To interleave a binary sequence a represented by the polynomial.function..times..times. ##EQU00001## where n=R.M with R.gtoreq.M, i being an integer which may be written i=r.M+c, r and c being integers, r.gtoreq.0 and c .epsilon. [0, M-1], there is obtained, from the sequence a, an interleaved binary sequence a*. The interleaved binary data sequence a* represented by the polynomial.function..times..times. ##EQU00002## where i*=[r-h(c)].M+c mod n, the h(c) being obtained by the choice of an M-tuple h.sub.0=[h.sub.0(0), . . . , h.sub.0(M-1)] of non-negative integers less than R-1 such that, given a predetermined set .PI. of circulating matrices P of dimension M.times.M, for any matrix P of .PI., the residues modulo R of the components of the vector h.sub.0.P are not nil; and the corresponding choice of an M-tuple h obtained from h.sub.0 by the application of a permutation moving h.sub.0(c) to position L.times.c mod M, the integer L being relatively prime with M. (It is noted that the above underlining of the variables, and the above single bracketing, is in the original and is meant to be permanent.)