Accredited DomainKeys: A Service Architecture for Improved Email Validation

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Accredited DomainKeys: A Service Architecture for Improved Email Validation. Michael GoodrichRoberto Tamassia Danfeng Yao UC Irvine Brown University Work principally supported by IAM Registry Additional funding from NSF. Overview. - PowerPoint PPT Presentation

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  • Accredited DomainKeys: A Service Architecture for Improved Email ValidationMichael GoodrichRoberto Tamassia Danfeng YaoUC Irvine Brown University

    Work principally supported by IAM RegistryAdditional funding from NSF

  • OverviewDomainKeys signs outgoing messages using public-key cryptography (Delany 04)Did the sender actually send this email?Accredited DomainKeys provides assurance of senders public key and evidence of sender domains trustworthinessIs the sender of this email trustworthy?Two approaches of implementing Accredited DomainKeys are presented

  • Send and Receive in DomainKeysExample.net MTASign mailPrivate keyPublic keyVerify signature

  • Accredited DomainKeys ArchitectureAims at establishing trust in the sender domain Scalability, efficiency, and usabilityExtends DomainKeys frameworkApplicable also to Identified Internet Mail (Fenton, Thomas)Introduces a trusted third-party: accreditation bureauAccreditation bureau generates and updates accreditation seals for registered domainsThe accreditation seal is the proof of membershipTime quantum of seal updates depends on applications

  • Send in Accredited DomainKeysExample.net Name ServerPrivate keyPublic keySign email

  • Receive in Accredited DomainKeysVerify signatureVerify seal

  • Seal realization: simple signatureThe seal is a signature signed by the bureau on the public key of a domainThe seal is refreshed at each time quantumThe seal is verified against the public key of the accreditation bureauExample.net Name ServerAccreditation BureauUpdate accreditation seal at each time quantum

  • Seal realization: STMSThe Secure Transaction Management System [Goodrich, Tamassia et al.] implements an authenticated dictionarySourceResponder AResponder BDSDSDStBasis (signed)UpdatesUserAnswerProofBasis (signed)t

  • Seal realization: STMS (contd)Update proof and basis at each time quantumQuery for accreditation seal (proof-basis pair) Verify signature of basis

    Verify proof of domainObtain the bureaus public-key

  • Seal Realizations: EfficiencyN: Number of domains registered with the accreditation bureau

  • Summary and Future WorkSummaryAccredited DK provides assurance of senders public key and evidence of sender domains trustworthinessExtension of DK frameworkAccreditation seals issued by accreditation bureau and stored in domain name serverSTMS approach is more scalable than simple signature approachWebsite: http://www.accrediteddomainkeys.netCurrent and Future Work Performance testsAccredited DKIM

  • Related WorkSPF (Lentczner, Wong) and Sender ID Framework (Microsoft)DomainKeys (Delany)Identified Internet Mail (Fenton, Thomas)Flexible Sender Validation (Levine)Sender Authorization with RMX DNS RR (Danisch)Reverse DNS Marking (Stumpf, Hoehne)Project Lumos (Email Service Provider Coalition)Authenticated data structures (Goodrich, Tamassia et al.)

  • AcknowledgementsDavid Croston and IAM Registry, IncDavid Ellis, John NuberEric Allman, Jon Callas, Mark Delany, and Jim FentonNational Science Foundation

    Proposed by Delany in 2004Similar to Identified Mail by Fenton and ThomasAims to prevent domain spoofing in emailFor authentication of sender domainSender domain signs emails with its private keyReceiver MTA verifies the signatureStores the public key of a domain on its name serverIn a TXT record under _domainkey sub-namespace (e.g. mail._domainkey.example.net

    HeadersMeaning of the signatureVoucher the sender domain is authorizedFor the receiver mta to establish trust with sender domainKey value pairsShow the message of accredited DK

    Why there are multiple respondersResponder does not sign

    Basis300/16 = 202log_2 N = 20N= th

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