Image Secret Sharing-Based Selective Encryption

Operating on the bit-levels of the secret image, encryption operations such as image secret sharing-based encryption can be selectively performed depending on the application constraints and/or user's needs. In this way, the encryption process alters only the selected bits while the remaining bits are kept unchanged. The figure on the left shows shares obtained respectively using no encryption and by encrypting the third most significant bit, the second most significant bit, the most significant bit, and the three most significant bits of each color component. The confidentiality increases with the significance of bits being encrypted. A sufficient level of protection of the visual information is achieved by encrypting the first two or three most significant bits. 

Another important factor in color image encryption is the color information. The figure on the right depicts share images generated when the encryption operations are selectively applied to the particular color channels. Images correspond respectively to no encryption, and the encrypted red, green, blue, red+green, red+blue, green+blue, and red+green+blue channels. As it can be seen from the presented example, encrypting either one or two color channels does not completely obscure the actual input. This suggests that for secure image secret sharing-based encryption, all the channels of the color RGB image should be encrypted.