  During the recent years, tampering of digital images has become a general
habit among people and professionals. As a result, establishment of image
authenticity has become a key issue in fields those make use of digital images.
Authentication of an image involves separation of original camera outputs from
their tampered or Stego counterparts. Digital image cloning being a popular
type of image tampering, in this paper we have experimentally analyzed seven
different algorithms of cloning detection such as the simple overlapped block
matching with lexicographic sorting (SOBMwLS) algorithm, block matching with
discrete cosine transformation, principal component analysis, discrete wavelet
transformation and singular value decomposition performed on the blocks (DCT,
DWT, PCA, SVD), two combination models where, DCT and DWT are combined with
singular value decomposition (DCTSVD and DWTSVD. A comparative study of all
these techniques with respect to their time complexities and robustness of
detection against various post processing operations such as cropping,
brightness and contrast adjustments are presented in the paper.
