CST 311 Week 4 Journal Entry

 Security In Computer Networks

This week, we learned about security in computer networks. There are three principles of network security: confidentiality, authentication, and message integrity. Confidentiality involves ensuring that only the sender and receiver understand the message being sent. Authentication involves confirming the identity of both the sender and receiver. Message integrity involves ensuring that the message has not been altered while being transmitted or after it has been transmitted. 

Confidentiality can be obtained by having the user and sender use the same symmetric keys to encrypt and decrypt the messages between them. A symmetric key is a key that both the sender and receiver agree upon. Currently, the Advanced Encryption Standard is used to create symmetric keys. Using this standard, we can process our data and message into 128-bit blocks and use 128, 192, or 256-bit keys to create our symmetric key. 

When deciding on a key to use, the sender and receiver can decide to use a public key. The public key is known to everyone and the sender uses the receiver's public key to encrypt the message. The receiver can then use their private key, only known to them, to decrypt the message. If they use the key in this manner, they are using an asymmetric key. To implement this asymmetric key algorithm, the private key should be able to decrypt the message that was encrypted using the public key, and the private key should be impossible to derive from the public key. The Rivest, Shamir, and Adelson algorithm can be used to create a public and private key pair by using modular arithmetic. 

Message integrity and authentication are implemented by using a message digest. A message digest is created by applying a hash function to a message. The hash is then signed using their private key, thus creating the digital signature. The result is then send to the receiver. The receiver then uses the sender's public key to decrypt the digital signature. This shows the hash that the sender received when they ran it through their hash function. To confirm the sender's identity, the receiver runs the message through a hash function and compares it to the results of the hash when decrypted using the sender's public key. If these hash values match, the sender is authenticated and the integrity of the message is upheld.  

Overall, this week's concept of ciphers was a bit difficult to wrap my head around, especially after the midterm. I have experience with simple ciphers, having taught the subject in a math class. I noticed that I was confusing the process of encrptying and decrpyting a message with the process of authenticating the message and its integrity. I realized that these processes were separate with one coming before the other. The visuals in the reading really helped with understanding the process of authentication and message integrity.