Affine Cipher Code in java that also encrypts integer - validation

Question

private static int firstKey = 5;
private static int secondKey = 19;
private static int module = 26;
public static void main(String[] args) {
String input = "abcdefghijklmnopqrstuvwxyz";
String cipher = encrypt(input);
String deciphered = decrypt(cipher);
System.out.println("Source: " + input);
System.out.println("Encrypted: " + cipher);
System.out.println("Decrypted: " + deciphered);
}
static String encrypt(String input) {
StringBuilder builder = new StringBuilder();
for (int in = 0; in < input.length(); in++) {
char character = input.charAt(in);
// if (Character.isLetter(character)) {
character = (char) ((firstKey * (character - 'a') + secondKey) % module + 'a');
//}
builder.append(character);
}
return builder.toString();
}
static String decrypt(String input) {
StringBuilder builder = new StringBuilder();
// compute firstKey^-1 aka "modular inverse"
BigInteger inverse = BigInteger.valueOf(firstKey).modInverse(BigInteger.valueOf(module));
// perform actual decryption
for (int in = 0; in < input.length(); in++) {
char character = input.charAt(in);
// if (Character.isLetter(character)) {
int decoded = inverse.intValue() * (character - 'a' - secondKey + module);
character = (char) (decoded % module + 'a');
//}
builder.append(character);
}
return builder.toString();
}
i got this code from this site itself
but the above code does not decrpyt the integers ..
please help
above is a code that i got from this site.
but this doesnot decrypts the integer.
please help.

Answer 1

I have added two more functiond that incrypt and decrypt integers that work.You can use them when you want to incrypt, decrypt integers, and the previous functions when you want to enc/dec lower case alphabets
//Code
import java.math.BigInteger;
public class main{
private static int firstKey = 5;
private static int secondKey = 19;
private static int module = 26;
public static void main(String[] args) {
String input = "abcdefghijklmnopqrstuvwxyz";
String cipher = encrypt(input);
String deciphered = decrypt(cipher);
System.out.println("Source: " + input);
System.out.println("Encrypted: " + cipher);
System.out.println("Decrypted: " + deciphered);
System.out.println("\n");
//for Integer
String input1 = "826429837598327598327549832";
String cipher1 = encryptInt(input1);
String deciphered1 = decryptInt(cipher1);
System.out.println("Source: " + input1);
System.out.println("Encrypted: " + cipher1);
System.out.println("Decrypted: " + deciphered1);
}
static String encrypt(String input) {
StringBuilder builder = new StringBuilder();
for (int in = 0; in < input.length(); in++) {
char character = input.charAt(in);
// if (Character.isLetter(character)) {
character = (char) ((firstKey * (character - 'a') + secondKey) % module + 'a');
//}
builder.append(character);
}
return builder.toString();
}
static String decrypt(String input) {
StringBuilder builder = new StringBuilder();
// compute firstKey^-1 aka "modular inverse"
BigInteger inverse = BigInteger.valueOf(firstKey).modInverse(BigInteger.valueOf(module));
// perform actual decryption
for (int in = 0; in < input.length(); in++) {
char character = input.charAt(in);
// if (Character.isLetter(character)) {
int decoded = inverse.intValue() * (character - 'a' - secondKey + module);
character = (char) (decoded % module + 'a');
//}
builder.append(character);
}
return builder.toString();
}
//ENCRIPTION DECRIPTION FOR INTEGERS
static String encryptInt(String input) {
StringBuilder builder = new StringBuilder();
for (int in = 0; in < input.length(); in++) {
char character = input.charAt(in);
// if (Character.isLetter(character)) {
character = (char) ((firstKey * (character - '0') + secondKey) % module + '0');
//}
builder.append(character);
}
return builder.toString();
}
static String decryptInt(String input) {
StringBuilder builder = new StringBuilder();
// compute firstKey^-1 aka "modular inverse"
BigInteger inverse = BigInteger.valueOf(firstKey).modInverse(BigInteger.valueOf(module));
// perform actual decryption
for (int in = 0; in < input.length(); in++) {
char character = input.charAt(in);
// if (Character.isLetter(character)) {
int decoded = inverse.intValue() * (character - '0' - secondKey + module);
character = (char) (decoded % module + '0');
//}
builder.append(character);
}
return builder.toString();
}
}