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Transparency Overlays and Applications Melissa Chase (Microsoft - - PowerPoint PPT Presentation

Mar 23, 2024 108 likes •1.32k views

Transparency Overlays and Applications Melissa Chase (Microsoft Research Redmond) Sarah Meiklejohn (University College London) 2 (icons by parkjisun from noun project) 2 (icons by parkjisun from noun project) 2 (icons by parkjisun from noun

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Transparency Overlays and Applications

Melissa Chase (Microsoft Research Redmond) Sarah Meiklejohn (University College London)

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(icons by parkjisun from noun project)

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? ? ? ?

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(icons by parkjisun from noun project)

advertisers doctors spy agencies credit raters marketers insurance companies hackers

? ? ? ? ? ? ? ?

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events in the system can be

  • data access by user
  • data access by third party
  • data creation by user
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events in the system can be

  • data access by user
  • data access by third party
  • data creation by user

transparency: bad events are exposed

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

a transparency overlay

(architecture very much inspired by Certificate Transparency [LL’13])

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence design

a transparency overlay

(architecture very much inspired by Certificate Transparency [LL’13])

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4

system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence design security

a transparency overlay

(architecture very much inspired by Certificate Transparency [LL’13])

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence design security

a transparency overlay

(architecture very much inspired by Certificate Transparency [LL’13]) construction

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence design security which systems?

a transparency overlay

(architecture very much inspired by Certificate Transparency [LL’13]) construction

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4

system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence design security which systems?

a transparency overlay

design (architecture very much inspired by Certificate Transparency [LL’13]) construction

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system

design

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system log server

log

log server

log

log server

log

log server

log

design

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5

system log server

log

design

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5

system GenEventSet log server

log

design

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5

system Log GenEventSet log server

log

design

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auditors (efficiently) determine if events are in the log

system Log CheckEntry GenEventSet (meaning |snap| ≪ |log|) auditor snap log server

log

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monitors (inefficiently) detect bad events in the log

system Log CheckEntry GenEventSet Inspect log server

log

auditor snap monitor

snap BE E

(meaning |E| ≈ |log|)

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auditors and monitors ensure consistent view of log

system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence (can output evidence of inconsistencies)

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence design security which systems? (add LS,Au,Mo) design construction

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence design security which systems? security (add LS,Au,Mo) construction

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system Log CheckEntry GenEventSet Inspect Gossip evidence

consistency

log server

log

monitor

snap BE E

auditor snap CheckEvidence

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CheckEntry Inspect Gossip evidence

consistency

monitor

snap BE E

auditor snap CheckEvidence

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CheckEntry Inspect Gossip evidence

consistency

adversary wins if (1) evidence fails even though (2) monitor and auditor did have inconsistent view there exists event that auditor thinks is in the log but monitor doesn’t monitor

snap BE E

auditor snap CheckEvidence

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system Log CheckEntry GenEventSet Inspect Gossip evidence

non-frameability (related to [DGHS’16])

log server

log

monitor

snap BE E

auditor snap CheckEvidence

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Log CheckEntry Inspect evidence

non-frameability (related to [DGHS’16])

adversary wins if evidence passes log server

log

CheckEvidence

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system Log CheckEntry GenEventSet Inspect Gossip evidence

accountability

log server

log

monitor

snap BE E

auditor snap CheckEvidence

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system Log CheckEntry GenEventSet Inspect Gossip evidence

accountability

adversary wins if (1) it promised to include an event that (2) auditor and monitor believe to not be in the log, but (3) evidence fails monitor

snap BE E

auditor snap CheckEvidence

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence design security construction which systems? security (add LS,Au,Mo) (consistency) (non-frameability) (accountability)

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence design security construction which systems? (add LS,Au,Mo) (consistency) (non-frameability) construction (accountability)

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dynamic list commitment (dlc)

(aka tamper-evident log [CW’09]) (aka authenticated data structure [AGT’01,PSTY’13]) (aka rolling hash chain or Merkle tree [M’89])

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dynamic list commitment (dlc)

system

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dynamic list commitment (dlc)

system

e1 e2

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dynamic list commitment (dlc)

Com CheckCom Append basic

system

e1 e2

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dynamic list commitment (dlc)

Com CheckCom Append basic

system (generate succinct commitment)

e1 e2

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dynamic list commitment (dlc)

Com CheckCom Append basic

system (generate succinct commitment) (check commitment)

e1 e2

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dynamic list commitment (dlc)

Com CheckCom Append basic

e1 e2 e3 e4

system (generate succinct commitment) (check commitment) (add new events)

