Byzantine Fault Tolerant Public Key Authentication in Peer-to-peer Systems
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Transcript of Byzantine Fault Tolerant Public Key Authentication in Peer-to-peer Systems
Byzantine Fault Tolerant Byzantine Fault Tolerant Public Key Authentication Public Key Authentication in Peer-to-peer Systemsin Peer-to-peer Systems
Vivek Pathak and Liviu IftodeVivek Pathak and Liviu IftodeDepartment of Computer ScienceDepartment of Computer Science
Rutgers UniversityRutgers University
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OutlineOutline IntroductionIntroduction
Public key authenticationPublic key authentication Existing modelsExisting models
Motivation for Peer-to-peer authenticationMotivation for Peer-to-peer authentication Other solutions Other solutions
Byzantine fault tolerant authentication Byzantine fault tolerant authentication Security modelSecurity model Outline of correctness and performanceOutline of correctness and performance
Future workFuture work
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Public Key EncryptionPublic Key Encryption Public-private key pairPublic-private key pair Bootstrap shared secret encryptionBootstrap shared secret encryption Validation of digital signatureValidation of digital signature
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Authentication of Public Authentication of Public KeysKeys
Mapping identities to public keysMapping identities to public keys Trusted third parties (TTP)Trusted third parties (TTP)
Certificate authority (CA)Certificate authority (CA) Web of trust Web of trust
PGPPGP
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Authentication through CAAuthentication through CA Provide public key certificateProvide public key certificate
Use secure channel for bootstrapping Use secure channel for bootstrapping
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Authentication through CAAuthentication through CA
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Authentication through CAAuthentication through CA Represent centralized aggregation of trustRepresent centralized aggregation of trust
Long lived CA keysLong lived CA keys Single point of failureSingle point of failure
Public key revocation Public key revocation Scalability with number of certified keysScalability with number of certified keys
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Web of TrustWeb of Trust Informal human authenticationInformal human authentication
PGP key ringsPGP key rings Levels of trustLevels of trust
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Web of TrustWeb of Trust Peers take on the role of CAPeers take on the role of CA Decentralized trustDecentralized trust
No single point of failure No single point of failure Key authentication depends on human Key authentication depends on human
connectionsconnections How to apply to autonomous systemsHow to apply to autonomous systems
Sophisticated usersSophisticated users
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OutlineOutline IntroductionIntroduction
Public key authenticationPublic key authentication Existing modelsExisting models
Motivation for Peer-to-peer authenticationMotivation for Peer-to-peer authentication Other solutions Other solutions
Byzantine fault tolerant authentication Byzantine fault tolerant authentication Security modelSecurity model Outline of correctness and performanceOutline of correctness and performance
Future workFuture work
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Characteristics of Peer-to-peer Characteristics of Peer-to-peer SystemsSystems
Heterogeneous peers Heterogeneous peers Lack of trusted third partiesLack of trusted third parties Hierarchical Certificate AuthoritiesHierarchical Certificate Authorities
Large scale peer-to-peer systemsLarge scale peer-to-peer systems Need decentralized solutionNeed decentralized solution Administrative burden on CA Administrative burden on CA Scalability of key revocation Scalability of key revocation
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Characteristics of Peer-to-peer Characteristics of Peer-to-peer SystemsSystems
Autonomous operationAutonomous operation Unsophisticated usersUnsophisticated users Sensors and devicesSensors and devices Web of trust depends on constant human Web of trust depends on constant human
feedbackfeedback Short lived public keysShort lived public keys
Peers may be attacked and recoverPeers may be attacked and recover Public key certificates require secure channelPublic key certificates require secure channel
Malicious peersMalicious peers
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Other SolutionsOther Solutions Threshold encryption systemsThreshold encryption systems
Share the secret among a set of partiesShare the secret among a set of parties Defend against a few compromised partiesDefend against a few compromised parties
Secure initialization phaseSecure initialization phase Crypto based network IDsCrypto based network IDs
Choose network ID as function of public keyChoose network ID as function of public key Depends on the routing infrastructureDepends on the routing infrastructure
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OutlineOutline IntroductionIntroduction
Public key authenticationPublic key authentication Existing modelsExisting models
Motivation for Peer-to-peer authenticationMotivation for Peer-to-peer authentication Other solutions Other solutions
