A Robust Coverless Image Steganography Algorithm Based on Image Retrieval with SURF Features

Algorithm 1

Secret Information Hiding.

	Input: Secret information S, sorted image database IMG,
	Output: Stego image
(1)	Divide S into segments:
(2)	Generate multiple sub-CIDs I =  using sorted image database IMG and Key
(3)	for k = 1: do
(4)	Generate a hash sequence for each image based on the order of the sequence
(5)	end for
(6)	Update image index database
(7)	for i = 1: n do
(8)	Search for
(9)	When has already been used
(10)	end for
(11)	Record the number of zero fillings and map it to the last image
(12)	Get stego images set and transmit them to the receiver
(13)	end.