public Message(Stream input, RSAPrivateKey key, Converter <Guid, Salt> sessionSecret)
{
(_protected = new MemoryStream(0)).Dispose();
_hash = new HashStream(new SHA256Managed(), input);
_payload = input;
ReadHeader(_hash, out _version, out _state, out _transferId, out _salt);
Salt secret;
if (!UsesSessionKey)
{
// Begin private key decryption
_payload = key.Decrypt(input);
_hash.ChangeStream(_payload);
// Decrypt the aes key used in this package
byte[] keybits = IOStream.Read(_hash, 32);
secret = Salt.FromBytes(keybits);
}
else
{
secret = sessionSecret(_transferId);
Check.IsEqual(32, Check.NotNull(secret).Length);
}
AESCryptoKey sessionKey = new AESCryptoKey(
// Prefix the key with the message's salt and compute a SHA256 hash to be used as the key
Hash.SHA256(_salt.GetData(secret.ToArray()).ToStream()).ToArray(),
// Compute an IV for this aes key and salt combination
IV(secret, _salt)
);
_payload = sessionKey.Decrypt(_payload);
_hash.ChangeStream(_payload);
}
//private bool _verified; /* this is a debugging aid used to ensure all messages are signed or verified */
public Message(TransferState state, Guid transferId, RSAPublicKey key, Converter <Guid, Salt> sessionSecret)
{
_version = VersionHeader;
_state = state;
_transferId = transferId;
_salt = new Salt(Salt.Size.b256);
_protected = new MemoryStream();
_payload = new NonClosingStream(_protected);
_hash = new HashStream(new SHA256Managed());
WriteHeader(_hash);
Salt secret;
if (!UsesSessionKey)
{
// Outer encryption is straight PKI based on the remote public key
_payload = key.Encrypt(_payload);
_hash.ChangeStream(_payload);
// Preceed the message with a new, AES key
secret = new Salt(Salt.Size.b256);
_hash.Write(secret.ToArray(), 0, 32);
}
else
{
secret = sessionSecret(_transferId);
Check.IsEqual(32, Check.NotNull(secret).Length);
}
AESCryptoKey sessionKey = new AESCryptoKey(
// Prefix the key with the message's salt and compute a SHA256 hash to be used as the key
Hash.SHA256(_salt.GetData(secret.ToArray()).ToStream()).ToArray(),
// Compute an IV for this aes key and salt combination
IV(secret, _salt)
);
_payload = sessionKey.Encrypt(_payload);
_hash.ChangeStream(_payload);
}