A Blind Reversible Robust Watermarking Scheme for Relational Databases

Algorithm 2

Watermark embedding.

Input: Relational database 𝑅, attribute 𝐴_𝑗, parameter 𝑔

Output: Watermarked relational database 𝑅_𝑊, Mid, and two pairs, that is,

    (PP₁, CZP₁) and (PP₂, CZP₂)

(1)      𝑆 = Tuple_Selection(𝑅,𝐾,𝑔)

(2)      foreach tuple 𝑞∈𝑆 do

(3) attribute_index 𝑗=𝐹(𝑞.𝑃𝐾) mod 𝛼 // selected attribute 𝐴_𝑗

(4) mark_bit imb = 𝐹(𝑞.𝑃𝐾) mod 𝐿 // determine mark bit

(5) 𝑇 = Get2digits(𝐴_𝑗);

(6) insert 𝑇 into Seq;

(7) insert imb into Mark_Seq; //save index of the corresponding mark bit

(8)      end foreach;

(9)      Mid = GetMid(Seq);

(10) Dif_Seq = Diff(Seq, Mid);

(11) determine two pairs (PP₁, CZP₁) and (PP₂, CZP₂);

(12) generate the watermark data 𝑊; //using (4)

(13) for 𝑖=0 to 𝐷𝑖𝑓_𝑆𝑒𝑞 − 1 do

(14) if Dif_Seq[𝑖] = PP₂, then

(15) 𝑏 = W[Mark_Seq[𝑖]]; //read the corresponding mark bit from 𝑊

(16) Dif_Seq[𝑖] = Dif_Seq[𝑖] + 𝑏;

(17) else

(18)           if Dif_Seq[𝑖] < CZP₂ and Dif_Seq[𝑖] > PP₂ then

(19) Dif_Seq[𝑖] = Dif_Seq[𝑖] + 1;

(20)           end if;

(21)       end if;

(22)       if Dif_Seq[𝑖] = PP₁, then

(23) 𝑏 = 𝑊[Mark_Seq[𝑖]]; //read the corresponding mark bit from 𝑊

(24) 𝐷𝑖𝑓_𝑆𝑒𝑞[𝑖]=𝐷𝑖𝑓_𝑆𝑒𝑞[𝑖]−𝑏;

(25)       else

(26)           if Dif_Seq[𝑖] > CZP₁ and Dif_Seq[𝑖] < PP₁ then

(27) Dif_Seq[𝑖] = Dif_Seq[𝑖] − 1;

(28)           end if;

(29)      end if;

(30) end for;

(31) Reflect_Update_Att(Diff_Seq, 𝐴_𝑗);