用矩阵的行列式说明此密码不具真实性?!
Consider the following algorithm for encoding alphabetical messages.Step 1:Break the message(including spaces) into 4 letter blocks.
Step 2:Convert each 4 letter block into a 4*1 vector d(i),using:
space=0 , a=1, b=2,...,z=26.
Step 3:Encode each block by computing Ad(i) ,where A is a 4*4 matrix.
Step 4:Present the encoded message as a numerical sequence,where the first four terms of the sequence are the entries in Ad(1),reading from the top down ,teh second four are the entries in Ad(2),etc.
(注意:已知det(A)=-6)
Q1>,Convert the following already coded message into a 4*4 matrix B:
1, 0, -3, 0, -3, -25, 0, 5, -13, 5 ,41, 0, 36, -31, 42, 35.
Then find det(B) using the co-factor method only, show all working
(这一问我已求出答案:det(B)=3885)
Q2>,Use your result from Q1(即det(B)=3885) and det(A) and NOTHING ELSE to show the message in Q1> cannot be genuine.
[[i] 本帖最后由 semigroups 于 2007-5-19 13:45 编辑 [/i]] 翻译成中文看看
看见英语就头晕
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