Byzantine fault tolerant authentication Byzantine fault tolerant authentication Security modelSecurity model Outline of correctness and performanceOutline of correctness and performance
Future workFuture work
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System ModelSystem Model Mutually authenticating peersMutually authenticating peers
Associate network end-point to Associate network end-point to public keypublic key
Asynchronous networkAsynchronous network No partitioning No partitioning Eventual delivery after Eventual delivery after
retransmissionsretransmissions Disjoint message transmission Disjoint message transmission
pathspaths Man-in-the-middle attack on Ø Man-in-the-middle attack on Ø
fraction of peersfraction of peers
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Attack ModelAttack Model Malicious peersMalicious peers
Honest majority Honest majority At most At most tt of the of the nn peers are faulty or malicious peers are faulty or malicious
peers where peers where tt = = 1-6Ø1-6Ø//3 3 nn Passive adversariesPassive adversaries Active adversariesActive adversaries
Relax network-is-the-adversary modelRelax network-is-the-adversary model Unlimited spoofingUnlimited spoofing Limited power to prevent message deliveryLimited power to prevent message delivery
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Authentication ModelAuthentication Model Challenge-response protocolChallenge-response protocol
No active attacksNo active attacks Man in the middle attackMan in the middle attack
Limited number of attacksLimited number of attacks
Proof of possession of KProof of possession of Kaa
{b,a,Challenge,K{b,a,Challenge,Kaa(r)}(r)}b b , {a,b,Response,r}, {a,b,Response,r}aa
B AKA
KA(NB)
NB
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Authentication ModelAuthentication Model Distributed AuthenticationDistributed Authentication
Challenge response from multiple peers Challenge response from multiple peers Gather proofs of possessionGather proofs of possession
Lack of consensus on authenticityLack of consensus on authenticity Malicious peersMalicious peers Man-in-the-middle attackMan-in-the-middle attack
C
A
D
B
FE
C
A
D
B
FE
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Authentication CorrectnessAuthentication Correctness Validity of proofs of possessionValidity of proofs of possession
{e,a,Challenge,K{e,a,Challenge,Kaa(r)}(r)}e e , {a,e,Response,r}, {a,e,Response,r}aa
All messages are signedAll messages are signed Required for proving malicious behavior Required for proving malicious behavior Recent proofs stored by the peersRecent proofs stored by the peers
C
A
D
B
FEFrom peersFrom peers PPBB PPCC PPDD PPEE PPFF
From AFrom A PPBB PPCC PPDD PPEE PPFF
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Byzantine Agreement Byzantine Agreement OverviewOverview
Publicize lack of consensusPublicize lack of consensus Authenticating peer sends proofs of Authenticating peer sends proofs of
possession to peerspossession to peers Each peer tries to authenticate AEach peer tries to authenticate A
Sends its proof-of-possession vector Sends its proof-of-possession vector to every peerto every peer
Byzantine agreement on Byzantine agreement on authenticity of Kauthenticity of KAA
Majority decision at every peerMajority decision at every peer Identify malicious peersIdentify malicious peers Complete authenticationComplete authentication
From BFrom B 11 11 00 11 11
From CFrom C 11 11 11 11 11
From DFrom D 11 11 11 11 11
From EFrom E 11 11 00 11 11
From FFrom F 11 11 00 11 11
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Byzantine Agreement Byzantine Agreement Correctness Correctness
OverviewOverview Consider proofs received at a peer PConsider proofs received at a peer P
Set of Peers of P
t malicious peersΦn on compromised
path to A
Φn on compromisedpath to P
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Byzantine Agreement Byzantine Agreement Correctness Correctness
OverviewOverview t + 2Øn may not arrivet + 2Øn may not arrive
P receives at least n-t-2Øn proofsP receives at least n-t-2Øn proofs t + 2Øn may be faultyt + 2Øn may be faulty
P receives at least n-2t-4Øn correct agreeing P receives at least n-2t-4Øn correct agreeing proofsproofs
P decides correctly by majority if n-2t-4Øn > t P decides correctly by majority if n-2t-4Øn > t + 2Øn+ 2Øn
Agreement is correct if t < Agreement is correct if t < 1-6Ø1-6Ø//3 3 nn
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Trust GroupsTrust Groups Execute Authentication on smaller Trust groupsExecute Authentication on smaller Trust groups
Quadratic messaging costQuadratic messaging cost Peer interestPeer interest
Trusted group Trusted group Authenticated public keysAuthenticated public keys Not (overtly) maliciousNot (overtly) malicious
Probationary group Probationary group Un-trusted groupUn-trusted group
Known to be maliciousKnown to be malicious
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Growth of Trust GroupsGrowth of Trust Groups Governed by Governed by
communication communication patternspatterns
Discovery of new peersDiscovery of new peers Authentication of Authentication of
discovered peersdiscovered peers Addition to trusted setAddition to trusted set
Discovery of un-trusted Discovery of un-trusted peerspeers
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Evolution of Trust GroupsEvolution of Trust Groups Covertly malicious peersCovertly malicious peers
