public static byte[] AESEncryptionOracle(byte[] input, out bool isECB)
{
var randomPrefixLength = random.Next(5, 11);
var randomPrefixBuffer = new byte[randomPrefixLength];
random.NextBytes(randomPrefixBuffer);
var randomSuffixLength = random.Next(5, 11);
var randomSuffixBuffer = new byte[randomSuffixLength];
random.NextBytes(randomSuffixBuffer);
var paddedInput = new byte[randomPrefixLength + input.Length + randomSuffixLength];
Array.Copy(randomPrefixBuffer, 0, paddedInput, 0, randomPrefixLength);
Array.Copy(input, 0, paddedInput, randomPrefixLength, input.Length);
Array.Copy(randomSuffixBuffer, 0, paddedInput, randomPrefixLength + input.Length, randomSuffixLength);
if (paddedInput.Length % 16 != 0)
{
paddedInput = BlockPad(paddedInput, paddedInput.Length + (16 - paddedInput.Length % 16));
}
isECB = random.Next(0, 2) == 1;
if (isECB)
{
return(AES128.EncryptECB(paddedInput, randomKey));
}
else
{
var iv = RandomAES128Key();
return(AES128.EncryptCBC(paddedInput, randomKey, iv));
}
}
public static byte[] CBCBitflipOracle(string payload)
{
var prefix = "comment1=cooking%20MCs;userdata=";
var suffix = ";comment2=%20like%20a%20pound%20of%20bacon";
//note that if you Escape all values you can't bitflip attack
//payload = Uri.EscapeDataString(payload)
payload = payload.Replace(";", "%3b").Replace("=", "%3d");
var newSource = string.Concat(prefix, payload, suffix);
var paddedSource = Pad16(Encoding.UTF8.GetBytes(newSource));
var iv = Encoding.UTF8.GetBytes("YELLOW SUBMARINE");
return(AES128.EncryptCBC(paddedSource, randomKey, iv));
}