Secure method of exchanging information messages

A secure method of exchanging information messages sent successively from a sending platform to a receiving platform, which includes:

• a) an initialization sequence in which an initialization message containing information relating to a date t1 for sending a first information message M1 is exchanged between said sending platform and said receiving platform so that said sending platform and said receiving platform then know said date t1 for sending said first information message M1, and
• b) an information message transmission sequence in which:
• said information messages are sent successively by said sending platform at given time intervals ΔTE with a sending time tolerance δ based on a clock specific to said sending platform, so that said first message M1 is sent at said date t1 on said clock and the nth message Mn is sent at the date t1=t1+(n−1).ΔTE+δ, each message Mn being coded by means of a dynamic code Cn specific to said date tn of sending said message, and
• said messages received by said receiving platform are processed as a function of their reception date tr based on a clock specific to said receiving platform so that said messages received in an observation window Fn in the vicinity of tn are decoded using a decoding sequence DCn adapted to decode said dynamic code Cn, said clock of said receiving platform being synchronized to said date t1 on receiving said first message M1.