., fingerprints) • Where the entity is (e.g., local terminal) Two-factor authentication CSC 382/582: Computer Security

  8. What You Know • Passwords • Pass Phrases • PINs CSC 382/582: Computer Security

  9. What You Have • Smart Cards • USB Token • RFID RFID used for toll collection CSC 382/582: Computer Security

  10. USB Tokens and Smart Cards • Small device with storage and processor. • USB tokens tend to focus on storage. • Smart cards on processor + small storage. • Differences are growing smaller. • Methods of use • By Hand (read card and type one-time password) • USB • Wireless CSC 382/582: Computer Security

  11. RFID • Radio Frequency Identification • Types of Tags • Passive: use power from reader signal • Active: internal power source • Applications • Product tracking (EPC barcode replacement) • Transportation payment • Automotive (embedded in car keys) • Passports • Human implants EPC RFID Tag CSC 382/582: Computer Security

  12. What You Are: Biometrics Identification by human characteristics: • Physiological • Behavioral A biometric characteristic should be: • universal: everyone should have it • unique: no two people should share it • permanent: it should not change with time • quantifiable: it must be practically measurable CSC 382/582: Computer Security

  13. How Biometrics Work • User submits sample. • Software turns sample into digital template. • Software compares template against stored reference template. • Authentication based on how closely templates match. CSC 382/582: Computer Security

  14. Biometric Measurement Possible Outcomes: • Correct person accepted • Imposter rejected • Correct person rejected (False Rejection) • Imposter accepted (False Acceptance) CSC 382/582: Computer Security

  15. False Positives and Negatives Tradeoff between • False Accept Rate • False Reject Rate CSC 382/582: Computer Security

  16. Fingerprints Capacitive measurement, using differences in electrical charges of whorls on finger to detect those parts touching chip and those raised. CSC 382/582: Computer Security

  17. Brandon Mayfield • Fingerprints found in 2004 Madrid bombing. • Brandon arrested May 6, 2004. • FBI claimed “100 percent positive” match. • Held under a false name. • Then transferred to unidentified location. • Spanish police identify fingerprint as belonging to an Algerian man May 21, 2004. • Brandon released May 25, 2004. CSC 382/582: Computer Security

  18. Eye Biometrics • Iris Scan • Lowest false accept/reject rates of any biometric. • Person must hold head still and look into camera. • Retinal Scan • Cataracts and pregnancy change retina pattern. • Lower false accept/reject rates than fingerprints. • Intrusive and slow. CSC 382/582: Computer Security

  19. Physiological DNA Face recognition Hand geometric Scent detection Voice recognition Behavioral Gait recognition Keyboard dynamics Mouse dynamics Signatures Other Types of Biometrics CSC 382/582: Computer Security

  20. Biometrics are not infallible What are False Accept and Reject Rates? Do the characteristics change over time? • Retina changes during pregnancy. • Fingerprint damage due to work/pipe smoking. • Young and old people have fainter fingerprints. Is it accurate in the installed environment? • Is someone observing fingerprint or voiceprint checks? • i.e., did you collect biometric from the person? CSC 382/582: Computer Security

  21. Biometrics can be compromised. Unique identifiers, not secrets. • You can change a password. • You can’t change your iris scan. Examples: • You leave your fingerprints every place. • It’s easy to take a picture of your face. Other compromises. • Use faux ATM-style devices to collect biometrics. • Obtain all biometric templates from server. CSC 382/582: Computer Security

  22. Use and Misuse of Biometrics Employee identification. • Employee enters login name. • System uses fingerprint to verify employee is who he claims to be. • Problem: Does biometric match the employee? Criminal search (Superbowl 2001) • System uses face recognition to search for criminals in public places. • Problem: Does any biometric in database match anyone in a crowd of people? • Assume system is 99.99% accurate and 1 in 10million people is a terrorist. Result: 1000 false positives for each terrorist. CSC 382/582: Computer Security

  23. Location Classic: only allow access from a particular terminal or a particular set of remote hosts. Modern: GPS-based • Location Signature Sensor (LSS) for host and user. • Access rules permit user only to access host with specific LSS values. • Cell-phones track location, and some states use them to track drivers’ speed and locations. CSC 382/582: Computer Security

  24. UNIX Authentication • UNIX identifies user with a UID • Username is for humans, UID for computers. • 15-bit to 32-bit unsigned integer. • UID=0 is the superuser, root. • Identity and authentication data stored in • /etc/passwd • /etc/shadow • /etc/group CSC 382/582: Computer Security

