import java.util.Scanner; public class Program { public static void main(String[] args) { // Hello Everyone this is a simple Cryptography // using vegenère cipher where you match every // word with a key and pick a corresponding letter // to the word. // For example Using the word "Sololearn" and // the word "Web" as our key, the following will // Be done to encrypt the text: // w + s = o // e + o = s // b + l = m // w + o = k // e + l = p // b + e = f // w + a = w // e + r = v // b + n = o // Resulting word = "osmkpfwvo" //THE TABLE IN THIS CODE WILL HELP GUIDE YOU /** - Enter two words in two lines: * - The first line should be the message you * want to encrypt. * - The second is the key you want to use * - Avoid using Symbols and digits on the * key*/ System.out.println("**VEGENÈRE CIPHER**\n"); System.out.println("PLEASE USE LANDSCAPE " + " MODE TO VIEW THE TABLE PROPERLY"); Scanner input = new Scanner(System.in); String w = ""; String k = ""; int j = 0; try{ w = input.nextLine(); if(w.equals("")) throw new Exception("EmptyValueException"); } catch(Exception e){ System.out.println("\nDetected wrong " + "input.\nUsing defaults:"); w = "Hello World! Learn Cryptography" + " on Sololearn."; } try{ k = input.nextLine().replaceAll( "[\\d+\\s+\\W+]",""); }catch(Exception exception){ for(int i=0; i<15; i++){ j =(int)Math.round(Math.random()*26); k+= "abcdefghijklmnopqrstuvwxyz". charAt(j) + ""; } System.out.println("\nNo Key Detected." + "\nUsing Random Key:"); } if(k.length() == 0){ System.out.println("\nUsing Random Key"); for(int i=0; i<15; i++){ j =(int)Math.round(Math.random()*26); k+= "abcdefghijklmnopqrstuvwxyz". charAt(j) + ""; } } // E N C R Y P T I O N T A B L E System.out.println("\nENCRYPTION TABLE:-"); int e = 0; for(char c = 'A' - 1; c <= 'Z'; c++){ if(c > 'A' - 1){ System.out.print( ((c == 'M')? "KEY: |": " |") + c + "| "); }else System.out.print(" "); for(char d = c; d <= 'Z'; d++){ ++e; if(c == 'A' - 1){ System.out.print(((d == 'I')? "WORD LETTER:": " "));} else System.out.print(d + " "); if(d == 'Z'){ d = 'A' - 1; } if( e == 26) break; } e = 0; System.out.print("\n"); } System.out.println("\nWord entered: \t" + w); System.out.println("Key used: \t\t\t" + k); // E N C Y P T I N G String enMsg = encrypt(k, w); // E N C R Y P T E D System.out.println(); System.out.println ("\nD E C R Y P T I N G...\n"); // D E C R E P T I N G decrypt(k, enMsg); } //Additional methods static int position(char c){ int pos = 0; for(char i = 'a'; i <= 'z' + 1; i++){ ++pos; if( i == Character.toLowerCase(c) ) break; } return (pos == 27)? -1: pos; } static String letter(int p){ String[] letters = "abcdefghijklmnopqrstuvwxyz".split(""); return letters[p]; } static String encrypt(String k, String w) { int j = 1; int p = 0; char n = 'a'; String output = ""; int z = 0; String newKey = ""; char ch = 'a'; System.out.println("\nPROCESS OF " + "ENCRYPTING:"); System.out.println("\t\t\tKEY\t\tWORD\t\t\t" + "ENCRYPTION"); for(int i = 0; i < w.length(); i++){ ch = w.charAt(i); if(!Character.toString(ch).matches ("[A-Za-z]")){ newKey += k.charAt((--z < 0)? 0: z);} else newKey += k.charAt(z); if(z == k.length() - 1) z = -1; z++; } for(int m = 0; m < w.length(); m++){ if(Character.toString(w.charAt(m)).matches ("[A-Za-z]")){ p = position(w.charAt(m)); n = newKey.charAt(m); }else{ output += w.charAt(m); continue; } for(; n <= 'z'; n++){ if( p == j){ output += letter(position(n) -1); break; } ++j; n = (n == 'z')? 'a' - 1: n; } j = 1; System.out.println("\t\t\t" + Character.toUpperCase(newKey.charAt(m)) + "\t\t+\t\t" + Character.toUpperCase(w.charAt(m)) + "\t\t\t=\t\t" + letter(position(n) -1).toUpperCase()); } System.out.print("\nCipher text: \t"+ output); return output; } static void decrypt(String k, String w){ System.out.println("\nPROCESS OF " + "DECRYPTING:"); System.out.println("\t\t\tKEY\t\tENCR.\t\t" + "DECRYPTION"); int z = 0; String newKey = ""; char ch = 'a'; for(int i = 0; i < w.length(); i++){ ch = w.charAt(i); if(!Character.toString(ch).matches ("[A-Za-z]")){ newKey += k.charAt((--z < 0)? 0: z);} else newKey += k.charAt(z); if(z == k.length() - 1) z = -1; z++; } k = newKey; String output = ""; int j = 1; for(int i = 0; i < k.length(); i++){ ch = w.charAt(i); if(!Character.toString(ch).matches ("[A-Za-z]")){ output += w.charAt(i); continue; } for(char c = k.charAt(i); c <= 'z'; c++){ if(c == ch){ output += letter(j - 1); ch = c; break; } ++j; c = (c == 'z')? 'a' -1: c; } System.out.println("\t\t\t" + Character.toUpperCase(newKey.charAt(i)) + "\t\t-\t\t" + Character.toUpperCase(w.charAt(i)) + "\t\t\t=\t\t" + letter(j - 1).toUpperCase()); j = 1; } System.out.print("\nPlain text: \t" +output); } }

Vegenère Cipher