Math 187 Prof. Garsia typed by Alex Brik 05-12-2009 Sample Quiz 6 Solution 1. YOU ARE DOING FINE 2.
A 010 B 00000 C 0001 D 001 E1 F 011 G 00001 Length = 670
1
4. H (X jY ) is bits of information learned when given the value of X , assuming that the value
Cryptography: An Introduction
(3rd Edition)
Nigel Smart
Preface To Third Edition
The third edition contains a number of new chapters, and various material has been moved
around.
The chapter on Stream Ciphers has been split into two. One chapter now deals
Problem 1:
(a) 45137826
(b) diagram:
(c) IF WE COULD FIRST KNOW WHERE WE ARE, AND WHITHER WE ARE TENDING,
WE COULD THEN BETTER JUDGE WHAT TO DO, AND HOW TO DO IT. WE ARE NOW
FAR INTO THE FIFTH YEAR, SINCE A POLICY WAS INITIATED, WITH THE AVOWED
OBJECT AND
Quiz 6 on Monday March 13
SAMPLE QUIZ 6
1. Suppose a certain file contains only these letters with the following frequencies:
Construct the comma free code that enables you to compress the file so that you
can store it using the least number of bits.
E
3
SAMPLE QUIZ 5
1. Suppose that you intercept the Vernam encrypted ciphertext
XJNRJ QPISY BZGZM AJHCL LZ
Suppose further that p = 3, q = 4, and that the original plaintext starts with KEEPCA.
(a) Reconstruct the encryption vectors A (of length p) and B (o
SAMPLE QUIZ 1
1. Decipher the message
SFSBM OLOFM WCSYB DVOSH OWVKG KFSUR HCCVI DWYB
knowing that it was encrypted using a Vigenre cipher with a 2-letter key.
Hint: The most common letter in English is E.
2. Decipher the message
IH TS IS AL PT NI TX E
kno
SAMPLE QUIZ 4
1. Suppose the random variables X, Y, Z are obtained by spinning the adjoining
roulette wheel, with X given by the outermost circle, Y given by the intermediate
circle and Z given by the inner circle.
(a) Calculate E[Z] (the expectation of
SAMPLE QUIZ 3
1. Find the inverse of 115 modulo 12659 by Berlekamp's algorithm and show ALL the
computational steps.
2. Decipher message
XI NQ X3 XI F8 X3
knowing that it is a Hill cipher with modulus 37 and key matrix
A=
5
2
12
5
using the following tabl
SAMPLE QUIZ 2
1. Decipher the message
P
J
Z
M
E
P
M
J
Z
W
E
B
Y
knowing that it was encrypted using a Vernam cipher with keys U = (3,5) and V = (16, 23, 18).
2. Compute
a = 19787467390475022 - 592750282085 (mod 43) and b = - a (mod 43).
3. A certain binar
Math 187 Prof. Garsia (typed by Alex Brik) 04-06-2009
SAMPLE QUIZ 1 solution. 1. Let 1,2,3,.,n be an indexing of ciphertext letters. A Vigenere cipher with a 2 letter key will encryot every letter with index k 1 (mod 2) using rst letter of the key, and wi