private void ComputeSignatureValues(AKEKeys ake_keys, byte[] x_byte_array_data, UInt64 aes_counter, bool is_top_half_keys)
{
if (ake_keys == null)
throw new ArgumentException("ComputeSignatureValues: AKE keys object should not be null");
if (is_top_half_keys == true && (ake_keys.GetAESKey1() == null || ake_keys.GetAESKey1().Length < 1))
throw new ArgumentException("ComputeSignatureValues: The AKE AES key 1 should not be null/empty");
if (is_top_half_keys == false && (ake_keys.GetAESKey2() == null || ake_keys.GetAESKey2().Length < 1))
throw new ArgumentException("ComputeSignatureValues: The AKE AES key 2 should not be null/empty");
if (x_byte_array_data == null || x_byte_array_data.Length < 1)
throw new ArgumentException("ComputeSignatureValues: The x_byte_array_data cannot be null/empty");
if (aes_counter < 0)
throw new ArgumentException("ComputeSignatureValues: The aes counter value cannot be less than zero");
byte[] _encrypted_signature_byte_array = null;
if (is_top_half_keys == true)
_encrypted_signature_byte_array = Utility.AESGetEncrypt(ake_keys.GetAESKey1(), x_byte_array_data, aes_counter);
else
_encrypted_signature_byte_array = Utility.AESGetEncrypt(ake_keys.GetAESKey2(), x_byte_array_data, aes_counter);
try
{
Utility.EncodeOTRDataBE(_encrypted_signature_byte_array, ref _encoded_encrypted_signature_byte_array);
}
catch (Exception ex)
{
throw new InvalidDataException("ComputeSignatureValues:" + ex.ToString());
}
if (is_top_half_keys == true && (ake_keys.GetMACKey2() == null || ake_keys.GetMACKey2().Length < 1))
throw new InvalidDataException("ComputeSignatureValues: The AKE MAC key 2 should not be null/empty");
if (is_top_half_keys == false && (ake_keys.GetMACKey4() == null || ake_keys.GetMACKey4().Length < 1))
throw new InvalidDataException("ComputeSignatureValues: The AKE MAC key 4 should not be null/empty");
if (is_top_half_keys == true)
_hashed_encoded_encrypted_byte_array = Utility.SHA256GetKeyedHash(ake_keys.GetMACKey2(), _encoded_encrypted_signature_byte_array);
else
_hashed_encoded_encrypted_byte_array = Utility.SHA256GetKeyedHash(ake_keys.GetMACKey4(), _encoded_encrypted_signature_byte_array);
_truncated_hash_signature = new byte[OTRConstants.MAC_SIGNATURE_LENGTH_BITS / 8];
Buffer.BlockCopy(_hashed_encoded_encrypted_byte_array, 0, _truncated_hash_signature, 0, _truncated_hash_signature.Length);
}
private static bool IsEncryptedSignatureVerified(AKEKeys ake_keys, DHKeyPair key_pair, byte[] their_public_key_mpi_byte_array,
byte[] encryted_byte_array, UInt64 counter, bool is_top_half_keys,ref UInt32 public_key_id, ref byte[] dsa_public_key_byte_array_encoded)
{
int _next_start_index = -1;
bool _is_verified = false;
byte[] _decrypted_x_data_array = null;
byte[] _hashed_m_data_signature = null;
byte[] _dh_kid_bytes = null;
byte[] _temp_byte_array = null;
byte[] _dsa_public_key_type = null;
byte[] _dsa_public_key_param_p_mpi = null;
byte[] _dsa_public_key_param_q_mpi = null;
byte[] _dsa_public_key_param_g_mpi = null;
byte[] _dsa_public_key_param_y_mpi = null;
try
{
/*get encrypted signature bytes*/
_next_start_index = 0;
_temp_byte_array = null;
_next_start_index = Utility.DecodeDataFromBytesBE(encryted_byte_array, _next_start_index, ref _temp_byte_array);
if (_temp_byte_array == null || _temp_byte_array.Length < 1)
throw new InvalidDataException("IsEncryptedSignatureVerified: The decoded Encrypted OTR Data type byte array cannot be null/empty");
if (is_top_half_keys == true)
_decrypted_x_data_array = Utility.AESGetDecrypt(ake_keys.GetAESKey1(), _temp_byte_array, counter);
else
_decrypted_x_data_array = Utility.AESGetDecrypt(ake_keys.GetAESKey2(), _temp_byte_array, counter);
if (_decrypted_x_data_array == null || _decrypted_x_data_array.Length < 1)
throw new InvalidDataException("IsEncryptedSignatureVerified: The decrypted byte array cannot be null/empty");
/*get public key parameter bytes*/
