1. A method for determining that at least one object B is a candidate for near duplicate to an object A with a given similarity level th, comprising i) providing at least two different functions on an object, each function having a numeric function value; (ii) determining that at least one objects B is a candidate for near duplicate to an object A, if a condition is met, the condition includes: for any functions ƒ i from among said at least two functions, |ƒ i (A)-ƒ i (B)|≦δ i (ƒ,th), wherein δ i is dependent upon at least ƒ,th .