1
.
Block
____________________
are
among
the
most
widely
used
types
of
cryptographic
algorithms
provide
secrecy
and
/
or
authentication
services
.
2
.
In
1949
Claude
Shannon
introduced
idea
of
substitution
-
permutation
(
S
-
P
)
networks
.
S
-
P
networks
are
based
on
the
two
primitive
____________________
operations
we
have
seen
before
:
substitution
(
S
-
box
)
and
permutation
(
P
-
box
)
while
they
provide
confusion
and
diffusion
of
message
.
3
.
diffusion
?
dissipates
____________________
structure
of
plaintext
over
bulk
of
ciphertext
confusion
?
makes
relationship
between
ciphertext
and
key
as
____________________
as
possible
4
.
Data
Encryption
Standard
(
DES
)
has
been
considerable
controversy
over
its
____________________
.
DES
has
become
widely
used
,
especially
in
financial
applications
5
.
Initial
Permutation
IP
:
first
step
of
the
data
computation
IP
reorders
the
input
data
____________________
even
bits
to
LH
half
,
odd
bits
to
RH
half
quite
regular
in
structure
(
easy
in
h
/
w
)
example
:
IP
(
675a6967
5e5a6b5a
)
=
(
ffb2194d
004df6fb
)
6
.
____________________
Effect
:
key
desirable
property
of
an
encryption
algorithm
where
a
change
of
one
input
or
key
bit
results
in
changing
approx
half
output
bits
making
attempts
to
?
home
-
in
?
by
guessing
keys
impossible
7
.
3DES
uses
3
keys
and
3
DES
executions
:
(
a
)
using
3
keys
3DES
has
an
effective
key
length
of
168
bits
(
3
*
56
)
(
b
)
follows
encrypt
-
____________________
-
encrypt
(
EDE
)
(
c
)
the
decryption
phase
is
for
backwards
compatibility
with
single
DE
S
