1. A method for using metadata to detect alteration of audio data, image data, or both, the method comprising: recording a first set of metadata characteristics for a first set of data representing original data, the first set of metadata characteristics including at least one respective semantic description for the first set of data; recording a second set of metadata characteristics for a second set of data representing data under test, the second set of metadata characteristics including at least one corresponding semantic description for the second set of data; and comparing the first and second sets of metadata characteristics wherein, if the first and second sets of metadata characteristics are not identical, then the second set of data is identified as an altered version of the first set of data.