Improved Encrypted-Signals-Based Reversible Data Hiding Using Code Division Multiplexing and Value Expansion

Algorithm 1

Preprocess and signal encryption phase

Input:An original image with a size of , the number of spreading sequences , the expanded

parameter , and public key .

Output:The encrypted unit .

Step 1:Obtain the separated signals from the original pixel ,, which can be

calculated in Section 3.1. Define the embedded vector , and each pixel unit is represented

as .

Step 2:Modify to be by formula (14) for preventing overflow.

Step 3:Encrypt by and generate an encrypted unit .

Data embedding phase

Input:The encrypted unit , the number of spreading sequences , the expanded parameter , public key , and

secret bits.

Output:Marked unit .

Step 1:Divide secret bits into two parts and , where contains secret bits and contains the

remaining bits.

Step 2:Transform secret bits , in to using formula (9), and then obtain

the compound sequence for each unit .

Step 3:Encrypt by and denote it as .

Step 4:Embed into using CDM. By formula (10), obtain a new vector .

Step 5:Encode secret bits in to . is the decimal of for each unit .

Step 6:Encrypt by and denote it as .

Step 7:Embed into using VE. By formula (15), obtain a new signal . Then,

generate a marked unit .

Data extraction and image recovery phase

Input:The marked unit , the number of spreading sequences , the expanded parameter , and private key .

Output:Secret bits and the original image.

Step 1:Decrypt using to generate .

Step 2:Extract secret bits from by formulas (9) and (12).

Step 3:Obtain by extracting LSBs of .

Step 4:Calculate by formula (16) and recover by formula (17).

Step 5:Recover the original image by calculating .

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