A QR Code Based Zero-Watermarking Scheme for Authentication of Medical Images in Teleradiology Cloud

Algorithm 1

Master share and secret share creation.

  𝐈𝐧𝐩𝐮𝐭: Host Image 𝐇 of size 𝐍×𝐍, Watermark 𝐖 of size 𝐦×𝐦, Key (𝐤_𝐢,𝐤_𝐣) for initial block

    Selection, size of block 𝐛×𝐛, Number of iterations 𝐢 for Arnold Transform

  𝐎𝐮𝐭𝐩𝐮𝐭: Secret Share 𝐒𝐬𝐡𝐚𝐫𝐞 of size 𝐦×𝐦

Step  1. Apply Contourlet Transform on 𝐇 to generate a 𝐧×𝐧 LF subband

Step  2. Perform a 𝐛×𝐛 block partitioning on the LF subband to generate 𝐧/𝐛×𝐧/𝐛 non

   overlapping blocks

Step  3. Apply Arnold Transform on 𝐖 to generate scrambled watermark 𝐒𝐖

Step  4. Perform steps 4–9 for each bit 𝐖_𝐢𝐣 of watermark

Step  5. Apply Arnold transform on (𝐤_𝐢,𝐤_𝐣) to select a block for Master Share creation; Increment

    𝐤_𝐢 and 𝐤_𝐣 by 1; i.e., 𝐤_𝐢=𝐤_𝐢+1 and 𝐤_𝐣=𝐤_𝐣+1

Step  6. Apply SVD to the selected block to generate 𝐔,𝐒 and 𝐕 matrices

Step  7. Compute the Hu’s invariant moments 𝐈_𝟏,𝐈_𝟐 and 𝐈_𝟑 for the diagonal matrix 𝐒

Step  8. Create a 3 bit Master Share 𝐌𝐬𝐡𝐚𝐫𝐞 out of the sign bits of 𝐈_𝟏,𝐈_𝟐 and 𝐈_𝟑

Step  9. Encode 𝐌𝐬𝐡𝐚𝐫𝐞 and 𝐒𝐖 with equation (9) to generate Secret Share 𝐒𝐬𝐡𝐚𝐫𝐞, of size

    𝐦×𝐦; i.e. 𝐒𝐬𝐡𝐚𝐫𝐞=𝐟(𝐌𝐬𝐡𝐚𝐫𝐞,𝐒𝐖)