1. A method of extraction of a key from a physical unclonable function using the states of cells of a volatile memory after a powering-on of this memory, wherein: cells are read according to addresses stored in a non-volatile memory; an error-correction code corrects the read states; and in case an error has been corrected, the address of the cell providing an erroneous state is replaced, in the non-volatile memory, with that of another cell providing the non-erroneous state, wherein the states extracted from the volatile memory are submitted to a mask to provide the key.