PROGRAM : [COLUMNAR.java]

import java.io.*;

import java.util.*;

public class columnar

{ public String encrypt(String key,String message)

{ char[] c = key.toCharArray(); char temp;

String ciphertext = ""; Arrays.sort(c);

int keyl = key.length(); int x;

for(int i=0; i< keyl; i++)

{ x = key.indexOf(c[i]); //System.out.println(x);

for(int j=0 ; j< message.length()/keyl; j++)

{ ciphertext = ciphertext + message.charAt((x+ (j*keyl))); }

}return ciphertext;

}

public String decrypt(String key,String ciphertext)

{ String text = ""; int x; char[] c = key.toCharArray();

String ptext = ""; Arrays.sort(c);

String text1 = "";

for(int i=0; i<(ciphertext.length()/key.length()); i++)

{ for(int j=i;j< ciphertext.length(); j++)

{ text = text + ciphertext.charAt(j);j += (ciphertext.length()/key.length())-1;

}}

//System.out.println(text); char[] ptext1 = new char[key.length()]; int j=0;

for(int i=0; i< ciphertext.length()/key.length(); i++)

{ text1 = text.substring((j*key.length()),((j+1)*key.length()));

//System.out.println(text1);

for(int k=0; k < text1.length(); k++)

{ ptext1[key.indexOf(c[k])] = text1.charAt(k); } j++;

for(char v : ptext1) ptext = ptext + v;

}// System.out.println(ptext);

while(true)

{ if(ptext.charAt(ptext.length()-1) == 'x') ptext = ptext.substring(0,ptext.length()-1); else break;}

return ptext; }

public static void main(String[] args)throws IOException

{

BufferedReader b = new BufferedReader(new InputStreamReader(System.in));

System.out.println("Please enter the key :");

String key = b.readLine();

int keylength = key.length();

System.out.println("Please enter the message to be encrypted :");

String message = b.readLine();

int mess_length = message.length();

if(mess_length%keylength !=0)

{ for(int i=0; i< keylength - (mess_length%keylength); i++)

{ message = message + 'x'; } }

columnar c = new columnar();

System.out.println("Ciphertext is :"+ c.encrypt(key,message));

System.out.println("Please enter the ciphertext :");

String ctext = b.readLine();

System.out.println("The Plaintext for ["+ctext+"] is "+c.decrypt(key,ctext));

}

}

OUTPUT :

PROGRAM : [RAILFENCE.java]

import java.io.*;

import java.util.*;

public class railfence

{ public String message = ""; public BufferedReader b ; public int key;

private int rounds;

private String encryption()throws IOException

{ System.out.println("Please enter the message :");

b = new BufferedReader(new InputStreamReader(System.in));

message = b.readLine(); System.out.println("Please enter the key:");

key = Integer.parseInt(b.readLine()); String s="";

if(key==0 || key==1){ System.out.println("Please try again !"); System.exit(0);}

String ciphertext="";

if(key==2)

{ for(int i=0;i< message.length();i++)

{ ciphertext = ciphertext + message.charAt(i); i++; }

for(int i=1;i< message.length();i++)

{ ciphertext = ciphertext + message.charAt(i); i++; }

System.out.println("The ciphertext is :" + ciphertext); System.exit(0);

}

int distance,distance1; rounds=1; String[] ciphers = new String[key];

if(key != 2) { if(key%2==0)

{ distance = key+1; } else distance = key;

distance1 = distance;

for(int i=1; i<=message.length(); i++)

{ if((i+distance+1) <= message.length()) rounds++; i +=distance; }

if(key%2==0) { int j=0;

for(int i=0;i< rounds;i++)

{ ciphers[0] = ciphers[0] + message.charAt(j); j++;

for(int k=1; k < key-1;k++)

{

ciphers[k] = ciphers[k] + message.charAt(j); distance = distance - 2;

if((j+distance+1) < message.length())

ciphers[k] = ciphers[k] + message.charAt((j+distance+1)); j++;

}

if(j< message.length())ciphers[key-1] = ciphers[key-1] + message.charAt(j);

distance = distance1; j += distance/2 + 1; }

}else { System.out.println(rounds); int j=0;

for(int i=0;i< rounds;i++)

{ ciphers[0] = ciphers[0] + message.charAt(j); j++;

if(j<message.length())

{ for(int k=1; k < key-1;k++)

{ ciphers[k] = ciphers[k] + message.charAt(j); distance = distance - 2;

if((j+distance+1) < message.length())

ciphers[k] = ciphers[k] + message.charAt((j+distance+1)); j++; }

if(j< message.length())ciphers[key-1] = ciphers[key-1] + message.charAt(j);

distance = distance1; j += distance/2 + 1; } } }

}

for(String v : ciphers) s = s + (v.substring(4,(v.length())));

return s;

}

private String decryption()throws IOException

{ String ciphertext = ""; System.out.println("Please enter the ciphertext :");

b = new BufferedReader(new InputStreamReader(System.in));

ciphertext = b.readLine(); System.out.println("Please enter the key :");

int key = Integer.parseInt(b.readLine()); int distance,distance1;

if(key%2==0) { distance = key+1; }

else distance = key; distance1 = distance; char ptext[] = new char[ciphertext.length()];

for(int u=0;u< ciphertext.length();u++) ptext[u] = 'X';

int dist_of_lastround = rounds + distance1* (rounds-1);

boolean hasprimarybranch = false; boolean hassecbranch = false;

if((ciphertext.length() - dist_of_lastround) > 0) hasprimarybranch = true;

if((ciphertext.length() - dist_of_lastround) > (key-1)) hassecbranch = true;

int prim_count=0; int sec_count=0;

if(hasprimarybranch) prim_count = ciphertext.length() - dist_of_lastround;

if((ciphertext.length() - dist_of_lastround) == (key-1)) prim_count = prim_count - 1;

if(hassecbranch) sec_count = ciphertext.length() - (dist_of_lastround + (key-1));

int i=0;for(int j=0;j<rounds;j++)

{ ptext[i] = ciphertext.charAt(j); i += distance + 1; }i = rounds; int counter; String primary = "";

String secondary = ""; for(int k=1;k<key-1;k++)

{ counter = k; distance = distance - 2;

for(int l=0;l< rounds-1; l++)

{ ptext[counter] = ciphertext.charAt(i);

counter += (distance) + 1; i++; ptext[counter] = ciphertext.charAt(i);

counter = (l+1) + distance1*(l+1)+ k; i++; }

if(hasprimarybranch && prim_count >0)

{ primary = primary + ciphertext.charAt(i); i++; prim_count--; }

if(hassecbranch && sec_count > 1)

{ secondary = secondary + ciphertext.charAt(i); i++; sec_count--; }

}

counter = key-1; for(int l=0;l< rounds-1; l++)

{ ptext[counter] = ciphertext.charAt(i);

counter += distance1 + 1; i++; }

if(hasprimarybranch && (ciphertext.length()-dist_of_lastround == (key-1))) primary = primary + ciphertext.charAt(i);

String text = ""; for(char c : ptext) if(c != 'X') text = text + c;

text = text + primary;

return text;

}

public static void main(String[] args)throws IOException

{

railfence r = new railfence();

String ciphertext = r.encryption();

System.out.println("The ciphertext is : "+ciphertext);

String ptext = r.decryption();

System.out.println("The plaintext is : " + ptext);

}

}

OUTPUT :