04/19/23NSF DG Workshop 2001, Privacy Panel

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Privacy and the digital citizen

Gene TsudikICS Dept, UC Irvine

www.ics.uci.edu/~gts

04/19/23NSF DG Workshop 2001, Privacy Panel

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Who? Why? What?

• Background– Research: applied crypto and

network/computer security– Anonymity and privacy in e-commerce– Anonymous communication (e.g., email,

mobile)– Group signatures (can be used for group

membership, petitions, voting, etc.)– Revocation of credentials and tight control

over security privileges

04/19/23NSF DG Workshop 2001, Privacy Panel

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04/19/23NSF DG Workshop 2001, Privacy Panel

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My current pet topics

• Secure e-Voting• Timestamping• Anonymous authentication• Hosting and manipulating

encrypted content

04/19/23NSF DG Workshop 2001, Privacy Panel

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Terminology:Privacy, Anonymity, etc.

• Not that closely related

• Privacy (passive) – I do nothing but want you to stay away from me and mine.

• Anonymity (active) – I do something (e.g., buy) and wish to keep my identity secret.

• Unlinkability (active) – I do something a number of times (anonymously) but don’t want you to “track” me.

04/19/23NSF DG Workshop 2001, Privacy Panel

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Example

• Voting: not private but anonymous and unlinkable– Must prove group membership

– Must make choices (submit vote) only once

– Vote must have integrity

– No one but I should know my vote or link my votes

– Must be able to verify that my vote counted – Should not be able to demonstrate my vote to others (else I

might sell it)

•

04/19/23NSF DG Workshop 2001, Privacy Panel

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One possible foundation for secure voting:Group Signatures

• Chaum and Van Heijst (1991)• Like a normal PK digital signature (more

structure)• Members and group manager (maybe distributed)• Anonymous, unlinkable signatures• Open possible but hard• Impersonation impossible• Phantom membership possible but avoidable• Revocation… a headache • Can be extended to support voting• MORE RESEARCH NEEDED!!!

04/19/23NSF DG Workshop 2001, Privacy Panel

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Secure and Reliable Time-stamping

• Need to prove possession of something (e.g., idea, manuscript, will) at a certain point in time

• Sequencing (causality)• Must be

– Public– Anonymous– Unlinkable– Oblivious to content (no censorship)

• Requires digital signatures and other tools• Currently (can be poorly) done via USPS and/or notary

public• MORE RESEARCH NEEDED!

04/19/23NSF DG Workshop 2001, Privacy Panel

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Authentication/Identification

Government bestows upon a citizen:• SSN• DL• Passport

04/19/23NSF DG Workshop 2001, Privacy Panel

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Why Anonymous Authentication

• Driver’s license is overloaded, overused, insecure

• SSN is overloaded, insecure• Usage of SSN’s for identification and

“authentication” is a national disgrace• Credit card numbers are trivial to

fabricate, steal, etc.• Bottomline: we trail as a country…

04/19/23NSF DG Workshop 2001, Privacy Panel

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What is AA? Example:

• Unique permanent ID embedded in a secure device

• One-time ephemeral ID displayed/produced upon each use

• PIN/PW- or possession-based authentication

• E.g., Social Security or Credit Card• One-time CC# isn’t worth stealing

04/19/23NSF DG Workshop 2001, Privacy Panel

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In conclusion:

What (I think) we need:

• Stop relying on SSNs and DLs for extraneous purposes

• Devise a national ID scheme (lunatic fringe notwithstanding)

• Promote one-time-id AA devices for credit/debit cards and other (perhaps only non-visual) forms of id

• For E-commerce, privacy QoS with consent: give up info get a $$ discount!