Взлом Vigenere cipher — различия между версиями

 1 def encryption(plaintext, keyword):
 2     txt_len = len(plaintext)
 3     keyword *= txt_len // len(keyword) + 1
 4     keyword = keyword[:txt_len]
 5     encoded = ""
 6     for c in range(txt_len):
 7         newchar = ord(plaintext[c]) + ord(keyword[c]) - 194
 8         newchar %= 25
 9         encoded += chr(newchar + 97)
10     return encoded

1 def decrypt(key, ciphertext):
2     from itertools import cycle
3     ALPHA = 'abcdefghijklmnopqrstuvwxyz'
4     pairs = zip(ciphertext, cycle(key))
5     result = ''
6     for pair in pairs:
7         total = reduce(lambda x, y: ALPHA.index(x) - ALPHA.index(y), pair)
8         result += ALPHA[total % 26]
9     return result

 1 module VigenereCipher
 2  
 3   BASE = 'A'.ord
 4   SIZE = 'Z'.ord - BASE + 1
 5  
 6   def encrypt(text, key)
 7     crypt(text, key, :+)
 8   end
 9  
10   def decrypt(text, key)
11     crypt(text, key, :-)
12   end
13  
14   def crypt(text, key, dir)
15     text = text.upcase.gsub(/[^A-Z]/, '')
16     key_iterator = key.upcase.gsub(/[^A-Z]/, '').chars.map{|c| c.ord - BASE}.cycle
17     text.each_char.inject('') do |ciphertext, char|
18       offset = key_iterator.next
19       ciphertext << ((char.ord - BASE).send(dir, offset) % SIZE + BASE).chr
20     end
21   end
22  
23 end

 1     static String encrypt(String text, final String key) {
 2         String res = "";
 3         text = text.toUpperCase();
 4         for (int i = 0, j = 0; i < text.length(); i++) {
 5             char c = text.charAt(i);
 6             if (c < 'A' || c > 'Z') continue;
 7             res += (char)((c + key.charAt(j) - 2 * 'A') % 26 + 'A');
 8             j = ++j % key.length();
 9         }
10         return res;
11     }

 1     static String decrypt(String text, final String key) {
 2         String res = "";
 3         text = text.toUpperCase();
 4         for (int i = 0, j = 0; i < text.length(); i++) {
 5             char c = text.charAt(i);
 6             if (c < 'A' || c > 'Z') continue;
 7             res += (char)((c - key.charAt(j) + 26) % 26 + 'A');
 8             j = ++j % key.length();
 9         }
10         return res;
11     }