CIS3360: Security In Computing 1
Download this Homework Solution to explore fundamental cybersecurity concepts.
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CIS3360: Security in Computing
Homework 5
1. ( 15 points) Knowledge-based Question:
a. What are the differences between public/symmetric key cryptography? The advantage
and disadvantage of each?
Symmetric Cryptography involves 2 people using the same private key to encrypt and
decrypt information. While in Public key cryptography there are 2 different keys that are
used, a public key for encryption and a private key for decryption.
Public Key Cryptography
Advantages
The public key does not have to be secured that is why it is public. Which anyone can
use. It is much more secure than Symmetric Cryptography.
Disadvantages
It is harder to implement and slower than Symmetric cryptography.
Symmetric Key Cryptography
Advantages
It is much easier to implement, and takes up much less processing power.
Disadvantages
It is less secure; both parties have to agree on the same private key to use.
a. For English alphabet based texts regardless of upper or lower case (i.e., assuming each
letter has only 26 possible value), if the length of the key using Vigenere Cipher is 4, how
many possible encryption keys exist? (hint: we all know that Caesar cipher has 26
possible encryption keys)
26^4 possible encryption keys.
b. What is the usage of a cryptographic hash function? Can two documents have the same
hash value?
The primary use of cryptographic hash function is for message integrity. Yes it is possible
for 2 documents can have the same hash value.
2. (10 points) Determine whether a statement is True or False. If a statement is false, you must
explain why.
a. Digital signature of a message m is H(m), where H() represent a cryptographic hash
function such as MD5 or SHA-1.
TRUE.
Homework 5
1. ( 15 points) Knowledge-based Question:
a. What are the differences between public/symmetric key cryptography? The advantage
and disadvantage of each?
Symmetric Cryptography involves 2 people using the same private key to encrypt and
decrypt information. While in Public key cryptography there are 2 different keys that are
used, a public key for encryption and a private key for decryption.
Public Key Cryptography
Advantages
The public key does not have to be secured that is why it is public. Which anyone can
use. It is much more secure than Symmetric Cryptography.
Disadvantages
It is harder to implement and slower than Symmetric cryptography.
Symmetric Key Cryptography
Advantages
It is much easier to implement, and takes up much less processing power.
Disadvantages
It is less secure; both parties have to agree on the same private key to use.
a. For English alphabet based texts regardless of upper or lower case (i.e., assuming each
letter has only 26 possible value), if the length of the key using Vigenere Cipher is 4, how
many possible encryption keys exist? (hint: we all know that Caesar cipher has 26
possible encryption keys)
26^4 possible encryption keys.
b. What is the usage of a cryptographic hash function? Can two documents have the same
hash value?
The primary use of cryptographic hash function is for message integrity. Yes it is possible
for 2 documents can have the same hash value.
2. (10 points) Determine whether a statement is True or False. If a statement is false, you must
explain why.
a. Digital signature of a message m is H(m), where H() represent a cryptographic hash
function such as MD5 or SHA-1.
TRUE.
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Document Details
University
University of South Florida
Subject
Information Technology