破译密码问题比较难,且有些神秘,许多同 学感到可望不可及.下面举三道典型例题,以探 索此类问题的规律和方法. 例1 现代社会对破译密码的难度要求越 来越高.有一种密码把英文的明文(真实文)按字 母分解,其中英文的a,b,c,…,z这26个字母(不 区分大小写)依次对应1,2,3,…,26这26个自然 数,如表1: It is difficult to decipher the password problem, and some are mysterious. Many students feel hopelessly unreachable. Here are three typical examples to explore the laws and methods of such problems. Example 1 Modern society is increasingly demanding the difficulty of deciphering passwords. There is a password that divides the English plain text (authentic text) into letters, in which the 26 letters (case-insensitive) of a, b, c, ..., z in English correspond to 1, 2, 3,..., 26 in this order. Natural numbers, as shown in Table 1: