Databases Reference
In-Depth Information
Client Site
Server Site
Result
Filter
Temporary
Results
Encrypted Results
Query over Encrypted Data
Query
Translator
Service Provider
Meta
Data
Original Query
Encrypted
Client
Database
Web Browser
(USER)
Fig. 1.
Query Processing in DAS
query over un-encrypted relations are broken into (1) a server-query over
encrypted relations which run on the server, and (2) a client-query which
runs on the client and post-processes the results returned after executing the
server-query. We achieve this goal by developing an algebraic framework for
query rewriting over encrypted representation.
2.3 Relational Encryption and Storage Model
For each relation
R
(
A
1
,A
2
,...,A
n
)
one stores on the server an encrypted relation:
R
S
(
etuple, A
1
,A
2
,...,A
n
)
where the attribute
etuple
stores an encrypted string that corresponds to a
tuple in relation
R
. Each attribute
A
i
corresponds to the index for the at-
tribute
A
i
and is used for query processing at the server. For example, consider
a relation
emp
below that stores information about employees.
eid ename salary addr
did
23
Tom
70K
Maple
40
860 Mary 60K
Main
80
320 John
50K
River
50
875 Jerry
55K
Hopewell 110
The
emp
table is mapped to a corresponding table at the server:
emp
S
(
etuple, eid
S
, ename
S
, salary
S
, addr
S
,did
S
)
