1. A method of identifying an RF label in an RF label identification system comprising an RF label reader and a plurality of RF labels, a unique and secret identifier being associated with each of said RF labels; said method comprising the following steps: /a/ sending a first random number from an RF label to the RF label reader; /b/ sending a second random number from the RF label reader to the RF label; /c/ in said RF label, encrypting the identifier of the label by executing the following steps consisting of: generating third and fourth random numbers in accordance with a probabilistic rule; transforming said first and second random numbers in accordance with a determined function and obtaining respective first and second transformed numbers; obtaining a value of the encrypted identifier by combining the identifier of the label with the first and second random numbers, with the first and second transformed numbers, and with the third and fourth random numbers; /d/ sending from the RF label to the RF label reader the value of the encrypted identifier resulting from the step /c/; /e/ repeating the steps /a/ to /d/ N times, N being an integer; /f/ identifying said RF label in a list of label identifiers in the label reader by determining the associated identifier as a function of N values of the encrypted identifier received, of the determined function, of the N first and second random numbers and of the probabilistic rule.