CSE 539 - Applied Cryptography
Problem Set 2
Fall 2016
Note that the provided solutions are not meant to be complete detailed solutions. They are meant
to help you determine if your answer is correct
1
PRG
Problem 1. Let G be a PRG with expansion factor `
CS 435: Introduction to Cryptography
2012 Fall
Solutions 2
Professor Somesh Jha
1. Let m M, and consider any distribution over M that assigns a probability of 0
to m. Then, for any c C for which Pr[C = c] > 0, we have that
Pr[M = m C = c]
Pr[C = c]
Pr[M =
CSE 539 - Applied Cryptography
Problem Set 4
Fall 2016
1
PRFs
Problem 1. Let F be a length preserving pseudorandom function. For the following construction of
keyed function, state whether F 0 is a pseudorandom function.
def
1. Fk0 (x) = Fk (x) x
def
2. F
Jonathan Katz and Yehuda Lindell
Introduction to Modern
Cryptography
c
2007
Jonathan Katz and Yehuda Lindell. All Rights Reserved
CRC PRESS
Boca Raton London
New York
Washington, D.C.
Preface
This book presents the basic paradigms and principles of modern
Perfect Secrecy and
one-time pad
CSE 539 Fall 2016
Rida Bazzi
Encryption
M
C
:
:
K
Gen
:
:
Enc
:
Dec
:
message space which is the set of messages
cipher text space is the set of cipher texts that can be
produced
key space which is the set of possible keys
CS 202: Introduction to Applied Cryptography
Feb 9, 2012
Homework 2: Solutions
Exercise 2.2: This was not true in general, i.e. its not true for every distribution over
the message space. If the scheme is perfectly secure then P r[M = m|C = c] = P r[M = m
CSE 539 - Applied Cryptography
Problem Set 3
Fall 2016
Note that all the provided solutions are complete detailed solutions. They are meant to help you
determine if your answer is correct
1
PRFs
Problem 1. Let F be a length preserving pseudorandom functio
CSE 539 Fall 2016
Quiz 1
9 2 2016
In order to get credit on any of the question, you should answer all parts of the question
correctly. Guessing will not help!
1. Consider the following scheme on message space cfw_0,1n+1
Gen: k cfw_0,1n
Enck(m) = 0|k m
A
CSE 539 - Applied Cryptography
Fall 2016
1
Personnel
Instructor: Rida A. Bazzi
E-mail:
Phone:
Office:
2
[email protected]
480 965-2796
BY 430
Office Hours
Office hours are TBD in class
I encourage you to come to my office hours to ask any questions you have
a
Computational Security
CSE 539 Fall 2016
Rida Bazzi
So far
Perfect secrecy. Three equivalent formulations
For any distribution on the message space
1. Pr[M = m | C = c] = Pr[M = m]
1. Pr[C = c | M = m0] = Pr[C = c | M = m1]
For any adversary
3. Pr[Succes
Perfect Secrecy,
Probability Review, and
Classical Ciphers
CSE 539 Fall 2016
Rida Bazzi
Setup
k : key shared between the two parties
adversary
E : encryption function. Ek(m) is the cipher text obtained by
encrypting m using key k
D : decryption function.
One-time pad,
Perfect Secrecy and Perfect
Indistinguishability
CSE 539 Fall 2016
Rida Bazzi
One-time pad: what does perfect secrecy mean?
Assume M = cfw_000, 111 subset of cfw_0,1
n
the one-time pad k is selected uniformly at random: k <- cfw_0,1
To keep
CSE 539 - Applied Cryptography
Problem Set 1
Fall 2016
Note that these solutions are not meant to be complete detailed solutions. They are meant to help
you determine if your answer is correct
1
Classical Schemes
Problem 1. Define Gen, Enc, and Dec, for a