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Question# 1 : [ 1 Mark ] Suppose that we have a computer that can test 2 4 0 or ( 2 ^ 4 0
Question#: Mark
Suppose that we have a computer that can test or Question# : Mark
Suppose that we have a computer that can test keys each second.
a What is the expected time in years to find a key by exhaustive search
if the key size is bits?
b What is the expected time in years to find a key by exhaustive search
if the key size is bits?
Question# : Marks
Decrypt the ciphertext
"TDEUNOTFTHAKITNFGAHDEOMCPTUEREIMAAPORUDSNINGEREINGUIVNES
RITYDPAERMTENT"
This message was encrypted with a double transposition of the type discussed
in the text using a matrix of rows and columns. Hint: The first words
are "I am
Question#: Marks
Suppose that Alice's RSA public key is
a Find her private key,
b If Bob encrypts the message using Alice's public key, what is the
ciphertext C Show that Alice can decrypt C to obtain M
c Let be the result when Alice digitally signs the message What
is If Bob receives and explain the process Bob will use to verify
the signature and show that in this particular case, the signature
verification succeeds.
Question#: Mark
On a particular system, all passwords are characters, there are choices
for each character, and there is a password file containing the hashes of
passwords. Trudy has a dictionary of passwords, and the probability that
a randomly selected password is in her dictionary is Work is measured in
terms of the number of hashes computed.
a Suppose that Trudy wants to recover Alice's password. Using her
dictionary, what is the expected work for Trudy to c keys each second.
a What is the expected time in years to find a key by exhaustive search if the key size is bits?
b What is the expected time in years to find a key by exhaustive search if the key size is bits?
Question#: Marks
Decrypt the ciphertext
TDEUNOTFTHAKITNFGAHDEOMCPTUEREIMAAPORUDSNINGEREINGUIVNESRITYDPAERMTENT
This message was encrypted with a double transposition of the type discussed in the text using a matrix of rows and columns. Hint: The first words are I am
Question#: Marks
Suppose that Alices RSA public key is N e
a Find her private key, d
b If Bob encrypts the message M using Alices public key, what is the ciphertext C Show that Alice can decrypt C to obtain M
c Let S be the result when Alice digitally signs the message M What is S If Bob receives M and S explain the process Bob will use to verify the signature and show that in this particular case, the signature verification succeeds.
Question#: Mark
On a particular system, all passwords are characters, there are choices for each character, and there is a password file containing the hashes of passwords. Trudy has a dictionary of passwords, and the probability that a randomly selected password is in her dictionary is Work is measured in terms of the number of hashes computed.
a Suppose that Trudy wants to recover Alices password. Using her dictionary, what is the expected work for Trudy to crack Alices password, assuming the passwords are not salted?
b Repeat part a assuming the passwords are salted.
c What is the probability that at least one of the passwords in the password file appears in Trudys dictionary?
Question#: Marks
Suppose all passwords on a given system are characters and that each character can be any one of different values. The passwords are hashed with a salt and stored in a password file. Now suppose Trudy has a password cracking program that can test passwords per second. Trudy also has a dictionary of common passwords and the probability that any given password is in her dictionary is The password file on this system contains password hashes.
a How many different passwords are possible?
b How long, on average, will it take Trudy to crack the administrators password?
c What is the probability that at least one of the passwords in the password file is in the dictionary?
d What is the expected work for Trudy to recover any one of the passwords in the password file?
Question#: Marks
Suppose that when a fingerprint is compared with one other nonmatching fingerprint, the chance of a false match is in which is approximately the error rate when points are required to determine a match as in the British legal standard. Suppose that the FBI fingerprint database contains fingerprints.
a How many false matches will occur when suspect fingerprints are each compared with the entire database?
b For any individual suspect, what is the chance of a false match?
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