  25. /etc/passwd Username UID Default GID GCOS Home directory Login shell /etc/shadow Username Encrypted password Date of last pw change. Days ‘til change allowed. Days `til change required. Expiration warning time. Expiration date. /etc/{passwd,shadow} Central file(s) describing UNIX user accounts. student:x:1000:1000:Example User,,555-1212,:/home/student:/bin/bash student:$1$w/UuKtLF$otSSvXtSN/xJzUOGFElNz0:13226:0:99999:7::: CSC 382/582: Computer Security

  26. Groups and GIDs • GIDs are 32-bit non-negative integers. • Each user has a default GID. • File group ownership set to default GID. • Temporarily change default GID: newgrp. • Groups are described in /etc/group • Users may belong to multiple groups. • Format: group name, pw, GID, user list. • wheel:x:10:root,waldenj,bergs CSC 382/582: Computer Security

  27. Superuser can Read any file. Modify any file. Add / remove users. Become any user. Kill any process. Reprioritize processes. Configure network. Set date/time. Shutdown / reboot. Superuser can’t Change read-only filesystem. Decrypt hashed passwords. Modify NFS-mounted filesystems. Read or modify SELinux protected files. Superuser Powers CSC 382/582: Computer Security

  28. Switching Users The su command allows you to switch users. > id uid=102(wj) gid=102(wj) groups=102(wj) > su Password: # id uid=0(root) gid=0(root) groups=0(root),1(bin),2(daemon),3(sys),4(adm), 6(disk),10(wheel) # su john john$ id uid=1995(john) gid=1995(john) groups=1995(john) john$ exit # exit > id uid=102(wj) gid=102(wj) groups=102(wj) CSC 382/582: Computer Security

  29. Real and Effective UIDs • Real UID • The UID matching the username you logged in as. • Effective UID • The UID that is checked for access control. • The su command changes your EUID. • SUID programs • A SUID program executes with an EUID of the owner of the program instead of yours. • /usr/bin/passwd is SUID root. Why? CSC 382/582: Computer Security

  30. Key Points • Access control is based on identity. • Authentication consists of an entity, the user, attempting to convince another entity, the verifier, of the user’s identity • something you know • something you have • something you are • Authentication Types • Passwords • Security Tokens • Biometrics CSC 382/582: Computer Security

  31. References • Phil Agre. “Your Face is not a Bar Code,” http://polaris.gseis.ucla.edu/pagre/bar-code.html, 2003. • Ross Anderson, Security Engineering, Wiley, 2001. • Matt Bishop, Introduction to Computer Security, Addison-Wesley, 2005. • DigitalPersona, http://www.digitalpersona.com/company/news/pressKit.php, 2006. • Simson Garfinkel, Gene Spafford, and Alan Schwartz, Practical UNIX and Internet Security, 3/e O’Reilly, 2003. • Ben Mook, “Md. pilot program tracks drivers’ speed, location via cell phones,” The Daily Record, October 21, 2005, http://www.mddailyrecord.com/pub/5_398_friday/businessnews/172883-1.html • Bruce Schneier, “Biometrics: Truths and Fictions,” Cryptogram, http://www.schneier.com/crypto-gram-9808.html#biometrics, 1998. • Bruce Schneier, “The Curse of the Secret Question,” http://www.schneier.com/essay-081.html, 2005. • Ed Skoudis, Counter Hack Reloaded, Prentice Hall, 2006. • Wikipedia, http://en.wikipedia.org/wiki/Biometrics, 2006. • Wikipedia, http://en.wikipedia.org/wiki/Fingerprint, 2006. • Wikipedia, http://en.wikipedia.org/wiki/Iris_%28anatomy%29, 2006. • Wikipedia, http://en.wikipedia.org/wiki/RFID, 2006. • Wikipedia, http://en.wikipedia.org/wiki/Security_token, 2006. • Orville Wilson, “Privacy & Identity - Security and Usability: The viability of Passwords & Biometrics,” http://facweb.cs.depaul.edu/research/vc/CIPLIT2004/ppt/Orville_Wilson.ppt, 2004. • “Simple Anatomy of the Retina,” http://webvision.med.utah.edu/sretina.html, 2006. CSC 382/582: Computer Security

More Related