sonia jahid, prateek mittal, nikita borisov university of illinois at urbana-champaign presented by...
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EASiER: Encryption-based Access Control in Social Networks with Efficient Revocation
Sonia Jahid, Prateek Mittal, Nikita Borisov
University of Illinois at Urbana-Champaign
Presented by Nikita BorisovASIACCS 2011
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Motivation
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Encryption
Encrypt social network data flyByNight [Lucas&Borisov’08] NOYB [Guha et al.’09] FaceCloak [Luo et al.’09] Persona [Baden et al.’09]
Users directly control access Grant access by distributing keys Revoke access by…?
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Revocation
4
Alice
Bob Carol Diana
Existing Data
Expensive!
Our Contribution:Efficient revocation without rekeying or
re-encryption, by using a minimally trusted proxy
Re-encrypt
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System Architecture
5
Bob Carol Diana
KeyProxy (Revoke Bob)
Proxy
Modified CTcomponent
CTcomponent
PK, MK
1 AND Colleague
Neighbor
OR
Friend
friend, neighbor
colleague friend,colleague
Alice
SetupKeyGenEncryptRevoke/KeyProxyConvertDecrypt
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Algorithms - Basic Idea(cf. [Naor&Pinkas’00])
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SKr,r
1
SKr,r
2
SKr,r
3
SKr,r
4
CT CT’
SK
Convert
Point to Determine, P(0)
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Security
Immediate revocation As soon as proxy updated Including past data
Minimally trusted proxy Cannot decrypt data Cannot “unrevoke” users even if
compromised
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Evaluation
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Encrypt Decrypt Keygen0
1
2
3
4
5
6
7
8
9
CP-ABECP-ABE-MNTEASiER
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Evaluation- Proxy Rekey
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0 100 200 300 400 5000
0.20.40.60.8
11.21.4
Users Revoked
Tim
e t
o R
eke
y P
roxy
(seco
nd)
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Comparison
Conventional revocation Rekey 500 friends: 5s Decrypt 2000 items: 13s Encrypt 2000 items: 36s
EASiER: 1.5s
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Evaluation - Conversion
11
0 20 40 60 80 100
00.20.40.60.8
11.21.4
Leaf Nodes in Policy
Convers
ion T
Ime
(seco
nd)
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Conclusion
We introduced an efficient revocation scheme for ABE Useful in OSNs
Potential uses in other ABE deployments
Open problems Forward security of
proxy
Stronger security proofs
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Sonia Jahid
Prateek Mittal
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Questions?
13
Sonia Jahid
Prateek Mittal