Columnar Transposition Cipher with example usage

Author: freitzzz

ciphers/ColumnarTranspositionCipher.java

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+/**
+ * Columnar Transposition Cipher Encryption and Decryption.
+ * @author <a href="https://github.com/freitzzz">freitzzz</a>
+ */
+public class ColumnarTranspositionCipher {
+    private static String keyword;
+    private static Object[][] table;
+    private static String abecedarium;
+    public static final String ABECEDARIUM="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789,.;:-@";
+    private static final String ENCRYPTION_FIELD="≈";
+    private static final char ENCRYPTION_FIELD_CHAR='≈';
+    /**
+     * Encrypts a certain String with the Columnar Transposition Cipher Rule
+     * @param word Word being encrypted
+     * @param keyword String with keyword being used
+     * @return a String with the word encrypted by the Columnar Transposition Cipher Rule
+     */
+    public static String encrpyter(String word,String keyword){
+        ColumnarTranspositionCipher.keyword=keyword;
+        abecedariumBuilder(500);
+        table=tableBuilder(word);
+        Object[][] sortedTable=sortTable(table);
+        String wordEncrypted="";
+        for(int i=0;i<sortedTable[0].length;i++){
+            for(int j=1;j<sortedTable.length;j++){
+                wordEncrypted+=sortedTable[j][i];
+            }
+        }
+        return wordEncrypted;
+    }
+
+    /**
+     * Encrypts a certain String with the Columnar Transposition Cipher Rule
+     * @param word Word being encrypted
+     * @param keyword String with keyword being used
+     * @param abecedarium String with the abecedarium being used. null for default one
+     * @return a String with the word encrypted by the Columnar Transposition Cipher Rule
+     */
+    public static String encrpyter(String word,String keyword,String abecedarium){
+        ColumnarTranspositionCipher.keyword=keyword;
+        if(abecedarium!=null){
+            ColumnarTranspositionCipher.abecedarium=abecedarium;
+        }else{
+            ColumnarTranspositionCipher.abecedarium=ABECEDARIUM;
+        }
+        table=tableBuilder(word);
+        Object[][] sortedTable=sortTable(table);
+        String wordEncrypted="";
+        for(int i=0;i<sortedTable[0].length;i++){
+            for(int j=1;j<sortedTable.length;j++){
+                wordEncrypted+=sortedTable[j][i];
+            }
+        }
+        return wordEncrypted;
+    }
+    /**
+     * Decryps a certain encrypted String with the Columnar Transposition Cipher Rule
+     * @return a String decrypted with the word ecrypted by the Columnar Transpositiion Cipher Rule
+     */
+    public static String decrypter(){
+        String wordDecrypted="";
+        for(int i=1;i<table.length;i++){
+            for(int j=0;j<table[i].length;j++){
+                wordDecrypted+=table[i][j];
+            }
+        }
+        return wordDecrypted.replaceAll(ENCRYPTION_FIELD,"");
+    }
+    /**
+     * Builds a table with the word to be encrpyted in rows by the Columnar Transposition Cipher Rule
+     * @return An Object[][] with the word to be encrypted filled in rows and columns
+     */
+    private static Object[][] tableBuilder(String word){
+        Object[][] table=new Object[rows(word)+1][keyword.length()];
+        char[] wordInChards=word.toCharArray();
+        //Fils in the respective numbers
+        table[0]=findElements();
+        int charElement=0;
+        for(int i=1;i<table.length;i++){
+            for(int j=0;j<table[i].length;j++){
+                if(charElement<wordInChards.length){
+                    table[i][j]=(char)wordInChards[charElement];
+                    charElement++;
+                }else{
+                    table[i][j]=ENCRYPTION_FIELD_CHAR;
+                }
+            }
+        }
+        return table;
+    }
+    /**
+     * Determines the number of rows the table should have regarding the Columnar Transposition Cipher Rule
+     * @return an int with the number of rows that the table should have in order to respect the Columnar Transposition Cipher Rule.
+     */
+    private static int rows(String word){
+        if((double)word.length()/keyword.length()>word.length()/keyword.length()){
+            return (word.length()/keyword.length())+1;
+        }else{
+            return word.length()/keyword.length();
+        }
+    }
+    private static Object[] findElements(){
+        Object[] charValues=new Object[keyword.length()];
+        for(int i=0;i<charValues.length;i++){
+            for(int j=0;j<abecedarium.length();j++){
+                if(keyword.charAt(i)==abecedarium.charAt(j))charValues[i]=j;
+            }
+        }
+        return charValues;
+    }
+    private static Object[][] sortTable(Object[][] table){
+        Object[][] tableSorted=new Object[table.length][table[0].length];
+        for(int i=0;i<tableSorted.length;i++){
+            for(int j=0;j<tableSorted[i].length;j++){
+                tableSorted[i][j]=table[i][j];
+            }
+        }
+        for(int i=0;i<tableSorted[0].length;i++){
+            for(int j=i+1;j<tableSorted[0].length;j++){
+                if((int)tableSorted[0][i]>(int)table[0][j]){
+                    Object[] column=getColumn(tableSorted,tableSorted.length,i);
+                    switchColumns(tableSorted,j,i,column);
+                }
+            }
+        }
+        return tableSorted;
+    }
+    private static Object[] getColumn(Object[][] table,int rows,int column){
+        Object[] columnArray=new Object[rows];
+        for(int i=0;i<rows;i++){
+            columnArray[i]=table[i][column];
+        }
+        return columnArray;
+    }
+    private static void switchColumns(Object[][] table, int firstColumnIndex,int secondColumnIndex,Object[] columnToSwitch){
+        for(int i=0;i<table.length;i++){
+            table[i][secondColumnIndex]=table[i][firstColumnIndex];
+            table[i][firstColumnIndex]=columnToSwitch[i];
+        }
+    }
+    /**
+     * Creates an abecedarium with a specified ascii inded
+     * @param value Number of characters being used based on the ASCII Table
+     */
+    private static void abecedariumBuilder(int value){
+        abecedarium="";
+        for(int i=0;i<value;i++){
+            abecedarium+=(char)i;
+        }
+    }
+    private static void showTable(){
+        for(int i=0;i<table.length;i++){
+            for(int j=0;j<table[i].length;j++){
+                System.out.print(table[i][j]+" ");
+            }
+            System.out.println();
+        }
+    }
+    public static void main(String[] args){
+        String keywordForExample="asd215";
+        String wordBeingEncrypted="This is a test of the Columnar Transposition Cipher";
+        System.out.println("### Example of Columnar Transposition Cipher ###\n");
+        System.out.println("Word being encryped ->>> "+wordBeingEncrypted);
+        System.out.println("Word encrypted ->>> "+ColumnarTranspositionCipher.encrpyter(wordBeingEncrypted,keywordForExample));
+        System.out.println("Word decryped ->>> "+ColumnarTranspositionCipher.decrypter());
+        System.out.println("\n### Encrypted Table ###");
+        showTable();
+    }
+}