Let wavelet authenticate and tent-map encrypt: a sacred connect against a secret nexus

To safeguard the content from malicious devices and users and to provide authentication and security to the transmitted content, it becomes mandatory to devise a combined watermarking and encryption algorithm. This paper addresses this concern by developing an algorithm to authenticate and encrypt the image before transmitting it safely. The algorithm was established using a watermarking technique. The watermarking was done by transforming the image into coefficients and embedding it in high-frequency components. The watermarked image was encrypted using a key generated using a combined logistical tent map and converted to DNA sequences. The sequences are stored and transmitted as such. At the receiver end, the image was recovered and de-watermarked. The label used for the watermark was compared with the obtained watermark at the receiver end. The proposed algorithm conforms to the required CIA triad (confidentiality, integrity, availability). The algorithm was tested for images in the Standard Test images database. On average, for an encrypted image, the peak signal to noise ratio (PSNR) was 9.1934 dB and had an entropy of 7.999 bits. The correlation coefficient of 0.0001, 0.0019, and 0.0003 for horizontal, vertical and diagonal directions was obtained. The watermark could be satisfactorily recovered from the cover, even with the addition of noise. The extracted watermark had a PSNR above 30 dB, with normalized cross-correlation (NCC) above 0.9, bit error rate (BER) below 0.1 and structural similarity index metric (SSIM) above 0.9. These results make the proposed algorithm suitable for authentication and encryption.