Computer Security and Privacy Autumn 2018 Tadayoshi (Yoshi) Kohno - - PowerPoint PPT Presentation

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Computer Security and Privacy Autumn 2018 Tadayoshi (Yoshi) Kohno - - PowerPoint PPT Presentation

Aug 29, 2022 107 likes •502 views

CSE 484 / CSE M 584: Computer Security and Privacy Autumn 2018 Tadayoshi (Yoshi) Kohno yoshi@cs.washington.edu Thanks to Dan Boneh, Dieter Gollmann, Dan Halperin, Ada Lerner, John Manferdelli, John Mitchell, Franziska Roesner, Vitaly

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SLIDE 1

CSE 484 / CSE M 584: Computer Security and Privacy

Autumn 2018 Tadayoshi (Yoshi) Kohno yoshi@cs.washington.edu

Thanks to Dan Boneh, Dieter Gollmann, Dan Halperin, Ada Lerner, John Manferdelli, John Mitchell, Franziska Roesner, Vitaly Shmatikov, Bennet Yee, and many others for sample slides and materials ...

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SLIDE 2

Announcements / Answers

  • If you’re on the class mailing list, you should

have received an email (about office hours this week).

  • Ethics form: Due next Wednesday (10/3).
  • Homework #1: Due next Friday (10/5) – start

forming groups, feel free to use forum.

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SLIDE 3

Announcements / Answers

  • No quiz section on Thanksgiving Day
  • No lecture on the Wednesday before

Thanksgiving day: Video assignment instead

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SLIDE 4

Last Time + Quiz Section

  • Importance of the security mindset

– Challenging design assumptions – Thinking like an attacker

  • There’s no such thing as perfect security

– But, attackers have limited resources – Make them pay unacceptable costs to succeed!

  • Defining security per context: identify assets,

adversaries, motivations, threats, vulnerabilities, risk, possible defenses

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SLIDE 5

Example: Modern Automobiles

Modern automobiles contain dozens of computers. Those computers control nearly everything in the car, including locks, lights, brakes, the engine, the airbags, etc.

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Who might want to attack? Why, and how?

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SLIDE 6

Practicing Security Mindset

  • See worksheet, Q3

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SLIDE 7

SECURITY GOALS (“CIA”) (QUIZ SECTION AND TODAY)

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SLIDE 8

Confidentiality (Privacy)

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network

  • Confidentiality is concealment of information.

Eavesdropping, packet sniffing, illegal copying

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SLIDE 9

Integrity

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network

  • Integrity is prevention of unauthorized changes.

Intercept messages, tamper, release again

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SLIDE 10

Authenticity

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network

Unauthorized assumption of another’s identity

  • Authenticity is knowing who you’re talking to.
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SLIDE 11

Availability

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network

  • Availability is ability to use information or resources.

Overwhelm or crash servers, disrupt infrastructure

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SLIDE 12

THREAT MODELING

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SLIDE 13

Threat Modeling (Security Reviews)

  • Assets: What are we trying to protect? How

valuable are those assets?

  • Adversaries: Who might try to attack, and why?
  • Vulnerabilities: How might the system be weak?
  • Threats: What actions might an adversary take to

exploit vulnerabilities?

  • Risk: How important are assets? How likely is

exploit?

  • Possible Defenses

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SLIDE 14

Example: Electronic Voting

  • Popular replacement to

traditional paper ballots

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SLIDE 15

Pre-Election

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Ballot definition file

Pre-election: Poll workers load “ballot definition files” on voting machine.

Poll worker

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SLIDE 16

Active Voting

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Voter token Voter token Interactively vote Ballot definition file

Active voting: Voters obtain single-use tokens from poll workers. Voters use tokens to activate machines and vote.

Voter Poll worker

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SLIDE 17

Active Voting

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Encrypted votes Voter token Voter token Interactively vote Ballot definition file

Active voting: Votes encrypted and stored. Voter token canceled.

Voter Poll worker

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SLIDE 18

Post-Election

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si.edu si.edu

Voter token Tabulator Voter token Interactively vote Ballot definition file

Post-election: Stored votes transported to tabulation center.

Encrypted votes Recorded votes

Voter Poll worker

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SLIDE 19

Security and E-Voting (Simplified)

  • Functionality goals:

– Easy to use, reduce mistakes/confusion

  • Security goals:

– Adversary should not be able to tamper with the election outcome

  • By changing votes (integrity)
  • By voting on behalf of someone (authenticity)
  • By denying voters the right to vote (availability)

– Adversary should not be able to figure out how voters vote (confidentiality)

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SLIDE 20

Can You Spot Any Potential Issues?

