A data transmission method uses at least two communication networks to exchange
data. The data transmission method on a first medium includes an operation for
opening a communication session on the first communication medium and during the
session, an operation for receiving confidential information on a single address
terminal on a second communication medium, and an operation or transmitting, on
the first communication medium, a confidential message representing the confidential
information and an operation for verifying whether the confidential message corresponds
to the confidential information.
