Abstract: An encrypted signature S representative of the information and of the identity of the holder of the information is established by means of a calculation algorithm for the encryption and the compression of the information to be saved. The signature S is recorded on the medium carrying the information forming the message M. The parameters for the calculation of the signature S, one or several secret keys, are recorded on at least one inviolable carrying medium. The application is to qualitative safeguarding and protection of data, on-line or not, in data bases.

Abstract: A psuedo-random interleaving method suitable for use in transmitting digital data. A pseudo-random pilot sequence is used for simultaneously reading from and writing to a vector of size Tv.gtoreq.Tc.times.Lm, the pilot sequence satisfying a minimum distance law Lm, except when blocking occurs. Deinterleaving is performed symmetrically by means of an inverse pilot sequence suitable for reconstituting successive code words.

Abstract: A videotex asynchroneous transmission system uses a parity bit for each character, with a continuous ARQ-type retransmission method. The data are transmitted in blocks (so-called "code words"). Each code word is comprised of a block of seventeen bytes "1"-"15" constituting the characters which are to be transmitted encoded by seven bits b1-b7. The 8th bit b8 of each byte is the parity bit. The 16th byte is the check byte of the code word, and the 17th byte being the enabling byte of the code word.