An extended secret sharing scheme for colour images with fixed pixel expansion

An extended visual secret sharing scheme uses multiple innocent-looking cover images to hide a secret image such that none discloses any portion of the secret. In this article, an extended secret sharing technique is proposed that shares a secret colour image in a couple of significant images using a fixed pixel expansion factor of 9 for a colour space as large as comprising 224, i.e. 16 million colours approximately. Furthermore, the data hiding technique employed in this article uses all three planes of a colour image which reduces the number of cover images that would otherwise be needed. Recovery is performed through a simple stacking (XOR) operation and a sequence of random integers.