On 5/9/05, Sarad AV <jtrjtrjtr2001@yahoo.com> wrote:
If user A has the integer a and user B has the integer b, can a zero knowledge proof be developed to show that a>b,a<b or a=b.
You've got two different things mixed up here. A zero knowledge proof is normally used by one person to show that he knows a value satisfying certain conditions, without revealing what the value is. What you are asking for involves two people who want to compute a function of their inputs, without revealing those inputs. That is known as a multi party computation or MPC. As was pointed out, Schneier has some good pointers on MPC calculations. There is a program you can download called Fairplay which will perform MPC calculations like this. One of them does exactly what you are asking for. See http://www.cs.huji.ac.il/labs/danss/Fairplay/ CP