privacy preserving query processing in cloud computing
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Privacy Preserving Query Processing in Cloud Computing. Wen Jie 2011-5-27. Outline. Background Privacy Preserving Query Processing Method Based on Privacy Homomorphism Processing Private Queries over Untrusted Data Cloud through Privacy Homomorphism (ICDE 2011) - PowerPoint PPT PresentationTRANSCRIPT
Privacy Preserving Query Processing in Cloud Computing
Wen Jie 2011-5-27
Outline Background Privacy Preserving Query Processing
◦ Method Based on Privacy Homomorphism Processing Private Queries over Untrusted Data
Cloud through Privacy Homomorphism (ICDE 2011)
◦ Method Based on Secret Share: Privacy Preserving Query Processing on Secret
Share Based Data Storage (DASFAA 2011)
ComparisonConclusion
BackgroundDevelopment of cloud computing
applications◦Amazon: EC2 S3◦Google: appEngine
Development of DaaS in cloud computing
Expensive hardware, software and expertise
Background
Secret Share
Method
Encryption Method
Comparison
Conclusion
Background
Security◦ Query privacy
Disclose to Cloud Disclose to DO
◦ Data privacy Disclose to Cloud Disclose to User
Background
Secret Share
Method
Encryption Method
Comparison
Conclusion
Data privacy Query privacy
Background Generalization Principal
◦Relational data: quasi-identifier◦Spatial data: location cloaking
Encrypt or transform◦Hashing◦Space filling curves
Distributed environment ◦Based on Secure Multiparty Computation
Background
Secret Share
Method
Encryption Method
Comparison
Conclusion
Processing Private Queries over Untrusted Data Cloud
through Privacy Homomorphism (ICDE 2011)
Background
Secret Share
Method
Encryption Method
Comparison
Conclusion
PreliminaryPrivacy Homomorphism
◦Encryption transformations which map a set of operations on cleartext to another set of operations on ciphertext
◦Modified ASM-PH Encryption Scheme E(e1) + E(e2) = E(e1 + e2)
E(e1) - E(e2) = E(e1 - e2)
E(e1) * E(e2) = E(e1 * e2)
Background
Secret Share
Method
Encryption Method
Comparison
Conclusion
Processing Private Queries over Untrusted Data Cloud through Privacy Homomorphism (ICDE 2011)
Architecture Key idea: let the client lead the
distance access and keep track of traversal path
Background
Secret Share
Method
Encryption Method
Comparison
Conclusion
Dist(E(e1), E(e2)) = E(dist(e1, e2))
Step 0: initialization
Architecture Key idea: let the client lead the
distance access and keep track of traversal path
Background
Secret Share
Method
Encryption Method
Comparison
Conclusion
Step 1: local distance computation
E(q) in the query
Dist(E(q), E(e1)) = E(dist(q, e1)) Scrambling Dist(E(p), E(e1))
Architecture Key idea: let the client lead the
distance access and keep track of traversal path
Background
Secret Share
Method
Encryption Method
Comparison
Conclusion
Step 2: distance decryption and recoding
Scrambled E(dist( p, e1))Decrypt to distanceRecoding the distance
Architecture Key idea: let the client lead the
distance access and keep track of traversal path
Background
Secret Share
Method
Encryption Method
Comparison
Conclusion
Step 3: find next node to traverse
Recoded distance
Local Distance Computation of Minimum Square Distance
Distance between query point q and an index entry [l, u]
Background
Secret Share
Method
Encryption Method
Comparison
Conclusion
Scrambling Notice:
◦Real distances◦Monotonic: distance compare
Two scrambling functions◦Sign computation
E(s)*E(ξ) = E (s*ξ) Receive sign(s*ξ)
◦Recoding E(s1)*E(ξ) + E(s2) = E(s1*ξ+s2)
Receive recoded(s1*ξ+s2)
Background
Secret Share
Method
Encryption Method
Comparison
Conclusion
Depend on sign(s)
Depend on sign(s1)
Distance Decryption and RecodingDecryption with E-1 (· )
Recoding properties◦Strictly monotonic
Key idea: record all existing recoded value pairs (real valued, recoded value) at cloud side
◦Immune to chosen ciphertext attack Key idea: recoded values are random
Background
Secret Share
Method
Encryption Method
Comparison
Conclusion
Processing Distance Range QueriesQuery: find all records whose
distances are within r from point q
Background
Secret Share
Method
Encryption Method
Comparison
Conclusion
s1*4r2 + s2
Recoding
Recoded 4r2
Processing Distance Range QueriesQuery: find all records whose
distances are within r from point q
Background
Secret Share
Method
Encryption Method
Comparison
Conclusion
Recoded 4r2
E(s1)*dist(E(e1), E(q)) + E(s2)
DecryptionRecoding
Processing Distance Range QueriesQuery: find all records whose
distances are within r from point q
Background
Secret Share
Method
Encryption Method
Comparison
Conclusion
Recoded 4r2
Recoded dist(e1, q)
Performance Analysis
Distance Range Query Performance
Background
Secret Share
Method
Encryption Method
Comparison
Conclusion
distance threshold
Privacy Preserving Query Processing
on Secret Share Based Data Storage
(DASFAA 2011)
Secret Share
Method
Encryption Method
Comparison
Conclusion
Background
Preliminary Secret share scheme
◦protect sensitive information by dividing the value into n shares
The scheme is called (k, n) threshold scheme if it satisfies: ◦k or more shares reconstruct the
value◦k-1 or less shares make the value
completely undetermined
Secret Share
Method
Encryption Method
Comparison
Conclusion
Background
Privacy Preserving Query Processing on Secret Share Based Data Storage (DASFAA 2011)
Architecture
Three parties◦ Data Owner (DO)◦ Database Service
Provider (DSP)◦ Data Requestor (DR)
How it works◦ Delegate data (DO) ◦ Build an index (DO)◦ Process a query (DR)
Secret Share
Method
Encryption Method
Comparison
Conclusion
Background
Privacy preserving index
Secret Share SchemeA share is the result value y
Given known x1 x2 … xn , n shares are y1 y2 … yn .
