Reversible Fragile Watermarking Scheme for Relational Database Based on Prediction-Error Expansion

Algorithm 4

Watermark detection.

(1)	Hp = HMAC (Ks ||h1||h2||…||hµ||Ks)   //Hashing of primary key hash values
(2)	for each attribute Ajdo
(3)	for each tuple tido
(4)	lsd = GetLSD (ti.Aj)
(5)	T = MSD (ti.Aj)
(6)	= lsd−hi   //watermarked prediction error
(7)	[i] = LSB ()   //recovering embedded bit
(8)	ti.Aj = RecoverData (T, lsd, , Wj∗[i])   //See Algorithm5
(9)	end for
(10)	Hj = HMAC (Hp ||t1.Aj||t2.Aj||…||tµ.Aj||Ks)   //attribute hash
(11)	//Generate watermark bits
(12)	Wj = µ MSB (Hj)   //Assume length (Hj) ≥ µ
(13)	//Check integrity
(14)	if Wj ≠  then
(15)	attribute Aj not authentic
(16)	end if
(17)	end for