Transcript
Page 1: Accredited DomainKeys:    A Service Architecture for Improved Email Validation

Accredited DomainKeys: Accredited DomainKeys: A Service Architecture for A Service Architecture for Improved Email ValidationImproved Email Validation

Michael GoodrichMichael Goodrich Roberto TamassiaRoberto Tamassia Danfeng Yao Danfeng YaoUC Irvine UC Irvine Brown UniversityBrown University

Work principally supported by IAM RegistryWork principally supported by IAM RegistryAdditional funding from NSFAdditional funding from NSF

Page 2: Accredited DomainKeys:    A Service Architecture for Improved Email Validation

OverviewOverview

DomainKeys signs DomainKeys signs outgoing messages using public-key cryptography (Delany 04)– Did the sender actually send this email?

Accredited DomainKeys provides assurance of sender’s public key and evidence of sender domain’s trustworthiness– Is the sender of this email trustworthy?

Two approaches of implementing Accredited DomainKeys are presented

Page 3: Accredited DomainKeys:    A Service Architecture for Improved Email Validation

Send and Receive in DomainKeysSend and Receive in DomainKeys

Example.net Name Server

Example.net MTA

Yahoo.com MTA

Sign mail

Private key

Public keyQuery for public key

Verify signature

DomainKey-Signature: a=rsa-sha1; s=mail; d=example.net; c=simple; q=dns; b=Fg…5J

Out-going message

Authentication-Results: example.net [email protected]; domainkeys=pass;

In-coming message

Send signed email

Page 4: Accredited DomainKeys:    A Service Architecture for Improved Email Validation

Accredited DomainKeys Accredited DomainKeys ArchitectureArchitecture

Aims at establishing trust in the sender domain Aims at establishing trust in the sender domain – Scalability, efficiency, and usabilityScalability, efficiency, and usability

Extends DomainKeys frameworkExtends DomainKeys framework– Applicable also to Identified Internet Mail (Fenton, Applicable also to Identified Internet Mail (Fenton,

Thomas)Thomas)

Introduces a trusted third-party: Introduces a trusted third-party: accreditation accreditation bureaubureau– Accreditation bureau generates and updates Accreditation bureau generates and updates

accreditation sealsaccreditation seals for registered domains for registered domains– The accreditation seal is the proof of membershipThe accreditation seal is the proof of membership– Time quantum of seal updates depends on applicationsTime quantum of seal updates depends on applications

Page 5: Accredited DomainKeys:    A Service Architecture for Improved Email Validation

Send in Accredited DomainKeysSend in Accredited DomainKeys

Example.net Name Server

Example.net MTA

Bob

Write mail

Private key

Public key

Register public key Accreditation Bureau

Update seal at each time quantum

Accredited-DomainKeys: v=sealDomainKey-Signature: a=rsa-sha1; s=mail; d=example.net; c=simple; q=dns; b=Fg…5J

Yahoo.com MTA

Send signed email

Sign email

Page 6: Accredited DomainKeys:    A Service Architecture for Improved Email Validation

Receive in Accredited DomainKeysReceive in Accredited DomainKeys

Yahoo.com MTA

Query for public keyVerify signature

Query for accreditation sealVerify seal

Accreditation Bureau

Example.net Name Server

Update accreditation seal at each time quantum

Alice from Yahoo.com

Receive mail

Authentication-Results: example.net [email protected]; domainkeys=pass; accreditation=pass

Page 7: Accredited DomainKeys:    A Service Architecture for Improved Email Validation

Seal realization: simple signatureSeal realization: simple signature

The seal is a signature The seal is a signature signed by the bureau on signed by the bureau on the public key of a domainthe public key of a domain

The seal is refreshed at The seal is refreshed at each time quantumeach time quantum

The seal is verified The seal is verified against the public key of against the public key of the accreditation bureauthe accreditation bureau

Example.net Name Server

Accreditation Bureau

Update accreditation seal at each time quantum

Page 8: Accredited DomainKeys:    A Service Architecture for Improved Email Validation

Seal realization: STMSSeal realization: STMSThe Secure Transaction Management System The Secure Transaction Management System [Goodrich, Tamassia et al.] implements an [Goodrich, Tamassia et al.] implements an authenticated dictionaryauthenticated dictionary

Source

Responder A

Responder BDS

DS

DS

t

Basis (signed)Updates

User

Query

Response

AnswerProofBasis (signed)

t

Page 9: Accredited DomainKeys:    A Service Architecture for Improved Email Validation

Seal realization: STMS (cont’d)Seal realization: STMS (cont’d)Example.net Name Server (STMS Responder)

Accreditation Bureau (STMS Source)

Update proof and basis at each time quantum

Yahoo.com MTA (STMS User)

Query for accreditation seal (proof-basis pair) Verify signature

of basis

Verify proof of domain

Obtain the bureau’s public-key

Receive mail

Page 10: Accredited DomainKeys:    A Service Architecture for Improved Email Validation

Seal Realizations: EfficiencySeal Realizations: EfficiencyOperation Simple SignatureSimple Signature STMSSTMS

Accreditation Accreditation BureauBureau

Update seals of Update seals of MM domains domains

NN signatures signatures11 signature signature

1.5 1.5 MM log log NN hashes hashes

Receiver MTAReceiver MTA

Verify seals of Verify seals of DD domains domains

DD signature verifications signature verifications11 signature verification signature verification

1.5 1.5 DD log log NN hasheshashes

Sender Name Sender Name Server Server

Provide sealProvide seal 11 signature transmitted signature transmitted1 1 signature transmittedsignature transmitted

1.5 log 1.5 log NN hashes hashes transmittedtransmitted

N: Number of domains registered with the accreditation bureau

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Summary and Future WorkSummary and Future WorkSummarySummary– Accredited DK provides Accredited DK provides assurance of sender’s public key

and evidence of sender domain’s trustworthiness– Extension of DK frameworkExtension of DK framework– Accreditation seals issued by accreditation bureau and Accreditation seals issued by accreditation bureau and

stored in domain name serverstored in domain name server– STMS approach is more scalable than simple signature STMS approach is more scalable than simple signature

approachapproach

– Website:Website: http://www.accrediteddomainkeys.nethttp://www.accrediteddomainkeys.net

Current and Future Work Current and Future Work – Performance testsPerformance tests– Accredited DKIM Accredited DKIM

Page 12: Accredited DomainKeys:    A Service Architecture for Improved Email Validation

Related WorkRelated Work

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

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AcknowledgementsAcknowledgements

David Croston and IAM Registry, IncDavid Croston and IAM Registry, Inc

David Ellis, John Nuber

Eric Allman, Jon Callas, Mark Delany, and Jim Fenton

National Science Foundation


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