Any k pairs of (x1, y1), (x2, y2)… (xk, yk) can reconstruct the above polynomial
Secret Share
Method
Encryption Method
Comparison
Conclusion
Background
Real value
Data DivisionData Division at DO with (3, 5)
threshold scheme◦Randomly choose a polynomial
on finite domain F103
◦Choose a minimum generator = 5
X = {5, 25, 22, 7, 35}
◦Share(20, 1) = 82; Share(20, 2) = 79; Share(20, 3) = 14;
Share(20, 4) = 87; Share(20, 5) = 102
Secret Share
Method
Encryption Method
Comparison
Conclusion
Background
Data Divisionempno name salary
20060019 Mary 82
20060011 John …20050012 Kate …
20050001 Mike …
20040018 Henry …Secret Share
Method
Encryption Method
Comparison
Conclusion
Background
empno name salary
20060019 Mary 79
20060011 John …20050012 Kate …
20050001 Mike …
20040018 Henry …
empno name salary
20060019 Mary 14
20060011 John …20050012 Kate …
20050001 Mike …
20040018 Henry …
DSP1
DSP2 DSP3 DSP4
DSP5
empno name salary
20060019 Mary 87
20060011 John …20050012 Kate …
20050001 Mike …
20040018 Henry …
empno name salary
20060019 Mary 102
20060011 John …20050012 Kate …
20050001 Mike …
20040018 Henry …
Data Reconstruction
Secret Share
Method
Encryption Method
Comparison
Conclusion
Background
Private Data Reconstruction at DR◦DR needs at least k shares of the value◦Lagrange interpolation to reconstruct
the polynomial
Storage Model
Secret Share
Method
Encryption Method
Comparison
Conclusion
Background
All relations like R(A1, A2, … ,Am) are stored into n DSPs in the form of following relation:
Source attribute
key attribute
Key Generation Function
Secret Share
Method
Encryption Method
Comparison
Conclusion
Background
Key value = bucket_id || encrypted_sal
◦Bucket_id makes sure that values are in order
◦Use a symmetric algorithm DES and the random key to encrypt salary value
Index Creation Function
Secret Share
Method
Encryption Method
Comparison
Conclusion
Background
B+ index
Query Processing
Secret Share
Method
Encryption Method
Comparison
Conclusion
Background
Employee name and salary are both divided into n shares
SELECT name FROM Employees WHERE salary = 35
Encrypt 35 using DES scheme into h8jbka8g
Search in metedata for key_sal: 128h8jbka8g
search index on attribute key_sal
K sub queries
reconstruct name from k shares
Experiments EvaluationSecurity analysis
◦DSPs collude with each other◦DR colludes with at least k DSPs
Secret Share
Method
Encryption Method
Comparison
Conclusion
Background
Experiments EvaluationEfficiency Evaluation
◦Time comparison between hash based searching and index based searching
Secret Share
Method
Encryption Method
Comparison
Conclusion
Background
Experiments EvaluationEfficiency Evaluation
◦Time comparison between encryption and polynomial computation
◦Data extension and tuplesize
Secret Share
Method
Encryption Method
Comparison
Conclusion
Background
Comparison
Secret Share
Method
Encryption Method
Comparison
Conclusion
Background
Encryption Method Secret Share Method
Data location Data owner Cloud
Index location Client (shadow index) Cloud
DO involvement Initialization: Send shadow index to clientSend key to cloud
Outsourcing:Data divisionIndex creation
Client Computation
Node traversal Local distance computationDistance comparison
Query transformationResults reconstruction
Cloud Computation
Encryption DecryptionRecoding
Query processing
Communication Costs
High Low
Conclusion PH Encryption Method
◦Low efficiency ◦Data privacy preservation ◦Query privacy preservation
Secret Share Method◦High efficiency◦Data privacy preservation ◦Query privacy leak when DO colludes
with cloud
Secret Share
Method
Encryption Method
Comparison
Conclusion
Background
Q&A?Thank you~