PRIVACY AND ANONYMITY Lecture 11 - Computer Science€¦ · PRIVACY AND ANONYMITY Lecture 11...

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Muhammad Rizwan Asghar August 14, 2019 PRIVACY AND ANONYMITY Lecture 11 COMPSCI 316 Cyber Security Source of most slides: Northeastern University, USA
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Transcript of PRIVACY AND ANONYMITY Lecture 11 - Computer Science€¦ · PRIVACY AND ANONYMITY Lecture 11...

  • Slide title

    In CAPITALS

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    Slide subtitle

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    Muhammad Rizwan Asghar

    August 14, 2019

    PRIVACY AND ANONYMITY

    Lecture 11

    COMPSCI 316

    Cyber Security

    Source of most slides: Northeastern University, USA

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    FOCUS OF THIS LECTURE

    Understand privacy and anonymity

    Discuss solutions that offer privacy and

    anonymity

    Learn attacks on privacy and anonymity

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    MOTIVATION FOR PRIVACY

    People have the right to keep their personal

    data private

    – Right to privacy

    Privacy also means not to reveal information

    about who is communicating with whom

    The use of online services can pose a threat to

    our privacy!

    – There is a possibility to link users’ actions

    https://www.securitymagazine.com/articles/89444-the-importance-of-cybersecurity-in-modern-video-surveillance-environments

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    MOTIVATION FOR ANONYMITY

    Hiding identities of communicating parties from

    each other or from third parties

    Anonymity is a tool to preserve privacy

    For many applications, a user identity might

    not be needed by the service provider

    – E.g., web browsing

    https://www.tusacentral.net/joomla/index.php/marcos-talks/165-open-letter-to-anonymous.html

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    USE OF ANONYMITY

    Free speech for political and other comments

    Whistleblowers

    Journalists

    Human rights activists

    Normal users for avoiding tracking

    https://www.maxpixel.net/Correct-Okay-Mark-Right-Green-Sign-Symbol-Ticks-39830

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    ABUSE OF ANONYMITY

    Disclosure of trade secrets

    DoS

    Other illegal activities by cybercriminals

    – Illegal downloads

    E.g., copyright infringement

    – Scams

    – Hacking

    https://steamcommunity.com/sharedfiles/filedetails/?id=1380395113

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    ARE YOU ANONYMOUS

    Your IP address can be linked directly to you

    – ISPs store communications record

    – Data retention laws

    You are being tracked

    – Cookies

    – Browser fingerprinting

    – Device fingerprinting

    https://www.eventbrite.com/blog/custom-questions-event-attendees-ds0c/

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    QUANTIFYING ANONYMITY

    How can we calculate how anonymous we

    are?

    Who sent this

    message?

    Suspects (Anonymity Set)

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    QUANTIFYING ANONYMITY

    A larger anonymity set means stronger

    anonymity

    Source: pixabay.com

    https://pixabay.com/photos/lego-figurines-toys-crowd-many-1044891

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    SOME TERMS

    Unlinkability

    – The inability of linking two or more items of

    interest

    E.g., packets, events, people, actions, etc.

    – Three aspects

    Sender anonymity: who sent?

    Receiver anonymity: who is the destination?

    Relationship anonymity: who communicates with

    whom?

    Unobservability

    – The items of interest are indistinguishable from all

    other items

    https://www.jonesmedical.com/spirometry-terminology/

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    PUBLIC KEY CRYPTO: REVISIT

    Safe to distribute the public key KP– Can only decrypt with the private key KS– Computationally infeasible to derive KS from KP

    KP

    KP

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    ENCRYPTED DATA TRAFFIC

    Content is unobservable

    – Due to encryption

    Source and destination are

    trivially linkable

    – No anonymity

    Data Traffic

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    ANONYMISING PROXIES

    Proxy Server

    Using trusted centralised servers

    Hides IP address of users

    Users are not anonymous to proxy servers

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    ANONYMISING PROXIES:

    SENDER ANONYMITY

    Proxy Server

    Source is unknown

    Destination is known

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    ANONYMISING PROXIES:

    RECEIVER ANONYMITY

    Proxy Server

    Source is known

    Destination is unknown

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    ANONYMISING PROXIES:

    MALICIOUS PROXY SERVER

    Proxy Server

    No anonymity

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    ANONYMISING PROXIES:

    TRAFFIC ANALYSIS

    Proxy Server

    Statistical analysis of traffic patterns can compromise

    anonymity, i.e., timing and/or volume of packets

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    SAMPLE QUESTION

    Which one of the following statements is FALSE?

    a) Data encryption provides unobservability

    b) Anonymous proxy offers unlinkability

    c) Both a & b

    d) Data encryption guarantees anonymity

    https://pxhere.com/en/photo/1586349

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    SAMPLE QUESTION: ANSWER

    Which one of the following statements is FALSE?

    a) Data encryption provides unobservability

    b) Anonymous proxy offers unlinkability

    c) Both a & b

    d) Data encryption guarantees anonymity

    Answer) d

    https://pxhere.com/en/photo/1586349

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    DATA TO PROTECT

    Personally Identifiable Information (PII)

    – Name, address, phone number, etc.

    OS and browser information

    – Cookies

    IP address

    Amount of data sent and received

    Traffic timing

    https://www.greentechmedia.com/articles/read/california-utilities-on-data-sharing-yes-no-and-lets-talk-about-it

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    MIX NETWORKS

    Use a chain of anonymous proxies

    Each proxy is known as a Mix

    A mix receives messages from a set of

    senders, shuffle them, and send to another mix

    Originally designed for anonymous email

    https://wombat.factcenter.org/how-to-vote/the-tallying-process

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    MIX PROXIES AND ONION ROUTING

    Mixes form a cascade of anonymous proxies

    Traffic is protected with layers of encryption

    Mix

    [KP , KP , KP]

    Encrypted

    Tunnels

    Non-encrypted

    data

    E(KP , E(KP , E(KP , M))) = C

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    ENCRYPTED PATH: ANOTHER VIEW

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    RETURN TRAFFIC

    In a mix network, how can the destination respond to

    the sender?

    During path establishment, the sender places keys at

    each mix along the path

    – Data is re-encrypted as it travels the reverse path

    KP1 KP2 KP3

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    TO BE CONTINUED

    See the next lecture

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    Questions?

    Thanks for your attention!