1. A computer-implemented method for storing an object, the method comprising: providing an object, an ordering vector of the object, the ordering vector being associated to a lexicographic order having at least one dimension, and base keys associated to each dimension of the lexicographic order; deriving a key by retrieving the base key associated to the first dimension of the lexicographic order for which the ordering vector has a value different from the smallest value, and applying a one-way function a number of times corresponding to the value of the ordering vector for the last dimension of the lexicographic order; encrypting the object with the key; and storing the object as encrypted; wherein the dimension of the lexicographic order is equal to 1, the ordering vector having a single value and a single base key being provided, and deriving the key comprises retrieving the single base key and applying to the single base key the one-way function a number of times corresponding to the single value of the ordering vector.