static byte[] function1(string inputString)
{
const string PREPEND_STRING = "comment1=cooking%20MCs;userdata=";
const string APPEND_STRING = ";comment2=%20like%20a%20pound%20of%20bacon";
byte[] key = new byte[] { 10, 11, 23, 44, 51, 23, 34,
89, 101, 65, 43, 71, 92, 41, 85, 03 };
byte[] IV = new byte[] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
//Construct the string
string unmodified = PREPEND_STRING + inputString + APPEND_STRING;
//Escape the required characters
string modified = unmodified.Replace(";", " ").Replace("=", " ");
//Convert to bytes
byte[] plainBytes = Encoding.ASCII.GetBytes(modified);
//Apply appropriate padding
byte[] paddedBytes = CryptoHelpers.Pkcs7PaddUp(plainBytes);
//Encrypt under CBC with key
byte[] encryptedBytes = CryptoHelpers.CbcEncrypt(paddedBytes, key, IV);
return(encryptedBytes);
}
static string challenge11()
{
//Create plaintext string and random key.
byte[] plainText = Encoding.ASCII.GetBytes(
"\"Nothing is particularly hard if you divide it into small jobs.\" — Henry Ford");
byte[] key = new byte[16];
Random random = new Random();
random.NextBytes(key);
//Create padding arrays and fill with random bytes
byte[] firstPad = new byte[random.Next(5, 10)];
random.NextBytes(firstPad);
byte[] secondPad = new byte[random.Next(5, 10)];
random.NextBytes(secondPad);
//Create an array to store randomized plain text,
//then combine data from existing arrays into plainBytes
byte[] plainBytes = new byte[firstPad.Length + plainText.Length + secondPad.Length];
Array.Copy(firstPad, 0, plainBytes, 0, firstPad.Length);
Array.Copy(plainText, 0, plainBytes, firstPad.Length, plainText.Length);
Array.Copy(secondPad, 0, plainBytes,
firstPad.Length + plainText.Length, secondPad.Length);
byte[] IVector = new byte[] { 00, 00, 00, 00, 00, 00, 00,
00, 00, 00, 00, 00, 00, 00, 00, 00 };
byte[] encrpyted = CryptoHelpers.Pkcs7PaddUp(plainBytes);
int whichEncrypyMethod = random.Next(2);
whichEncrypyMethod = 1;
//Attempt encryption functions.
if (whichEncrypyMethod == 0)
{
encrpyted = CryptoHelpers.CbcEncrypt(encrpyted, key, IVector);
Console.WriteLine("Encrypted with CBC decryption");
}
else if (whichEncrypyMethod == 1)
{
encrpyted = CryptoHelpers.EcbEncrypt(encrpyted, key);
Console.WriteLine("Encrypted with ECB decryption");
}
else
{
Console.WriteLine("Else statement hit, this is an issue");
}
Console.WriteLine("Encrypted: {0}", Encoding.Default.GetString(encrpyted));
//Attempt decryption.
byte[] decrypted = new byte[encrpyted.Length];
try
{
decrypted = CryptoHelpers.CbcDecrypt(encrpyted, key, IVector);
Console.WriteLine("Decrypted: {0}", Encoding.Default.GetString(decrypted));
Console.WriteLine("Decrypted with CBC decryption");
}
catch (Exception e)
{
Console.WriteLine(e);
try
{
decrypted = CryptoHelpers.EcbDecrypt(encrpyted, key);
Console.WriteLine("Decrypted: {0}", Encoding.Default.GetString(decrypted));
Console.WriteLine("Decrypted with ECB decryption");
}
catch (Exception E)
{
Console.WriteLine(E);
Console.WriteLine("Back to the drawing board.");
}
}
int test = CryptoHelpers.ECBorCBC(encrpyted, key);
Console.WriteLine(test);
return("");
}
