answer final question of part 1

1 files changed, 25 insertions, 7 deletions

diff --git a/doc/assignment4.md b/doc/assignment4.md
index 2eb22b7..f871097 100644
--- a/doc/assignment4.md
+++ b/doc/assignment4.md
@@ -3,13 +3,6 @@
 
 Assignment 4
 
-This assignment should be submitted after you have finished Unit 5.
-It is worth 15% of your final grade for this course.
-
-## Part 1: Concepts (20 marks; 4 marks each)
-
-Please answer the following questions in complete sentences. Your answer for each question should be about 150 words.
-
 1. Why is it important to distinguish between mechanisms of protection and policies of protection?
 
   Protection mechanisms are used to constrain the potential senders and/or
@@ -63,4 +56,29 @@ Please answer the following questions in complete sentences. Your answer for eac
   system crashes and program malfunctions.
 
 1. What is the difference between symmetric encryption and asymmetric encryption?
+
+  Symmetric encryption relies on a single shared key for performing both the
+  encryption an decryption operations.
+
+  Asymmetric encryption algorithms rely on each party having both a public and
+  private key. Public keys are exchange so that plaintext can be encrypted into
+  ciphertext using the other party's public key. Only that party can decrypt
+  the ciphertext back into plaintext using their private key.
+
+  Symmetric encryption and decryption operations tend to operate faster than
+  their asymmetric encryption counterparts. So many protocol will use asymmetric
+  encryption to perform the initial handshake to exchange a shared session key
+  to perform the remaining operations using the shared session key.
+
 1. What are the two main varieties of authentication algorithms?
+
+  Message-authentication code (MAC) is a form of an authentication algorithm
+  that uses symmetric encryption. This algorithm generates a checksum using
+  the message data and key as input. On the receiving end the checksum and key
+  can be used to verify the authenticity of the data received.
+
+  The second type of authentication algorithm is a digital signature.
+  Digital signatures utilize asymmetric encryption by encrypting a
+  digest of the plaintext data using their own private key. This allows the
+  receiving party to decrypt the digest using the senders public key to verify
+  the authenticity of the data.