Information Security Problem

Hashes can be used in online-bid systems. That is, instead of submitting the actual bits, each customer submits the hash of the bid. This can prevent people from seeing other people's bids and placing a bid just a little bit higher to win the bid.

a. What are the 2 properties of a secure hash function h that this scheme relies on to prevent cheating? Explain your answer (each is worth 1 pts for the name of the property and for explanation).

b. Outline a potential attack on this scheme (hint: when buying/bidding on something, people probably know the range of the price).