Java code for Vigenere Cipher - study materials for competitive exams

The encryption code inputs a line of characters as plaintext as well as a key String and encrypts the line using the key String based on Vigenere Cipher. The output is printed to the terminal. The decryption code inputs a line of characters as ciphertext as well as a key String and decrypts the line using the key String based on Vigenere Cipher. The plaintext is printed to the terminal. Note that Vigenere Cipher is a symmetric key algorithm.

Encryption Code :-

import java.io.*;
import java.util.Scanner;
class vigenereCipherEn{
public static void main(String[] args){
int tableRowSize = 93;
int tableColumnSize = 93;
int vignereTable[][] = new int[93][93];
Scanner input = new Scanner(System.in);
for (int rows = 0; rows < tableRowSize; rows++){
for (int columns = 0; columns < tableColumnSize; columns++){
vignereTable[rows][columns] = (rows + columns) % 93;
}
}
System.out.println("Enter the plaintext");
String plainText = input.nextLine();
System.out.print("Enter the key: ");
String key = input.nextLine();
String cipherText = "";
int keyIndex = 0;
for (int ptextIndex = 0; ptextIndex < plainText.length();
ptextIndex++){
char pChar = plainText.charAt(ptextIndex);
int asciiVal = (int) pChar; if (pChar == ' '){
cipherText += pChar;
continue;
}
if (asciiVal < 30 || asciiVal > 123){
cipherText += pChar;
continue;
}

int basicPlainTextValue = ((int) pChar) - 31;

char kChar = key.charAt(keyIndex);
int basicKeyValue = ((int) kChar ) - 31;
int tableEntry = vignereTable[basicPlainTextValue][basicKeyValue];
char cChar = (char) (tableEntry + 31);
cipherText += cChar;
keyIndex++;
if (keyIndex == key.length())
keyIndex = 0;

}
System.out.println(" cipher text is "+cipherText);
}
}
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Decryption Code :-

import java.io.*;
import java.util.Scanner;
class vigenereCipherDe{
public static void main(String[] args){
int tableRowSize = 93;
int tableColumnSize = 93;
int vignereTable[][] = new int[93][93];
Scanner input = new Scanner(System.in);
for (int rows = 0; rows < tableRowSize; rows++){
for (int columns = 0; columns < tableColumnSize; columns++){
vignereTable[rows][columns] = (rows + columns) % 93;
}
}
System.out.println("Enter the cipher text");
String cipherText = input.nextLine();
System.out.print("Enter the key: ");
String key = input.nextLine();
String plainText = "";
int keyIndex = 0;
for (int ctextIndex = 0; ctextIndex < cipherText.length();
ctextIndex++){
char cChar = cipherText.charAt(ctextIndex);
int asciiVal = (int) cChar;
if (cChar == ' '){
plainText += cChar;
continue;
}
if (asciiVal < 30 || asciiVal > 123){
plainText += cChar;
continue;
}
    int basiccipherTextValue = ((int) cChar) - 31;
char kChar = key.charAt(keyIndex);
int basicKeyValue = ((int) kChar ) - 31;
    for (int pIndex = 0; pIndex < tableColumnSize; pIndex++){
if (vignereTable[basicKeyValue][pIndex] == basiccipherTextValue){
char potcChar = (char)
(vignereTable[basicKeyValue][pIndex] + 31);
char potpChar = (char) (pIndex + 31);
plainText += potpChar;
}
}
keyIndex++;
if (keyIndex == key.length())
   keyIndex = 0;
}
System.out.println(" plain text is "+plainText);
}
}