static string function2(byte[] data)
{
//Static values for decryption.
byte[] IV = new byte[] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
byte[] key = new byte[] { 10, 11, 23, 44, 51, 23, 34,
89, 101, 65, 43, 71, 92, 41, 85, 03 };
//Brute force each possible byte combination until we come up with a valid answer.
for (int a = 0; a < 255; a++)
{
int holder1 = a;
data[36] = (byte)holder1;
string holdByte = CryptoHelpers.Base64ToAscii(
CryptoHelpers.ByteArrayToBase64String(CryptoHelpers.CbcDecrypt(data, key, IV)));
if (holdByte.Contains(";admin"))
{
break;
}
}
for (int a = 0; a < 255; a++)
{
int holder2 = a;
data[42] = (byte)holder2;
string holdByte = CryptoHelpers.Base64ToAscii(
CryptoHelpers.ByteArrayToBase64String(CryptoHelpers.CbcDecrypt(data, key, IV)));
if (holdByte.Contains(";admin=true"))
{
break;
}
}
for (int a = 0; a < 255; a++)
{
int holder3 = a;
data[47] = (byte)holder3;
string holdByte = CryptoHelpers.Base64ToAscii(
CryptoHelpers.ByteArrayToBase64String(CryptoHelpers.CbcDecrypt(data, key, IV)));
if (holdByte.Contains(";admin=true;"))
{
break;
}
}
return(CryptoHelpers.Base64ToAscii(
CryptoHelpers.ByteArrayToBase64String(CryptoHelpers.CbcDecrypt(data, key, IV))));
}
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("");
}
