Design of a Cryptosystem for DCT Compressed Image Using Arnold Transform and Fractional Fourier Transform

摘要

The authors have proposed an image cryptosystem on the compressed version of the secret image to reduce the computational overhead and also to utilise the limited bandwidth of the communication channel maintaining the security. The compression has been done using transformation tool like discrete cosine transform (DCT). In the proposed scheme, the insignificant DCT coefficients of the secret image are discarded for compression of the secret image and the significant DCT coefficients are encrypted employing Arnold transformation (ACM) followed by fractional Fourier transform (FrFt). The parameters used in Arnold transformation and fractional Fourier transformation are kept confidential and considered as secret keys. The proposed scheme has been tested on a set of standard gray scale images and satisfactory results have been found. Besides, the security analysis has been carried out to demonstrate the effectiveness of the proposed scheme against some possible cryptographic attacks.