/// <summary>
/// Decrypts assignment ciphertext.
/// </summary>
public static void ReadandDecryptAssignment()
{
String[] lines = { "fqjcb rwjwj vnjax bnkhj whxcq nawjv nfxdu mbvnu ujbbf nnc",
"oczmz vmzor jocdi bnojv dhvod igdaz admno ojbzo rcvot jprvi oviyv aozmo cvooj ziejt dojig toczrdnzno jahvi fdiyv xcdzq zoczn zxjiy",
"ejitp spawa qleji taiul rtwll rflrl laoat wsqqj atgac kthls iraoa twlpl qjatw jufrh lhuts qataq itats aittkstqfj cae",
"iyhqz ewqin azqej shayz niqbe aheum hnmnj jaqii yuexq ayqkn jbeuq iihed yzhni ifnun sayiz yudhesqshu qesqa iluym qkque aqaqm oejjs " +
"hqzyu jdzqa diesh niznj jayzy uiqhq vayzq shsnj jejjz nshnahnmyt isnae sqfun dqzew qiead zevqi zhnjq shqze udqai jrmtq uishq ifnun " +
"siiqa suoij qqfni syyle iszhnbhmei squih nimnx hsead shqmr udquq uaqeu iisqe jshnj oihyy snaxs hqihe lsilu ymhni tyz" };
Console.WriteLine("\nPlease be aware, this algorithm may take a couple tries to get the complete answer.");
Console.WriteLine("#4 doesn't fully solve due to old english, but it gets close enough.");
foreach (String s in lines)
{
String response = null;
do
{
Console.Write("\n\nCipher Text: {0}\nDeciphering....Please Wait.\n", s);
Dictionary <char, char> key = SubstitutionDecipher.Decipher(s.Replace(" ", String.Empty));
String strKey = "";
String strCipher = "";
foreach (KeyValuePair <char, char> kvp in key)
{
strCipher += kvp.Key;
strKey += kvp.Value;
}
Console.WriteLine("Cipher letters: " + strCipher);
Console.WriteLine("Key : " + strKey);
Console.WriteLine("Deciphered text: " + SubstitutionDecipher.DecipherMessageUsingKey(key, s.Replace(" ", String.Empty)));
Console.Write("Is that correct? (Y/N): ");
response = Console.ReadLine().ToLower();
} while (response.Equals("n"));
}
}
/// <summary>
/// Prompts user for ciphertext and corresponding key, and decrypts the ciphertext.
/// </summary>
/// <returns>Returns a string corresponding to the deciphered plain text.</returns>
public static String DecryptUserCipher()
{
Dictionary <char, char> key = new Dictionary <char, char>();
bool issue = false;
//get ciphertext
Console.Write("Please enter the ciphertext:");
String cipherText = Console.ReadLine();
//remove any punctuation, symbols, or spaces
cipherText = new String(cipherText.Where(c => char.IsLetter(c)).ToArray()).ToLower();
do
{
Console.Write("\nPlease enter the key as a string like \"abcdefghijklmnopqrstuvwxyz\", where the first letter corresponds to the letter 'a' in the ciphertext, the second to 'b'.... the last to 'z'\n");
Console.Write("Key: ");
String userKey = Console.ReadLine();
userKey = new String(userKey.Where(c => char.IsLetter(c)).ToArray()).ToLower();
//check if key is long enough, we want a full 26 letter key
if (userKey.Length < 26 || userKey.Length > 26)
{
Console.WriteLine("Key too short or long; current length: " + userKey.Length);
issue = true;
}
else
{
//build key
issue = false;
int pos = 0;
String alphabet = "abcdefghijklmnopqrstuvwxyz";
foreach (char c in userKey)
{
key.Add(c, alphabet[pos++]);
}
}
} while (issue);
return(SubstitutionDecipher.DecipherMessageUsingKey(key, cipherText));
}