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si.edu si.edu

Voter token Tabulator Voter token Interactively vote Ballot definition file Encrypted votes Recorded votes

Voter Poll worker

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SLIDE 21

Q1 and Q2 on the Worksheet

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SLIDE 22

Potential Adversaries

  • Voters
  • Election officials
  • Employees of voting machine manufacturer

– Software/hardware engineers – Maintenance people

  • Other engineers

– Makers of hardware – Makers of underlying software or add-on components – Makers of compiler

  • ...
  • Or any combination of the above

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What Software is Running?

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Problem: An adversary (e.g., a poll worker, software developer, or company representative) able to control the software or the underlying hardware could do whatever he or she wanted.

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SLIDE 24

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SLIDE 25

Bad file Tabulator Voter token Interactively vote Ballot definition file Encrypted votes

Problem: Ballot definition files are not authenticated. Example attack: A malicious poll worker could modify ballot definition files so that votes cast for “Mickey Mouse” are recorded for “Donald Duck.”

Recorded votes

Voter Poll worker

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SLIDE 26

Voter token Interactively vote Ballot definition file

Problem: Smartcards can perform cryptographic operations. But there is no authentication from voter token to terminal. Example attack: A regular voter could make his or her own voter token and vote multiple times.

Tabulator Encrypted votes Recorded votes

Voter Poll worker

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SLIDE 27

Ballot definition file Tabulator Encrypted votes

Problem: Encryption key (“F2654hD4”) hard-coded into the software since (at least) 1998. Votes stored in the order cast. Example attack: A poll worker could determine how voters vote.

Recorded votes Voter Voter token Interactively vote

Voter Poll worker

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Ballot definition file Tabulator Encrypted votes

Problem: When votes transmitted to tabulator over the Internet

  • r a dialup connection, they are decrypted first; the cleartext

results are sent the the tabulator. Example attack: A sophisticated outsider could determine how voters vote.

Voter token Interactively vote Recorded votes

Voter Poll worker

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SLIDE 29

Tables Often Help!

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Example Table 1

Attacker “Positions” Machine Manufacturer Poll Worker Voter Power Company Employee Voter Privacy Vote Integrity Voting Machine Availability …

  • What can different parties do? Each cell would have an

action or actions that these parties might try do

  • Note that some parties could collaborate
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SLIDE 31

Example Table 2

Attack Methods Modify Software Produce Fake Voter Tokens Steal Flash Drive Intercept Network Connections Voter Privacy Vote Integrity Voting Machine Availability …

  • What different attack methods are there? (Columns)
  • Who could mount these different attacks? What are the

attack details (the cells)

  • How easy is it to implement each of these attack

methods?

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SLIDE 32

Table from Paper

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https://homes.cs.washington.edu/~yoshi/papers/eVoting/vote.pdf

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SLIDE 33

TOWARDS DEFENSES

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Approaches to Security

  • Prevention

– Stop an attack

  • Detection

– Detect an ongoing or past attack

  • Response

– Respond to attacks

  • The threat of a response may be enough to

deter some attackers

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SLIDE 35

Whole System is Critical

  • Securing a system involves a whole-system view

– Cryptography – Implementation – People – Physical security – Everything in between

  • This is because “security is only as strong as the

weakest link,” and security can fail in many places

– No reason to attack the strongest part of a system if you can walk right around it.

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Whole System is Critical

  • Securing a system involves a whole-system view

– Cryptography – Implementation – People – Physical security – Everything in between

  • This is because “security is only as strong as the

weakest link,” and security can fail in many places

– No reason to attack the strongest part of a system if you can walk right around it.

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SLIDE 37

Whole System is Critical

  • Securing a system involves a whole-system view

– Cryptography – Implementation – People – Physical security – Everything in between

  • This is because “security is only as strong as the

weakest link,” and security can fail in many places

– No reason to attack the strongest part of a system if you can walk right around it.

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SLIDE 38

Whole System is Critical

  • Securing a system involves a whole-system view

– Cryptography – Implementation – People – Physical security – Everything in between

  • This is because “security is only as strong as the

weakest link,” and security can fail in many places

– No reason to attack the strongest part of a system if you can walk right around it.

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