May wait until honest majority is violatedMay wait until honest majority is violated Lead to incorrect authentication Lead to incorrect authentication
Periodic pruning of trusted groupPeriodic pruning of trusted group Unresponsive peersUnresponsive peers Remove older trusted peers from trust groupRemove older trusted peers from trust group
Reduce messaging costReduce messaging cost Randomize trusted group membershipRandomize trusted group membership
Group migration eventGroup migration event Probability of violating honest majorityProbability of violating honest majority
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Bootstrapping Trust GroupBootstrapping Trust Group Authentication needs an honest trust Authentication needs an honest trust
groupgroup Initialize a Bootstrapping trust groupInitialize a Bootstrapping trust group Needed for cold startNeeded for cold start Authenticate each bootstrapping peerAuthenticate each bootstrapping peer
Size of bootstrapping trust groupSize of bootstrapping trust group Recover from trusting a malicious peerRecover from trusting a malicious peer
n > n > 33//1-6Ø1-6Ø
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Public Key InfectionPublic Key Infection Optimistic trustOptimistic trust
Lazy authenticationLazy authentication Reduced messaging costReduced messaging cost
Cache of undelivered messagesCache of undelivered messages Use peers for epidemic propagation of messagesUse peers for epidemic propagation of messages Anti-entropy sessions eventually deliver messagesAnti-entropy sessions eventually deliver messages Infect peers with new undelivered messagesInfect peers with new undelivered messages
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Public Key Infection Public Key Infection Use logical and vector timestamps Use logical and vector timestamps
Determine messages to exchange for anti-Determine messages to exchange for anti-entropyentropy
Detect message deliveryDetect message delivery Double exponential drop in number of Double exponential drop in number of
uninfected peers with timeuninfected peers with time Number of cached messages is in O(nlogn)Number of cached messages is in O(nlogn)
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SimulationSimulation Implemented Byzantine Fault Tolerant Implemented Byzantine Fault Tolerant
Authentication as a C++ libraryAuthentication as a C++ library Simulation programSimulation program
Make library calls and keeps countersMake library calls and keeps counters Study effects of Study effects of
Group sizeGroup size Malicious peersMalicious peers
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Effects of Group SizeEffects of Group Size Constant Cost for Constant Cost for
trusted peerstrusted peers Probationary peers Probationary peers
process O(nprocess O(n22) ) messagesmessages
Trust graph does Trust graph does not affect the costnot affect the cost Randomized Randomized
trusted sets from trusted sets from Bi-directional trustBi-directional trust
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Effects of Malicious PeersEffects of Malicious Peers Rapid increase of Rapid increase of
messaging costmessaging cost With group sizeWith group size With proportion of With proportion of
malicious peersmalicious peers Byzantine agreement Byzantine agreement
has quadratic has quadratic messaging costmessaging cost
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ConclusionConclusion Autonomous authentication without trusted third partyAutonomous authentication without trusted third party
Incremental approach to securityIncremental approach to security Suited for low value peer-to-peer systemsSuited for low value peer-to-peer systems
Tolerate malicious peersTolerate malicious peers Suited for applications spanning multiple administrative Suited for applications spanning multiple administrative
domainsdomains
Scalable to large peer-to-peer systemsScalable to large peer-to-peer systems Eliminate total trust and single point of failureEliminate total trust and single point of failure Made feasible by using stronger network assumptionsMade feasible by using stronger network assumptions
Network adversary is not all powerfulNetwork adversary is not all powerful
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OutlineOutline IntroductionIntroduction
Public key authenticationPublic key authentication Existing modelsExisting models
Motivation for Peer-to-peer authenticationMotivation for Peer-to-peer authentication Other solutions Other solutions
Byzantine fault tolerant authentication Byzantine fault tolerant authentication Security modelSecurity model Outline of correctness and performanceOutline of correctness and performance
Future workFuture work
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Future Work Future Work Applications Applications
Provide key authentication capability to Open-Provide key authentication capability to Open-SSHSSH
SSH daemons can authenticate their peersSSH daemons can authenticate their peers Provide a concise authentication summary to the Provide a concise authentication summary to the
useruser Why the public key of the server is believed/not Why the public key of the server is believed/not
believed to be what is statedbelieved to be what is stated
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Future WorkFuture Work Applications contd. …Applications contd. …
Spam identification through public key Spam identification through public key authenticationauthentication
