Encryption-Based Multilevel Model for DBMS - Multilevel Security for Relational Databases - page 106

models and the encryption-based multilevel database model when
executing the JOIN query. The overhead of the decryption is included
in the evaluation of the performance of the multilevel data retrieval.
The where clause in the JOIN query will be taken into consideration
when we evaluate the performance of the multilevel database security
models and the encryption-based multilevel database model when
executing the JOIN query. The JOIN operation involves two tables:
the employee table and the departure table. The JOIN statement that
is used in the following experiments is described as follows:

Select * from Employee join Departure
on Employee.Name = Departure.Name where Employee.
department = 'Sales'

5.4.3.1 Impact of Varying the Number of Tuples he number of tuples
is varied from 100,000 to 500,000, 1,000,000, 1,500,000, and
2,000,000. Fix the number of attributes at three; fix the number of
security levels at four. From Figure 5.11 the response times grow

50

Number of attributes = 3
Number of security levels = 4

45

40

35

30

25

20

15

10

5

0

0 0.5 1

Number of Tu ples

1.5 2

Millions

SeaView
MLR

Jajodia-Sandhu
Belief-Consistent

Smith-Winslett
MLS-Encryption

Figure 5.11 Impact of changing the number of tuples in a join query. (V. M. Doshi et al. 1996.
Proceedings of IEEE Transactions on Knowledge and Data Engineering 8 (1): 46-55.)