_next_start_index = 0;
_temp_byte_array = null;
//get public key type
int _pub_key_start_index = _next_start_index;
_next_start_index = Utility.DecodeShortFromBytes(_decrypted_x_data_array, _next_start_index, ref _dsa_public_key_type);
if (_dsa_public_key_type == null || _dsa_public_key_type.Length < 1)
throw new InvalidDataException("IsEncryptedSignatureVerified: The decoded DSA public key type byte array cannot be null/empty");
if (BitConverter.ToUInt16(_dsa_public_key_type,0) != OTRConstants.DSA_PUB_KEY_TYPE)
throw new InvalidDataException("IsEncryptedSignatureVerified: The DSA public key type is invalid");
//get MPI encoded DSA public key parameters
_next_start_index = Utility.DecoupleMpiFromBytes(_decrypted_x_data_array, _next_start_index, ref _dsa_public_key_param_p_mpi);
_next_start_index = Utility.DecoupleMpiFromBytes(_decrypted_x_data_array, _next_start_index, ref _dsa_public_key_param_q_mpi);
_next_start_index = Utility.DecoupleMpiFromBytes(_decrypted_x_data_array, _next_start_index, ref _dsa_public_key_param_g_mpi);
_next_start_index = Utility.DecoupleMpiFromBytes(_decrypted_x_data_array, _next_start_index, ref _dsa_public_key_param_y_mpi);
int _pub_key_end_index = _next_start_index;
//get the whole encoded DSA key
dsa_public_key_byte_array_encoded = new byte[_pub_key_end_index - _pub_key_start_index];
Buffer.BlockCopy(_decrypted_x_data_array, _pub_key_start_index, dsa_public_key_byte_array_encoded, 0, dsa_public_key_byte_array_encoded.Length);
DsaPublicKeyParameters _dsa_public_key_params = GetDSAPublicKeyParams(_dsa_public_key_param_p_mpi, _dsa_public_key_param_q_mpi, _dsa_public_key_param_g_mpi, _dsa_public_key_param_y_mpi);
/*Get DH Key ID bytes*/
_next_start_index = Utility.DecodeIntFromBytes(_decrypted_x_data_array, _next_start_index, ref _dh_kid_bytes);
if (_dh_kid_bytes == null || _dh_kid_bytes.Length < 1)
throw new InvalidDataException("IsEncryptedSignatureVerified: The decoded Key ID OTR Int type byte array cannot be null/empty");
public_key_id = BitConverter.ToUInt32(_dh_kid_bytes, 0);
/*Get Signed M_b*/
_hashed_m_data_signature = new byte[_decrypted_x_data_array.Length - _next_start_index];
Buffer.BlockCopy(_decrypted_x_data_array, _next_start_index, _hashed_m_data_signature, 0, _hashed_m_data_signature.Length);
if (_hashed_m_data_signature == null || _hashed_m_data_signature.Length < 1)
throw new InvalidDataException("IsEncryptedSignatureVerified: The extracted Signed byte array, M_b, cannot be null/empty");
/*Decode r and s */
_next_start_index = 0;
byte[] _decoded_signature_r_byte_array = null;
byte[] _decoded_signature_s_byte_array = null;
_next_start_index = Utility.DecodeMacFromBytesBE(_hashed_m_data_signature, _next_start_index, ref _decoded_signature_r_byte_array);
_next_start_index = Utility.DecodeMacFromBytesBE(_hashed_m_data_signature, _next_start_index, ref _decoded_signature_s_byte_array);
if (_decoded_signature_r_byte_array == null || _decoded_signature_r_byte_array.Length < 1)
throw new InvalidDataException("IsEncryptedSignatureVerified: The decoded DSA signature parameter 'r' byte array cannot be null/empty");
if (_decoded_signature_s_byte_array == null || _decoded_signature_s_byte_array.Length < 1)
throw new InvalidDataException("IsEncryptedSignatureVerified: The decoded DSA signature parameter 's' byte array cannot be null/empty");
/*Verify Signature*/
byte[] _hashed_m_data_byte_array = ComputeM(ake_keys, their_public_key_mpi_byte_array, key_pair.GetPublicKeyMpiBytes(), dsa_public_key_byte_array_encoded, _dh_kid_bytes, is_top_half_keys);
_is_verified = DSASigner.VerifySignature(_dsa_public_key_params, _hashed_m_data_byte_array, _decoded_signature_r_byte_array, _decoded_signature_s_byte_array);
}
catch (Exception ex)
{
_is_verified = false;
throw new InvalidDataException("IsEncryptedVerified:" + ex.ToString());
}
return _is_verified;
}