The invention relates to a secure data processing method comprising the steps of generating a first random value ; executing a first cryptographic algorithm using the first random value ; generating a second random value ; executing a second cryptographic algorithm using the second random value ; and generating a result to verify that the first algorithm was properly executed. Further aspects provide change of a resonant frequency of the prebuncher from a first frequency to a second frequency. The invention detects sequences of test sound frames having distortion levels that are greater than a temporal distortion threshold and calculates an average length and a maximum length of these sequences. The piercing needle has attached to it a securing tab of the ear tag. The sum of a depth of the first and second groove part and a sum of a depth of the third and fourth groove part are larger than a distance between the one principal surface and the other principal surface. The geodetic position of the source is determined from the detected seismic energy.