CSE 794Q Homework 2
Due: Wednesday, April 21 by class time
1.
Consider an encryption scheme (
G, E, D
).
Show that if the encryption algorithm
E
is
deterministic (rather than probabilistic), then the encryption scheme cannot be multiple
ciphertext indistinguishable.
2.
Let G be a pseudorandom generator with expansion factor
( )
2 .
l n
n
Define
2
( )
( )
for
{0,1} and
{0,1} .
nn
k
f x
G k
x
k
x
Is
:
{0,1}
n
k
fk
a family of
pseudorandom functions?
Justify your answer.
3.
Let G be a pseudorandom generator with expansion factor
( )
1.
l n
n
Construct an
encryption scheme as follows.
To encrypt a message
22
0,1
,
n
m
parse
m
as
12
mm
with

 
,
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 Spring '10
 TenH.Lai
 Cryptography, Encryption, Encryption algorithm, encryption scheme

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