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Playfair.java
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Playfair.java
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package cryptography.ciphers.playfair;
import java.awt.Point;
import cryptography.Mode;
public class Playfair {
private static char[][] charTable;
private static Point[] positions;
public static void main(String[] args) {
}
public static String playfair(String inputText, String key, Boolean replaceJI, final Mode mode) {
try {
inputText = inputText.toUpperCase();
key = key.toUpperCase();
String output = null;
createTable(key, replaceJI);
if (mode == Mode.ENCRYPT) {
output = encode(prepareText(inputText, replaceJI));
}
if (mode == Mode.DECRYPT) {
output = decode(inputText);
}
return output;
} catch (Exception e) {
return e.toString();
}
}
private static void createTable(String key, boolean changeJtoI) {
charTable = new char[5][5];
positions = new Point[26];
String s = prepareText(key + "ABCDEFGHIJKLMNOPQRSTUVWXYZ", changeJtoI);
int len = s.length();
for (int i = 0, k = 0; i < len; i++) {
char c = s.charAt(i);
if (positions[c - 'A'] == null) {
charTable[k / 5][k % 5] = c;
positions[c - 'A'] = new Point(k % 5, k / 5);
k++;
}
}
}
private static String prepareText(String s, boolean changeJtoI) {
s = s.toUpperCase().replaceAll("[^A-Z]", "");
return changeJtoI ? s.replace("J", "I") : s.replace("Q", "");
}
private static String encode(String s) {
StringBuilder sb = new StringBuilder(s);
for (int i = 0; i < sb.length(); i += 2) {
if (i == sb.length() - 1)
sb.append(sb.length() % 2 == 1 ? 'X' : "");
else if (sb.charAt(i) == sb.charAt(i + 1))
sb.insert(i + 1, 'X');
}
return codec(sb, 1);
}
private static String decode(String s) {
return codec(new StringBuilder(s), 4);
}
private static String codec(StringBuilder text, int direction) {
int len = text.length();
try {
for (int i = 0; i < len; i += 2) {
char a = text.charAt(i);
char b = text.charAt(i + 1);
int row1 = positions[a - 'A'].y;
int row2 = positions[b - 'A'].y;
int col1 = positions[a - 'A'].x;
int col2 = positions[b - 'A'].x;
if (row1 == row2) {
col1 = (col1 + direction) % 5;
col2 = (col2 + direction) % 5;
} else if (col1 == col2) {
row1 = (row1 + direction) % 5;
row2 = (row2 + direction) % 5;
} else {
int tmp = col1;
col1 = col2;
col2 = tmp;
}
text.setCharAt(i, charTable[row1][col1]);
text.setCharAt(i + 1, charTable[row2][col2]);
}
} catch (Exception e) {
return "Bad key or setting!";
}
return text.toString();
}
}