Problem (1)

- Alice, Bob and Charlie have a secret key a=3, b=4, c=5, respectively.

- They want to find a common secret key using Diffie-Hellan key exchange protocol (with g=2, p=5).

- Assume that there is no man-in-the-middle attacker.

-  Show how they can share a common secret key with the above mentioned numbers.  

Problem (2)

- Encrypt and decrypt first 3 characters of your last name (family name) using RSA with the prime numbers (p=7, q=11). (If your last name is shorter than 3 characters, use first 3 characters of your first name instead.)

- Use ASCII code at: ascii.cl

• e.g.) Michael Nordan
• A=65, B=66, ...
• N -> 78, o->111, r->72

- You can choose an encryption key e among {11, 13, 19, 23, 29} and find d.

- You have to show the all the steps (in particular, EEA) as detail as possible.

- Encrypt the message using your encryption key e like this way (n=pq):

If you number is greater than 76, decompose them into a smaller number as follows.

• e.g., 7 8 11 17 2
• (7^e) mod n
• (8^e) mod n
• (11^e) mod n
• (17^e) mod n
• (2^e) mod n

- Decryption the ciphertext using private key d.