Abstract: The invention relates to methods for processing data packets according to a set of rules, and especially for preparing of decision trees for selecting the correct rule for processing of a data packet. In preparation of a decision tree, a splitting point within a dimension being studied is chosen as follows. The rules are sorted to allow monotonous iteration through all range end values specified in the rules in the dimension being studied. The range end values are then iterated through in a monotonous fashion, either increasing or decreasing. At each iteration, the number of range low end values and the number of range high end values being equal to the current iteration value is counted. From these counts and the accumulated results from the corresponding counts in previous iterations, the numbers of rules with ranges in different positions relative to the current iteration value are deduced, and from these values, the goodness of the iteration value is calculated.

Abstract: According to the invention, the problem of checking the identity of others is alleviated by creating a mechanism, which allows users to trust and utilize the checking work performed by certain other users, so that every user need not check and confirm the identity of every other user. This can be accomplished by allowing a user who has checked that the identity of a number of other users truly correspond to their certificates, produce a list of these checked certificates, so that other users can import the list of checked certificates into their systems.