The invention relates to a method to verify that data received by a receiver has been sent by a transmitter authorized by a trusted third party, the transmitter and the receiver being connected to a digital network. An identifier is associated with the data sent by the transmitter and, on receipt of the data by the receiver, the receiver generates a random number and diffuses the same on the network. The transmitter that receives the random number calculates a response by applying a first function to the random number and to the identifier, and sends the response to the receiver which verifies the response received by applying a second function to the response received, the random number and the identifier. The first function is delivered first to the transmitter by the trusted third party. The second function is a function for checking the result of the first function which is delivered first to the receiver by the trusted third party.