STRUDEL: STRUDEL: Supporting Trust Supporting Trust

in the Dynamic Establishmentin the Dynamic Establishmentof peering coaLitionsof peering coaLitions

April 2006

Daniele Quercia, Manish Lad,

Stephen Hailes, Licia Capra,

and Saleem Bhatti

CS departmentUniversity College London{d.quercia}@cs.ucl.ac.uk

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Daniele Quercia

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STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions

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Outline

Novel and existing mechanisms to support those features

To avoid tragedy, STRUDEL supports 4 features

Mesh Net and its tragedy

How STRUDEL supports them? State machine

One experiment & Conclusion

Daniele Quercia

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Mesh net and its tragedy

Mesh nodes form a peering coalition

Result:

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STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions

Free-riders join the coalition

Result:

Bandwidth sharing

Tragedy (of the commons)

Daniele Quercia

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To avoid tragedy, STRUDEL supports 4 Features

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STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions

STRUDEL needs distributed mechanisms to:

form peering coalitions;

detect free-riders;

manage (trust) info;

decide such that free-riders excluded.

Daniele Quercia

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Novel and existing work to support...

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STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions

form detect

manage decide

Daniele Quercia

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STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions

STRUDEL needs to form peering coalitions. How? Common (Connection sharing in MANETs): Each device in turn acts as a gateway

form detect

manage decide

px

py

pz

Daniele Quercia

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STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions

Novel (Connection sharing in Mesh Nets) : Devices share multiple connections simultaneously

form detect

manage decide

px

py

pz

CPD

M. Lad, S. Bhatti, S. Hailes, and P. Kirstein. Enabling Coalition-Based Community Networking. In Proc. of the London Communications Symposium. 2005.

Daniele Quercia

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STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions

STRUDEL needs to detect free-riders. How?

2-ACK scheme:

form detect

manage decide

px py pzOne-hop ACK Two-hop ACK

Two-hop ACK

packet packet

If px does not receive:

one-hop ACK retransmits

two-hop ACK is suspicious about py

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STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions

STRUDEL needs to manage trust info. How?

form detect

manage decide

Existing distributed

trust management

Fine-grained

trust metric

2+ Trust Sources

Time Formalization

Abdul-Rahmal [2] X XConfidant [4] X

?

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STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions

form detect

manage decide

How ? Fine-grained

trust metric

2+ Trust Sources Time Formalization

B-trust n-level

Direct experiences

& Recommendations

Aging

Bayesian

Quercia; Hailes; CapraB-trust: Bayesian Trust Framework for Pervasive ComputingProceedings of the 4th International Conference on Trust Management. LNCS. 2006.

Daniele Quercia

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STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions

Upon trust info, STRUDEL (px) needs to decide whether

to exclude (cooperate). How? For each next-hop py, px has a table:

form detect

manage decide

Quercia ; Hailes Risk Aware Decision Framework for Trusted Mobile InteractionsProceedings of the 1st IEEE SECOVAL Workshop (in conjunction with SECURECOMM).

(b) py’s actions

Send now

Send

Don’t send

Send Just-in-time

Send Out-of-time

Sent Sent just-in-time

Sent out-of-time

Not sent(a)

px’

s ac

tions

(c) Expected Outcomes

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STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions

CPD 2-ACK

B-trust Utility

Support of the 4 Features

How ?

Daniele Quercia

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STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions

How? State Machine!

Wait Ready

Next Hop: px selects whether to send packets and, if so, chooses its next-hop

Update:px updates its direct trust and recommended trust in its next-hops

WAIT

RESEND

SLOWSTART

MALIC. AVOIDANCE

SEND

NEXT HOP

IDLEADVAGREEMENT

Send(ADV

,-)

{no

hop

}{a

bove

tru

st

thre

sho

ld}

{qu

it C

PD

}

{update complete}

RCV(JR, p Y)

{miss 2 ACK}

{miss 1 ACK}

{miss 1ACK}

{above benevolence threshold}

{below trust threshold}

{mar

k

unre

spon

sive}

{burst losses}

{mis

s 2

AC

K}

Rcv(RA,pY)

Send(RD,pY) {Out CPD}

Send(RD,p Y)

{In CPD}

Sen

d(R

A,p

Y)

{bandwidth change}

T

ADV

{ pkt to be sent}

UPDATE

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STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions

How? State MachineSend: px sends packets without 2-ACK scheme;

Slow Start: px sends q packets (initially, q=1).If it receives 2-hop ACK, px increases its sending window by q.

Maliciousness avoidance:px increases linearly its sending window

WAITUPDATE

RESEND

SEND

NEXT HOP

IDLEADVAGREEMENT

Send(ADV

,-)

{no

hop

}{a

bove

tru

st

thre

sho

ld}

{qu

it C

PD

}

{update complete}

RCV(JR, p Y)

{miss 2 ACK}

{miss 1 ACK}

{miss 1ACK}

{above benevolence threshold}

{below trust threshold}

{mar

k

unre

spon

sive}

{burst losses}

{mis

s 2

AC

K}

Rcv(RA,pY)

Send(RD,pY) {Out CPD}

Send(RD,p Y)

{In CPD}

Sen

d(R

A,p

Y)

{bandwidth change}

T

ADV

{ pkt to be sent}

SLOWSTART

MALIC. AVOIDANCE

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STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions

One experimentWhen using STRUDEL, px successfully sent

. 67% of the packets on average (if n=2),

. 84% (if n=4),

in contrast to 42% when using random selection.

px

fm

m

b

fb

100%

70%

30%

15%

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STRUDEL: Supporting Trust in the Dynamic Establishment of peering coaLitions

Conclusion

STRUDEL forms peering coalitionsdetects free-ridersmanages trust info, upon which itteams up only with trustworthy peers

Future work:

Fully implement STRUDEL