public DataInstance decryptData(DataInstance dataInst)
{
int index = dataInst.encryptRounds.Count - 1;
while (index >= 0 && checkIfCanDecrypt(dataInst.encryptRounds[index]))
{
EncryptRound round = dataInst.encryptRounds[index];
byte[] decryptedKey = RSAProvider.Decrypt(round.key, USE_AOEP);
byte[] plain;
int count;
using (MemoryStream mStream = new MemoryStream(dataInst.data))
{
using (AesCryptoServiceProvider aesProvider = new AesCryptoServiceProvider())
{
using (CryptoStream cryptoStream = new CryptoStream(mStream,
aesProvider.CreateDecryptor(decryptedKey, round.IV), CryptoStreamMode.Read))
{
plain = new byte[dataInst.data.Length];
count = cryptoStream.Read(plain, 0, plain.Length);
}
}
}
dataInst.data = new byte[count];
Array.Copy(plain, dataInst.data, count);
dataInst.encryptRounds.RemoveAt(index);
index--;
}
return(dataInst);
}
public DataInstance?chunkToInstance(DataChunk chunk)
{
byte[] hash = HashProvider.ComputeHash(chunk.data);
EncryptRound lastRound = chunk.encryptRounds.Last();
if (
!lastRound.hash.SequenceEqual(hash) ||
!RSAProvider.VerifyHash(hash, HASH_ALGORITHM_NAME, lastRound.sign))
{
return(null);
}
return(new DataInstance(chunk.data, chunk.hashOrigin, chunk.signOrigin, chunk.encryptRounds));
}
public DataInstance encryptData(DataInstance dataInst, int roundsCount = 1)
{
DataInstance instance = dataInst;
instance.encryptRounds = new List <EncryptRound>(dataInst.encryptRounds);
for (int i = 0; i < roundsCount; i++)
{
AESProvider.GenerateKey();
AESProvider.GenerateIV();
byte[] key = AESProvider.Key;
byte[] IV = AESProvider.IV;
//let's encrypt data
byte[] encrypted;
using (MemoryStream mstream = new MemoryStream())
using (AesCryptoServiceProvider aesProvider = new AesCryptoServiceProvider())
{
using (CryptoStream cryptoStream = new CryptoStream(mstream,
aesProvider.CreateEncryptor(key, IV), CryptoStreamMode.Write))
cryptoStream.Write(instance.data, 0, instance.data.Length);
encrypted = mstream.ToArray();
}
instance.data = encrypted;
//now encrypt AES key
byte[] enKey = RSAProvider.Encrypt(key, USE_AOEP);
//and hash&sign
byte[] hash = HashProvider.ComputeHash(instance.data);
byte[] sign = RSAProvider.SignHash(hash, HASH_ALGORITHM_NAME);
//now create Encrypt Round
EncryptRound round = new EncryptRound(enKey, IV, hash, sign, instance.encryptRounds.Count);
//and add to rounds list
instance.encryptRounds.Add(round);
}
return(instance);
}
private bool checkIfCanDecrypt(EncryptRound round)
{
return(RSAProvider.VerifyHash(round.hash, HASH_ALGORITHM_NAME, round.sign));
}