public void Challenge12_Byte_at_a_time_ECB_decryption_simple()
{
var secretSuffix = Convert.FromBase64String(
"Um9sbGluJyBpbiBteSA1LjAKV2l0aCBteSByYWctdG9wIGRvd24gc28gbXkgaGFpciBjYW4gYmxvdwpUaGUgZ2lybGllcyBvbiBzdGFuZGJ5IHdhdmluZyBqdXN0IHRvIHNheSBoaQpEaWQgeW91IHN0b3A/IE5vLCBJIGp1c3QgZHJvdmUgYnkK");
using (var rnd = RandomNumberGenerator.Create())
{
var key = new byte[16];
rnd.GetBytes(key);
Func <ReadOnlyMemory <byte>, byte[]> encrypt = data => MyAes.EncryptEcb(data.Span, secretSuffix, key);
var blockSize = AesOracle.GuessBlockSize(encrypt);
Assert.Equal(16, blockSize);
var payload = new byte[3 * blockSize];
var encrypted = encrypt(payload);
Assert.Equal(CipherMode.ECB, AesOracle.GuessMode(encrypted, blockSize));
var calculatedPrefixLength = AesOracle.GetPrefixLength(blockSize, encrypt);
Assert.Equal(0, calculatedPrefixLength);
var decrypted = AesOracle.ByteAtATimeEcb(blockSize, encrypt);
var plainText = Encoding.UTF8.GetString(decrypted);
var secretText = Encoding.UTF8.GetString(secretSuffix);
Assert.Equal(secretText, plainText);
}
}
public void Challenge11_ECB_CBC_DetectionOracle()
{
int size = 16 * 3;
var payload = new byte[size];
for (int i = 0; i < 100; ++i)
{
var randomlyEncrypted = RandomEncryptor.Encrypt(payload);
Assert.Equal(0, randomlyEncrypted.cipher.Length % 16);
Assert.Equal(randomlyEncrypted.mode, AesOracle.GuessMode(randomlyEncrypted.cipher, 16));
}
}
