A method for allowing a first party and a second party to obtain shared secret information is provided. The method comprises the steps of: obtaining, by the first party, a sequence of values A=X+NA where X is a sequence of values and NA is a random sequence associated with the first party; obtaining, by the second party, a sequence of values B=X+NB where NB is a random sequence associated with the second party; performing, by the first and second parties, a data matching procedure to identify corresponding pairs of values, a, b, in respective sequences A and B that match, wherein sequences A and B are discrete-valued sequences equal to, derived from, or derived using, sequences A and B; wherein the shared secret information is equal to, or derived from, or derived using, the matching values in sequences A and B.