Iterated hash function Suppose that compress: 0, 1m>10, 1mis a compression function Preprocessing Given input x, x>=m+t+l, construct y using a public algorithm such that ly is a multiple of t For example: y=x pad(x) ety=yy21|..‖y 1<=i<=Fy|=t 1515 Iterated hash function Suppose that compress: {0,1}m+t → {0,1}m is a compression function. Preprocessing Given input x, |x| >= m+t+1, construct y using a public algorithm such that |y| is a multiple of t. For example: y = x || pad(x) Let y = y1 || y2 || … || yr, 1<=i<=r, |yi |=t