Abstract: A method for secure identification of stations connected over data communications networks during a transaction, comprising transmitting, on the part of a first station to a second station, an identification index of a reference cell in a sequence of codes known to both stations and a first code in the sequence and chosen according to a first criterion known to both stations; identifying, by the second station, a cell in the sequence through the received index; verifying the first code by the second station; transmitting, by the second station toward the first station, a second code, in the series of codes calculated according to a second criterion known to both stations; verifying by the first station, the correctness of the second code; marking, by the first station and preferably also by the second station, the indices related to the codes that have been used as unusable for subsequent transactions.