Abstract: The transmission method comprises: a step in which the vehicle obtains, from a distribution entity, a plurality of series of numbers each containing a base gi, a prime number pi, a first key Zi, wherein Zi=gizi modulo pi, wherein zi is a secret number, an associated validity number Vi, and stores in memory the N series of numbers; a step of generating a random number a; a step of calculating a second key KaZi wherein KaZi=Zia modulo pi; a step of creating a message M, during which the vehicle A inserts in the message M the validity number Vi; the second group of numbers a, pi and gi encrypted by means of the first key (Zi), in a header of the message, and the data, in a body of the message; and the vehicle performs a cryptographic operation on the message M using the second key (KaZi); and a step of transmitting the message M created by the vehicle through a radio communication channel.