第4章 信息理论《密码学：加密演算法》(邓安文)(免费).pptx

1.2 20061.3 20061.4 2006Sp:2 S2M|MSp(A)0ASp(S)1p(AB)p(A)p(B)AB1.5 2006p()0 ABp(A)p(B)0p(A)1ASp(S A)1p(A) 12nAAA、 、nniii 1i 1p(A )p(A )a Ap(A)p(a)p(a)p(a)1.6 2006p(B)0p(AB)p(A|B)p(B)p(AB)p(A)p(B)p(A | B)p(A)1.7 2006p(A)0p(B)0p(B)p(A|B)p(A)p(B|A)p(A|B)p(B)p(AB)p(B|A)p(A)p(AB)p(B)p(A|B)p(A)p(B|A)1.8 2006p(m|c)p(m)#CKp(m)0kE (m)c1.9 20062x AH(X)p(Xx)log (p(Xx) X Y2X Y(x,y) A BH(X,Y)p(x,y)log (p(x,y) 1.10 2006Xx AXY2Yx Ay BX Y2Y(x,y) A BH(Y|X)p (x)H(Y|Xx)p (x)p (y| x)log p (y| x)p(x,y)log p (y| x) 。1.11 2006H(X,Y)H(X)H(Y|X)X Y2X Y(x,y) A BH(X,Y)p(x,y)log p(x,y) X Y2XY(x,y) A Bp(x,y)log p (x)p (y| x) X Y2X(x,y) A Bp(x,y)log p (x) X Y2Y(x,y) A Bp(x,y)log p (y| x) 2XX Yx Ay Blog p (x)p(x,y)H(Y|X) X2Xx Ap (x)log p (x)H(Y|X) X YXy Bp(x,y)p (x)H(X)H(Y|X)1.12 2006H(X)log2| A |H(X,Y)H(X)H(Y)H(Y | X)H(Y)H(M |C)H(M)1.13 2006H(K |C)H(K)H(M)H(C)H(K,M,C) = H(M,K) + H(C|M,K)H(M,K) (H(C|M,K)=0)H(K)H(M)H(K,M,C) = H(K,C) + H(M|K,C)H(K,C) (H(M|K,C)=0)H(C)H(K |C)H(K |C)H(K,C)H(C)H(K)H(M)H(C)1.14 2006ncCk(c): k|E (m)KnLnH()HlimnM ML2HR1log | M M1.15 2006Unicity距离n0估计为：202log |nRlog |K KM M1.16 2006202log 26n1.330.75log 26202log 312n2.350.75log 26n202log 2n1.33nn0.75log 2