1. What are the properties of hash functions?
3. Bob designed a new scheme to detect whether a message is modified by an attacker
(protecting data integrity). The scheme is to append to each message a SHA-256 hash of
that message. Explain the vulnerability of Bob’s design
4. Bob designed another new scheme to detect whether a message is modified by an
attacker (protecting data integrity). The scheme is to append to each message a SHA256
hash of that message, then encrypt the whole appended message using AES with a known
key to the public. Explain the vulnerability of Bob’s design.
5. A company is selling an artifact worth millions of dollars. Many interested buyers are in
the bidding process, which works as follows. Each buyer sends the information of his/her
final number (e.g., $1,000,000.00) to the company to show his/her commitment. And the
number must be kept confidential from other buyers and even the company before the
deadline. After the deadline, all numbers are released to all buyers and the company, then
the buyer with the highest number wins. Design a HASH FUNCTION based scheme to
secure the bidding process. Describe steps a buyer and/or the company should do
Before deadline.