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privacy preserving e-petitions

This paper explores the implementation of privacy-preserving e-petitions, combining anonymous credentials and existing technologies, to ensure signer anonymity and verifiability without compromising security. The architecture addresses the challenges of authentication, authorization, integrity, confidentiality, multiple signing prevention, and signer anonymity.

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privacy preserving e-petitions

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  1. privacy preserving e-petitions Claudia Diaz, HanneloreDekeyser, MarkulfKohlweiss, GirmaNigusse K.U.Leuven IDIS Workshop 29/05/2008 [Work done in the context of the ADAPID project]

  2. ADAPID • Advanced applications for e-ID cards • Basic Research project funded by IWT • Focus on security and privacy • Belgian e-ID based on PKI with X509 certificates • Hard to build privacy friendly applications • E-Government • Hard to find applications where anonymity is arguably necessary

  3. Petitions in the physical world • Formal request addressed to an authority and signed by numerous individuals • Typically citizens provide • Unique identifier (name, national ID number) • Signature • Verification: • Validating that the signatures correspond to the identifiers • Discarding multiple/invalid signatures

  4. Electronic petitions • Benefits of going electronic: • Many resources are needed in order to physically collect the signatures • Manual signature verification is a costly and tedious process • Drawbacks • Easy to cheat (e.g., knowledge of other people’s name and ID number) • Countermeasures may “disenfranchise” petition signers (e.g., IP detection) • Good example of ICT enabling participatory e-democracy

  5. The naive e-petition implementation • Have users sign the petitions with their e-ID • Select petition • Sign using the e-ID (2-factor authentication) • Validate signature and check that the petition has not yet been signed with that e-ID • Count (or discard) the signature • Privacy risks • Leak sensitive information on political beliefs, religious inclinations, etc. (this may prevent some people from signing) • Through unique identifiers, petition signatures can be linked to other data

  6. e-petition requirements • Basic requirements • Authentication: citizen is who claims to be (i.e., no impersonation) • Authorization: citizen is entitled to sign (e.g., age > 18) • Integrity, Confidentiality • Multiple signing prevention • Verifiability: all valid signatures are counted • Privacy requirements • Signer anonymity: citizen unlinkable to petition (i.e., not possible to identify who are the signers)

  7. Anonymouscredentialprotocols • Active area of research in cryptography • Theyrely on cryptographicprotocols and Zero-Knowlegeproofs to reduce to the bare minimum the amount of information disclosed • Flexible protocols, many options possible • Example: • CI issues a credential to U that encodes U’sage • U canprove to V thathisageisabove/below a threshold • V can check thatthisiscertified by CI • V does not learnU’s exact age

  8. PKI vsanonymous credentials PKI Anonymous credentials • Signed by a trusted issuer • Certification of attributes • Authentication (secret key) • Double-signing detection • No data minimization • Users are identifiable • Users can be tracked (Signature linkable to other contexts where e-ID is used) • Signed by a trusted issuer • Certification of attributes • Authentication (secret key) • Double-signing detection • Data minimization • Users are anonymous • Users are unlinkable in different contexts

  9. Architecture

  10. Properties • Only citizens entitled to sign can do so • Possession of e-ID + knowledge of PIN • Attribute verification (e.g., age, locality) • One credential per citizen • Citizens can sign only once (multiple signing is detectable so that repeated signatures can be deleted) • Collusion of credential issuer and e-Petition server does not reveal the identity of a signer • Verifiability through publishing the protocol transcripts

  11. Summary and conclusions • Summary of the paper • Motivation for privacy preserving e-petitions • Requirement study • Introduction to anonymous credentials • Architectural design combining existing technologies • Legal issues • To be added: details of the protocols and implementation • Proof-of-concept • We can satisfy seemingly contradictory requirements • Security properties can be achieved without identifiability • National ID can be user to bootstrap privacy friendlier IDM, while preventing Sybil attacks

  12. Thankyou!

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