I am doing a Caesar's cipher assignment where you have to encrypt and decrypt a word with a +5 letter key. I am struggling making the Decrypt function work as I get an exception that the index is out of range. I know that there is something wrong with what is getting passed into the function as it does not seem to register the previous moves of the encryptor so when I try to decrypt it through the letterPosition - 5 to revert it back from the letterPosition + 5 it does not seem to understand and puts the index out of range. Thanks
{
public class Cipher
{
public Cipher(){}
char[] encryptedMessage;
string encodedString;
string input;
public void method()
{
char[] alphabet = new char[] {'a','b','c','d','e','f','g'
,'h','i','j','k','l','m','n','o','p','q','r','s','t','u'
,'v','w','x','y','z'};
Console.WriteLine("Enter you secret phrase");
input = Console.ReadLine();
char[] secretMessage = input.ToCharArray();
char[] encryptedMessage = new char[secretMessage.Length];
for (int i = 0; i < secretMessage.Length; i++)
{
char letter = secretMessage[i];
int letterPosition = Array.IndexOf(alphabet, letter);
int newLetterPosition = (letterPosition + 5) % 26;
char letterEncoded = alphabet[newLetterPosition];
encryptedMessage[i] = letterEncoded;
}
encodedString = String.Join(" ", encryptedMessage);
Console.WriteLine($"Your encoded message is {encodedString}");
Console.WriteLine($"The decoded message is {input}");
}
public void Decrypt()
{
for (int i = 0; i < secretMessage.Length; i++)
{
char letter = secretMessage[i];
int letterPosition = Array.IndexOf(alphabet, letter);
int newLetterPosition = (letterPosition - 5) % 26;
char letterEncoded = alphabet[newLetterPosition];
encryptedMessage[i] = letterEncoded;
}
encodedString = String.Join(" ", encryptedMessage);
Console.WriteLine($"Your encoded message is {encodedString}");
Console.WriteLine($"The decoded message is {input}");
}
}
}