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dynamic list commitment (dlc)

Com CheckCom Append ProveAppend CheckAppend basic all events?

system

e1 e2

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dynamic list commitment (dlc)

Com CheckCom Append ProveAppend CheckAppend basic all events?

e1 e2 e3 e4

system (can’t delete events)

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dynamic list commitment (dlc)

Com CheckCom Append ProveAppend CheckAppend ProveIncl CheckIncl basic all events? specific event?

e1 e2 e3 e4

system (can’t omit events)

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dynamic list commitment (dlc)

Com CheckCom Append ProveAppend CheckAppend ProveIncl CheckIncl basic all events? specific event?

system

e1 e2 e3 e4

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dynamic list commitment (dlc)

Com CheckCom Append ProveAppend CheckAppend ProveIncl CheckIncl basic all events? specific event?

system

e1 e2 e3 e4

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dynamic list commitment (dlc)

Com CheckCom Append ProveAppend CheckAppend ProveIncl CheckIncl basic all events? specific event?

system

e1 e2 e3 e4

this is ordered w.r.t. some notion of time

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dynamic list commitment (dlc)

Com CheckCom Append ProveAppend CheckAppend ProveIncl CheckIncl basic all events? specific event? DemoInconsistent CheckInconsistent inconsistent?

“your commitment c does not represent the state of my list at time t” system

e1 e2 e3 e4

this is ordered w.r.t. some notion of time

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dynamic list commitment (dlc)

Com CheckCom Append ProveAppend CheckAppend ProveIncl CheckIncl basic all events? specific event? DemoInconsistent CheckInconsistent inconsistent? DemoNotIncl CheckNotIncl non-inclusion?

“your commitment c does not represent the state of my list at time t” system

e1 e2 e3 e4

this is ordered w.r.t. some notion of time

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system Log CheckEntry GenEventSet Inspect Gossip evidence

construction

log server

log

monitor

snap BE E

auditor snap CheckEvidence

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system Log CheckEntry GenEventSet Inspect Gossip evidence

construction

log server

log

monitor

snap BE E

auditor snap CheckEvidence

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system Log CheckEntry GenEventSet Inspect Gossip evidence

construction

log server

log

monitor

snap BE E

auditor snap CheckEvidence

dlc snap t sig

=

a (timed) signature, so no one can frame LS

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system Log CheckEntry GenEventSet Inspect Gossip evidence

construction

log server

log

monitor

snap BE E

auditor snap CheckEvidence

dlc snap t sig

=

snap E log =

a (timed) signature, so no one can frame LS

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= Sys LS

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= Sys LS

event

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= Sys LS

event rcpt a (timed) signature, so LS is accountable

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= Sys LS

event rcpt check rcpt a (timed) signature, so LS is accountable

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= Sys LS

event rcpt update log

  • add event to E
  • update dlc
  • update snap

check rcpt a (timed) signature, so LS is accountable

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= LS Sys Auditor

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= LS Sys Auditor

event

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= LS Sys Auditor

event update?

LS Auditor

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= LS Sys Auditor

event update?

LS Auditor

snapA

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= LS Sys Auditor

event update?

LS Auditor

snapA ProveAppend

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= LS Sys Auditor

event update?

LS Auditor

snapA ProveAppend snapLS,π

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= LS Sys Auditor

event update?

LS Auditor

snapA ProveAppend CheckAppend snapLS,π

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= LS Sys Auditor

event update?

LS Auditor

snapA ProveAppend CheckAppend snapLS,π event

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= LS Sys Auditor

event update?

LS Auditor

snapA ProveAppend CheckAppend snapLS,π event ProveIncl

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= LS Sys Auditor

event update?

LS Auditor

snapA ProveAppend CheckAppend snapLS,π event ProveIncl CheckIncl

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= LS Sys Auditor

event update?

