internal void _Decrypt(Stream inputStream, Stream outputStream, byte[] password)
{
var info = new byte[HashLengthSize + SaltLengthSize + EncryptedLengthSize];
inputStream.Read(info, 0, info.Length);
var hashLength = BitConverter.ToInt32(info, 0);
var saltLength = BitConverter.ToInt32(info, HashLengthSize);
var encryptedLength = BitConverter.ToInt64(info, HashLengthSize + SaltLengthSize);
byte[] salt = new byte[saltLength], hash = new byte[hashLength];
inputStream.Read(hash,0, hashLength);
inputStream.Read(salt, 0, saltLength);
using (var rfc2898 = new Rfc2898DeriveBytes(password, salt, DefaultIteration))
using (var algorithm = GetSymmetricAlgorithm())
{
algorithm.KeySize = DefaultKeySize;
algorithm.BlockSize = DefaultBlockSize;
var key = rfc2898.GetBytes(DefaultKeySize / 8);
var iv = rfc2898.GetBytes(DefaultBlockSize / 8);
using (var transform = algorithm.CreateDecryptor(key, iv))
using (var hasher = IncrementalHash.CreateHMAC(DefaultHashAlgorithm, password))
using (var crytoStream = new CryptoStream(outputStream, transform, CryptoStreamMode.Write))
{
foreach (var bytes in inputStream.ReadByChunk(Config.DefaultChunkSize, encryptedLength))
{
hasher.AppendData(bytes);
crytoStream.Write(bytes, 0, bytes.Length);
}
if (!hash.SequenceEqual(hasher.GetHashAndReset()))
throw new Exception("HMAC value is not correct");
}
}
}
internal void _EncryptThenMac(Stream inputStream, Stream outputStream, byte[] password, byte[] salt)
{
using (var rfc2898 = new Rfc2898DeriveBytes(password, salt, DefaultIteration))
using (var algorithm = GetSymmetricAlgorithm())
{
algorithm.KeySize = DefaultKeySize;
algorithm.BlockSize = DefaultBlockSize;
var key = rfc2898.GetBytes(DefaultKeySize / 8);
var iv = rfc2898.GetBytes(DefaultBlockSize / 8);
long encryptedLength = 0;
using (var transform = algorithm.CreateEncryptor(key, iv))
using (var hasher = IncrementalHash.CreateHMAC(DefaultHashAlgorithm, password))
using (var delegateStream = new DelegateStream(outputStream, null, (buffer, offset, count) => { encryptedLength += buffer.Length; hasher.AppendData(buffer); }))
{
var hash = hasher.GetHashAndReset();
outputStream.Write(BitConverter.GetBytes(hash.Length), 0, HashLengthSize);
outputStream.Write(BitConverter.GetBytes(salt.Length), 0, SaltLengthSize);
outputStream.Write(BitConverter.GetBytes(encryptedLength), 0, EncryptedLengthSize);
outputStream.Write(hash, 0, hash.Length);
outputStream.Write(salt, 0, salt.Length);
using (var crytoStream = new CryptoStream(delegateStream, transform, CryptoStreamMode.Write))
{
foreach (var bytes in inputStream.ReadByChunk())
crytoStream.Write(bytes, 0, bytes.Length);
}
outputStream.Seek(HashLengthSize + SaltLengthSize, SeekOrigin.Begin);
outputStream.Write(BitConverter.GetBytes(encryptedLength), 0, EncryptedLengthSize);
outputStream.Write(hasher.GetHashAndReset(), 0, hash.Length);
}
}
}