Cryptography Reference
In-Depth Information
FIGURE 16.1
(c)
(d)
16.2
DATABASE ENCRYPTION
The Chinese Remainder Theorem can also play a role in enciphering databases. It can be
done so that a particular user only has access to their data. A database is a collection of
records
R
1
,
R
2
, ...,
R
n
. We can regard each record as an integer, for they are basically stored
this way.
We first choose a sequence
p
1
,
p
2
, ...,
p
n
of distinct primes with
p
i
>
R
i
for
i
= 1, 2, . . . ,
n
. As the enciphered database we will use an integer
C
that is congruent to
R
i
modulo
p
i
∀
i
. Such an integer exists and is computable by the CRT. Let
M
=
p
1
p
2
...
p
n
and let
M
i
=
M
/
p
i
for each
i
. Now, let
w
i
=
M
i
M
i
where
M
i
is an inverse of
M
i
modulo
p
i
.
We compute the enciphered database as
C
w
i
R
i
(mod
M
)
0
≤ C
<
M
,
i
= 1, 2, ...,
n
.
w
n
the write subkeys of the database cipher, for these will be required
to write to the database; that is, they are required to construct
We call
w
1
,
w
2
, ...,
C
. The moduli, however,
p
1
,
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