LS Auditor

snapA ProveAppend CheckAppend snapLS,π event ProveIncl CheckIncl b

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= LS Monitor

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= LS Monitor

snapM

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= LS Monitor

snapM find EΔ (events since snapM)

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= LS Monitor

snapM find EΔ (events since snapM) snapLS,EΔ

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= LS Monitor

snapM find EΔ (events since snapM) snapLS,EΔ Append(EΔ,dlcM) = dlcLS? use checks to update BE

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= Monitor Auditor

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= Monitor Auditor

snapM,snapA

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= Monitor Auditor

snapM,snapA DemoInconsistent(E,dlcA,tA) π

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= Monitor Auditor

snapM,snapA DemoInconsistent(E,dlcA,tA) π b←CheckInconsistent(dlcA,tA,dlcM,π) if b return (snapA,snapM,π)

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

snap E log = dlc snap t sig

= Monitor Auditor

snapM,snapA DemoInconsistent(E,dlcA,tA) π b←CheckInconsistent(dlcA,tA,dlcM,π) if b return (snapA,snapM,π) checks that (1) snapshots are signed by LS and (2) π proves inconsistency

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security

ability to carry out DemoInconsistent, ProveAppend, and ProveIncl ⇒ consistency unforgeability of DemoInconsistent, DemoNotIncl*, and signature scheme ⇒ non-frameability ability to carry out DemoNotIncl* ⇒ accountability

*uses pledged version in which Auditor keeps track of failed events and gossips about them with Monitor to produce new type of evidence

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goal: bad events are exposed

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goal: bad events are exposed system receives promises to include events in the log

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+ auditors determine if these events are in the log

auditor system CheckEntry log server

goal: bad events are exposed system receives promises to include events in the log

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+ auditors determine if these events are in the log + auditors and monitors ensure consistent view of log

monitor auditor Gossip auditor system CheckEntry log server

goal: bad events are exposed system receives promises to include events in the log

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+ auditors determine if these events are in the log + auditors and monitors ensure consistent view of log ⇒ (by consistency+accountability) event is in monitor’s view of the log

monitor auditor Gossip auditor system CheckEntry log server

goal: bad events are exposed system receives promises to include events in the log

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+ auditors determine if these events are in the log + auditors and monitors ensure consistent view of log ⇒ (by consistency+accountability) event is in monitor’s view of the log

monitor auditor Gossip

+ monitors detect bad events in the log ⇒

auditor system CheckEntry log server

goal: bad events are exposed system receives promises to include events in the log

log server monitor Inspect

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence design security which systems? (add LS,Au,Mo) (consistency) (non-frameability) (dlc+sig) construction construction (accountability)

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence design security which systems? (add LS,Au,Mo) (consistency) (non-frameability) (dlc+sig) which systems? construction (accountability)

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Log CheckEntry Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

Certificate Transparency

CA client website

bad certificate issuance is exposed ⇒ clients are less likely to accept bad certificates

(icon by parkjisun from noun project)

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Log CheckEntry Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

Bitcoin

sender receiver miner blockchain

double spending is exposed

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Log CheckEntry Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

Bitcoin

sender receiver miner blockchain

double spending is exposed … provably!

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Log CheckEntry Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

Bitcoin

sender receiver miner blockchain

double spending is exposed … provably! sender and receiver don’t need to store blockchain

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Log CheckEntry Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence

Bitcoin

sender receiver miner blockchain

double spending is exposed … provably! sender and receiver don’t need to store blockchain gives rise to hybrid system with no mining

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence design security which systems? (add LS,Au,Mo) (consistency) (non-frameability)

  • pen problems

(dlc+sig) construction (accountability) (CT+Bitcoin)

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence design security which systems? (add LS,Au,Mo) (consistency) (non-frameability) all parties needed?

  • pen problems

(dlc+sig) construction (accountability) (CT+Bitcoin)

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence design security which systems? (add LS,Au,Mo) (consistency) (non-frameability) all parties needed? privacy?

  • pen problems

(dlc+sig) construction (accountability) (CT+Bitcoin)

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence design security which systems? (add LS,Au,Mo) (consistency) (non-frameability) all parties needed? privacy? better?

  • pen problems

(dlc+sig) construction (accountability) (CT+Bitcoin)

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence design security which systems? (add LS,Au,Mo) (consistency) (non-frameability) all parties needed? privacy?

  • thers?

better?

  • pen problems

(dlc+sig) construction (accountability) (CT+Bitcoin)

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system Log CheckEntry GenEventSet Inspect Gossip evidence log server

log

monitor

snap BE E

auditor snap CheckEvidence design security which systems? (add LS,Au,Mo) (consistency) (non-frameability) all parties needed? privacy?

  • thers?

better?