Existing solutionsExisting solutions Filtering: Machine learning to classify contentsFiltering: Machine learning to classify contents
Results in misspellings in spam messagesResults in misspellings in spam messages False positive rate independent of sender importanceFalse positive rate independent of sender importance
Postage: Sender pays to send emailPostage: Sender pays to send email End-to-end argumentEnd-to-end argument
Safe sender listsSafe sender lists Need to authenticate senderNeed to authenticate sender
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Future WorkFuture Work Sender AuthenticationSender Authentication
Piggyback authentication protocol on email messagesPiggyback authentication protocol on email messages Messages are signedMessages are signed
They can be delivered to peers indirectlyThey can be delivered to peers indirectly SMTP allows extension fieldsSMTP allows extension fields
Authenticate senders with existing infrastructureAuthenticate senders with existing infrastructure Incremental deploymentIncremental deployment
Use digital signature to verify messages from Use digital signature to verify messages from authenticated sendersauthenticated senders
Allow messages from safe senders pass throughAllow messages from safe senders pass through Eliminate false positives from spam filtersEliminate false positives from spam filters
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Future Work Future Work Enhancements to the mechanismEnhancements to the mechanism
Address denial of serviceAddress denial of service Keep track of work done on behalf of any peerKeep track of work done on behalf of any peer Peers are authenticatedPeers are authenticated
Agreement on work done on behalf of peersAgreement on work done on behalf of peers Use authenticated load information to prevent denial of Use authenticated load information to prevent denial of
serviceservice Need economic modelNeed economic model
Avoid expensive public key cryptographyAvoid expensive public key cryptography
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Future Work Future Work Enhancements to the modelEnhancements to the model
Authenticate public keys in Ad-hoc network Authenticate public keys in Ad-hoc network Lack the network IDs assumedLack the network IDs assumed
Apply to vehicular computingApply to vehicular computing Does the public key belong to the car on GWB?Does the public key belong to the car on GWB? Working on Geographical AuthenticationWorking on Geographical Authentication
Study hybrid trust modelsStudy hybrid trust models Hierarchical, peer-to-peer, web of trust Hierarchical, peer-to-peer, web of trust
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Q&AQ&A
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Authentication ProtocolAuthentication Protocol
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ObjectiveObjective Security is an increasing concernSecurity is an increasing concern
Privacy Privacy AuthenticityAuthenticity Fault toleranceFault tolerance
Secure communication across the internetSecure communication across the internet
Distributed computation with semi-trusted Distributed computation with semi-trusted principals : Smart messagesprincipals : Smart messages
Cost effective securityCost effective security
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PrivacyPrivacy EncryptionEncryption
Computational costComputational cost Energy requirementsEnergy requirements
Our approach: nearly complete privacyOur approach: nearly complete privacy Weakened keys, shortened key lifetimeWeakened keys, shortened key lifetime Tradeoff key lifetime for computational cost at constant securityTradeoff key lifetime for computational cost at constant security
Cost effective encryption on commodity hardwareCost effective encryption on commodity hardware
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TrustTrust Trusted third party modelTrusted third party model
Used in Used in mostmost security implementations security implementations Single-point of security failureSingle-point of security failure
Our model : distributed trustOur model : distributed trust Authentication of public key is done by a vote of peersAuthentication of public key is done by a vote of peers Addition of new participantsAddition of new participants Assumption: majority can not be corruptedAssumption: majority can not be corrupted
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PerformancePerformance Lazy authentication protocol for updating the Lazy authentication protocol for updating the
public keys to peerspublic keys to peers Uses distributed trust to authenticate the new keys Uses distributed trust to authenticate the new keys Allows admission of new peersAllows admission of new peers
Dynamical encryption in Linux kernelDynamical encryption in Linux kernel Interrupt free processingInterrupt free processing Choose key lifetime based on system limitationsChoose key lifetime based on system limitations
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Status and PlanStatus and Plan Implemented encryption server on LinuxImplemented encryption server on Linux
Preliminary point to point performance evaluationPreliminary point to point performance evaluation
Investigating security of distributed trust with Investigating security of distributed trust with dynamic membershipdynamic membership
Paper in preparationPaper in preparation
Targeting active networks and mobile agentsTargeting active networks and mobile agents