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IADIS International Conference WWW/Internet 2010Table 2. The list of functions that are used in RIGFunction number Function name Function meaning12345678910111213141516X[]Y[]R[]Bw[G]Expf[a]Sin[a]Cos[a]Tan[a]Arctan[a]Reverse[a]Add[a,b]Mult[a,b]Div[a,b]RGB[r,g,b]If[cond,T,E]Mix[a,b,c,d]Identifies the X coordinate.Identifies the Y coordinate.Generates random number in range [-1,1]A shade of gray, G=-1 is black, G=1 is white.The exponential function.The sine function.The cosine function.The tangent function.The arctangent function.The reverse color of a.The sum of two colors.The product of two colors.The division of two colors.A color specified by the RGB component.The “ if -then-else” function: if cond is positive, then the value is T, else the value is E.The mixing of two colors a and b depending on the value of c and d.3.2 Linear Feedback Shift Registers (LFSR)The embedded image properties are described as set of bytes. These bytes must be composed in a randomform. A feedback shift register was used to satisfy the randomness.A feedback shift register is made up of two parts: a shift register and a feedback function as it is shownin Figure 1. The shift register contains a sequence of bits. The length of a shift register is figured in bits; if itis n bits long, it is called an n-bit shift register.The simplest kind of feedback shift register is a linear feedback shift register or LFSR as it is shown inFigure 2. The feedback function is simply the XOR of certain bits in the register; the list of these bits is calleda tap sequence.b n b n-1 …… b 4 b 3 b 2 b 1Feedback FunctionFigure 1. Feedback shift registerb n b n-1 …… b 4 b 3 b 2 b 1Shift Registerb n b n 1Feedback Functionb 4 b 3 b 2 b 1Figure 1. Feedback shift registerFigure 2. Linear Feedback shift registerOutput357