For indicating on a data medium (9) a sector referenced by a binary word (16) formed of a number M of first bytes each comprising a number L of bits, the method includes steps of etching onto the data medium locally at this sector a succession of M second bytes each corresponding to a first byte, each second byte being equal to a vector of N components, each with a value of +1 or −1, such that N=2L−1 and such that the scalar product of said vector with any other vector to which another second byte is equal, is at most equal to +1. The data medium (9) is, for example, an optical disk.