public static void main(String[] args) throws IOException {
// reads in text file
Scanner file = new Scanner(new FileReader("input.txt"));
String message = file.useDelimiter("\\A").next();
// capitalizes all letters and gets rid of blank spaces
message = message.toUpperCase();
message = message.replaceAll("\\s+", "");
int cipher, encrypt_decrypt;
// asks user of they want to encrypt or decrypt a message
System.out.println("Do you want to encrypt or decrypt?");
System.out.println("1 - Encrypt a message");
System.out.println("2 - Decrypt a message");
encrypt_decrypt = cin.nextInt();
// asks user which algorithm to use
System.out.println("Which cipher do you want to use?");
System.out.println("1 - Shift Cipher");
System.out.println("2 - Affine Cipher");
System.out.println("3 - Substitution Cipher");
System.out.println("4 - Vigenere Cipher");
cipher = cin.nextInt();
ciphers(message, cipher, encrypt_decrypt);
}
public static void ciphers(String message, int cipher, int encrypt_decrypt) {
// determines which function to use depending on user input
if (cipher == 1) {
// asks user for a key
System.out.println("Enter a key value: ");
int k = cin.nextInt();
if (encrypt_decrypt == 1) {
shift(message, k);
} else {
shift(message, -k);
}
} else if (cipher == 2) {
// asks user for a key
System.out.println("Enter a key value: ");
int k = cin.nextInt();
// asks user for 'b' value
System.out.println("Enter a 'b' value: ");
int b = cin.nextInt();
if (encrypt_decrypt == 1) {
affine(message, k, b, 1);
} else {
affine(message, k, b, 2);
}
} else if (cipher == 3) {
// asks user for a keyword & gets rid of repeated characters
System.out.println("Enter a keyword: ");
String keyword = cin.next();
keyword = keyword.toUpperCase();
keyword =
keyword.replaceAll(
(String.format("(.)(?<=(?:(?=\\1).).{0,%d}(?:(?=\\1).))", keyword.length())), "");
if (encrypt_decrypt == 1) {
substitution(message, keyword, 1);
} else {
substitution(message, keyword, 2);
}
} else if (cipher == 4) {
// asks user for a keyword
System.out.println("Enter a keyword: ");
String keyword = cin.next();
keyword = keyword.toUpperCase();
if (encrypt_decrypt == 1) {
vigenere(message, keyword, 1);
} else {
vigenere(message, keyword, 2);
}
}
}