16.4. ElGamal Encryption Scheme

Try these first

1. 1.

   What is a public key in the ElGamal encryption scheme?

   Hint

   Think about who can use it and how.

2. 2.

   Briefly explain what ciphertext is.

   Hint

   What happens to the original message?

3. 3.

   What does a public key allow anyone to do?

   • Decrypt messages
   • Encrypt messages
   • Access private information

   Hint

   Consider who can access the public key.

4. 4.

   True or False: The ElGamal scheme requires both sender and receiver to be online at the same time.

   • True
   • False

   Hint

   Think about the flexibility that public keys provide.

5. 5.

   You are given a public key that we know is derived from a specific secret key. How might an attacker use this information to pose a threat, and what are the limits of their success?

   Hint

   Consider the implications of knowing the public key versus the private key.

6. 6.

   Explain how ElGamal could be attacked if the discrete logarithm problem were solved efficiently. What would be the implications for secure communications?

   Hint

   Think about the relationship between the strength of the problem and its impact on cryptographic processes.