MET CS690 Assignment 2: Evaluating Data Integrity and Key Length

This assignment addresses two key questions related to network security. First, it explains why simply appending a hash digest to a message does not guarantee data integrity, highlighting vulnerabilities to data alteration and the benefits of encryption. The solution emphasizes the use of public key cryptography for signature verification. Second, it discusses the impact of increasing computer speed on cryptographic algorithms, benefiting legitimate users by allowing for longer, more secure keys, while exponentially increasing the difficulty for attackers attempting brute-force attacks. The analysis demonstrates how even small increases in key length significantly hinder unauthorized key decryption efforts.

Network Security

Question 1
It has been observed that the hash digest is not enough to administer data integrity. According to
IBM Knowledge Center, the data is easily seen and understandable by the hackers if it is not
properly encrypted. This allows them to alter the data and place new data in place of the old one.
It is difficult for us to understand that the data is altered because at the time of recalculation the
old values and the new values matches. If the data will be encrypted, the hackers will not
understand it easily and will not change it and hence the data will be protected (IBM, 2013).
With the help of message digest one can easily prevent the data from getting changed by anyone
who is present in the network. It also helps in detecting whether any sort of changes are made to
the data or not, if there are any changes then the data is not passed more to the application.
Message digest is also known as one-way hash. Message digests works as a fingerprint of the
data. But if the data is altered it is difficult to figure out which corresponding digest is associated
with which altered data. Hence, the content of the hashed data is not determined from the hash.
In place of hash digest, its better to use public key cryptography as it lets the receiver to verify all
the signatures using public key and they cannot be created without the primary key (Perlman,
2016).
Question 2
The main advantage of the good guys is that there is an increase in the computer speed which
helps them. It can be said easily by the growing performance of the good guys which is
continuously growing with respect to the length of the key, and the computer speed is also
doubled then it will let the good guys to make the length of the key double without any sort of
performance penalty. This will eventually and directly impact the bad guys as the amount of keys
which needs to be evaluated will grow exponentially with respect to the length of the key making
things difficult for them (Delfs, 2015).
There will be a bad impact on the bad guys for example, if the key in the starting is 8 bits then
the bad guys will have to check only 256 keys. If there is an increase in the computer speed i.e. if
the computers runs two times faster than their original speed, within the given amount of the
processing time, hence the good guys can easily use a 16bit key but the bad guys have to check
512 keys (Mogollon, 2008). As the number of keys keeps growing exponentially and hence at

the end their will be 65,536 keys. To check this huge amount of keys the bad guys will
eventually take 128 times longer than the earliest 8-bit key.
= 65,536/512
=128
References
Delfs, H., & Knebl, H. (2015). Introduction to Cryptography. Berlin, Heidelberg: Springer.
IBM. (2013). Retrieved from
https://www.ibm.com/support/knowledgecenter/en/SSB23S_1.1.0.12/gtps7/s7dint.html
Mogollon, M. (2008). Cryptography and security services. Hershey, Pa.: IGI Global.
Perlman, R. (2016). Network Security. USA: Pearson.