16.5.1. Overview of RSA

Try these first

1. 1.

   What does RSA stand for?

   Hint

   Think of the names of the three inventors.

2. 2.

   What is the purpose of a public key in RSA?

   Hint

   Which key does the other person use to lock the message?

3. 3.

   What is the primary security feature of RSA?

   • Factoring large primes
   • Substitution ciphers
   • Symmetric key encryption

   Hint

   Think about what keeps the door locked.

4. 4.

   True or False: The public key is kept secret.

   • True
   • False

   Hint

   Think about which key is like an open door.

5. 5.

   You are given N = 221 and e = 5. Factor N, find ϕ(N), and determine d if you need d to be coprime to ϕ(N).

   Hint

   Use the Euclidean algorithm to find d.

6. 6.

   Explain why using larger key sizes (e.g., 2048 bits) enhances RSA security. Include potential vulnerabilities of smaller key sizes.

   Hint

   Consider how computational power affects cryptotherapy.