Thanks for listening! Full version: eprint.iacr.org/2016/915

  • pen problems

(dlc+sig) construction (accountability) (CT+Bitcoin)

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dynamic list commitment (dlc)

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dynamic list commitment (dlc)

Com CheckCom Append basic

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dynamic list commitment (dlc)

Com

e1 e2

CheckCom Append basic

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dynamic list commitment (dlc)

Com

e1 e2

CheckCom Append

Com( ) = H(e2||H(e1))

e1 e2

basic

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dynamic list commitment (dlc)

Com

e1 e2

CheckCom Append

Com( ) = H(e2||H(e1))

e1 e2

CheckCom(c, ) = (c = H(e2||H(e1)))

e1 e2

basic

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dynamic list commitment (dlc)

Com

e1 e2

CheckCom Append

Append( ,c12) = H(e4||(H(e3)||c12))

e3 e4

Com( ) = H(e2||H(e1))

e1 e2

CheckCom(c, ) = (c = H(e2||H(e1)))

e1 e2

basic

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dynamic list commitment (dlc)

Com

e1 e2

CheckCom Append

Append( ,c12) = H(e4||(H(e3)||c12))

e3 e4 e1 e2 e3 e4

Com( ) = H(e2||H(e1))

e1 e2

CheckCom(c, ) = (c = H(e2||H(e1)))

e1 e2

basic

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dynamic list commitment (dlc)

Com

e1 e2

CheckCom Append

Append( ,c12) = H(e4||(H(e3)||c12))

e3 e4

ProveAppend CheckAppend

e1 e2 e3 e4

Com( ) = H(e2||H(e1))

e1 e2

CheckCom(c, ) = (c = H(e2||H(e1)))

e1 e2

basic all events?

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dynamic list commitment (dlc)

Com

e1 e2

CheckCom Append

Append( ,c12) = H(e4||(H(e3)||c12))

e3 e4

ProveAppend CheckAppend

e1 e2 e3 e4

Com( ) = H(e2||H(e1))

e1 e2

CheckCom(c, ) = (c = H(e2||H(e1)))

e1 e2

ProveAppend(c12,c1234, ) = e3 e4

e1 e2 e3 e4

basic all events?

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dynamic list commitment (dlc)

Com

e1 e2

CheckCom Append

Append( ,c12) = H(e4||(H(e3)||c12))

e3 e4

ProveAppend CheckAppend

e1 e2 e3 e4

CheckAppend(c12,c1234, ) = (c1234 = Append( ,c12))

e3 e4 e3 e4

Com( ) = H(e2||H(e1))

e1 e2

CheckCom(c, ) = (c = H(e2||H(e1)))

e1 e2

ProveAppend(c12,c1234, ) = e3 e4

e1 e2 e3 e4

basic all events?

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dynamic list commitment (dlc)

Com

e1 e2

CheckCom Append

Append( ,c12) = H(e4||(H(e3)||c12))

e3 e4

ProveAppend CheckAppend ProveIncl CheckIncl

e1 e2 e3 e4

CheckAppend(c12,c1234, ) = (c1234 = Append( ,c12))

e3 e4 e3 e4

Com( ) = H(e2||H(e1))

e1 e2

CheckCom(c, ) = (c = H(e2||H(e1)))

e1 e2

ProveAppend(c12,c1234, ) = e3 e4

e1 e2 e3 e4

basic all events? specific event?

slide-119
SLIDE 119

30

dynamic list commitment (dlc)

Com

e1 e2

CheckCom Append

Append( ,c12) = H(e4||(H(e3)||c12))

e3 e4

ProveAppend CheckAppend ProveIncl CheckIncl

e1 e2 e3 e4

CheckAppend(c12,c1234, ) = (c1234 = Append( ,c12))

e3 e4 e3 e4

Com( ) = H(e2||H(e1))

e1 e2

CheckCom(c, ) = (c = H(e2||H(e1)))

e1 e2

ProveAppend(c12,c1234, ) = e3 e4

e1 e2 e3 e4

ProveIncl(c1234,e3, ) = (c12, )

e1 e2 e3 e4 e4

basic all events? specific event?

slide-120
SLIDE 120

30

dynamic list commitment (dlc)

Com

e1 e2

CheckCom Append

Append( ,c12) = H(e4||(H(e3)||c12))

e3 e4

ProveAppend CheckAppend ProveIncl CheckIncl

e1 e2 e3 e4

CheckAppend(c12,c1234, ) = (c1234 = Append( ,c12))

e3 e4 e3 e4

Com( ) = H(e2||H(e1))

e1 e2

CheckCom(c, ) = (c = H(e2||H(e1)))

e1 e2

ProveAppend(c12,c1234, ) = e3 e4

e1 e2 e3 e4

ProveIncl(c1234,e3, ) = (c12, )

e1 e2 e3 e4 e4

CheckIncl(c1234,e3,(c12, )) = CheckAppend(c12,c1234, )

e4 e3 e4

basic all events? specific event?