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Tight Tradeoffs in Searchable Symmetric Encryption
Gilad Asharov Gil Segev Ido Shahaf
Hebrew University Hebrew University Cornell Tech
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Tight Tradeoffs in Searchable Symmetric Encryption Gilad Asharov - - PowerPoint PPT Presentation
Tight Tradeoffs in Searchable Symmetric Encryption Gilad Asharov - - PowerPoint PPT Presentation
Tight Tradeoffs in Searchable Symmetric Encryption Gilad Asharov Gil Segev Ido Shahaf Cornell Hebrew Hebrew Tech University University The Efficiency of SSE [CT14] 2 Existing Schemes and Lower Bounds Space Locality Read efficiency
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Existing Schemes and Lower Bounds
Space Locality Read efficiency [CGKO06, KPR12, CJJKRS13] [CT14] [ANSS16]-#1 [DP17] Lower bound for schemes with non-overlapping reads [CT14]
Can we close the gap between the upper bounds and lower bounds?
We consider schemes that
- do not modify the encrypted database while searching
- have “minimal leakage” =
+ +
ORAM-based techniques [DPP18] not captured
size of database size of each result query repetition pattern
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Can we close the gap between the upper bounds and lower bounds?
Existing Schemes and Lower Bounds (cont.)
Not all schemes have non-overlapping reads!
Space Locality Read efficiency [ANSS16]-#2 [ANSS16]-#3 (1) Lower bound for the statistical-independence framework [ANSS16]
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Refines the non-overlapping reads property while still capturing the same existing schemes
Pad-and-Split Framework
Our Contributions
Current SSE Techniques
Statistical-Independence Framework
Main result:
- A tight lower bound
- Matches the scheme of [DP17]
Main result:
- An improved upper bound
- Matches the [ANSS16] lower
bound for a range of parameters
NEW
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Pad-and-split framework: Statistical-independence framework:
Our Contributions (cont.)
Space Locality Read efficiency
Our scheme (1) Lower bound [ANSS16]
Space Locality Read efficiency
Our lower bound The [DP17] scheme
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This Talk: Our Scheme
See our paper for the pad-and-split framework and lower bound
Space Locality Read efficiency
Our scheme
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The [ANSS16] 2-Dim 2-Choice Allocation
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Our Approach: Allow Overflow!
What should we do with the overflowing lists? ?
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Naïve Attempt
[ANSS16]-#1 The problem: Revealing which lists are
- verflowing leaks information!
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Our Solution
- Modify the [ANSS16]-#1 scheme such that it will not reveal whether
a list is stored in it
- Key idea: Avoid rehashing using cuckoo hashing with a stash
- Stash size depends on the length of the list
Stash size Bin size
[ANSS16]-#1
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Summary Thank you!
Refines the non-overlapping reads property while still capturing the same existing schemes
Pad-and-Split Framework
Current SSE Techniques
Statistical-Independence Framework
Main result:
- A tight lower bound
Main result:
- An improved upper bound
NEW