“…Our algorithm, instead, slightly modifies an existing alpha channel, and thus has a wider range of applications to images of any kind. The advantage of [20] is an authentication at the pixel level, whilst ours, as well as [21], is at the block level: nonetheless, when [20] uses three bits to authenticate every single pixel, the probability of not detecting an attack to a pixel is 12.5% (i.e., 1/2 3 ).…”