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Merge pull request #136 from cppalliance/reverse_aes
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Reverse AES functions
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@mborland
mborland authored Dec 3, 2024
2 parents 1ff5bf8 + 32391ae commit 4c4a248
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Showing 2 changed files with 216 additions and 2 deletions.
208 changes: 207 additions & 1 deletion include/boost/crypt/aes/detail/cipher.hpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,25 @@ BOOST_CRYPT_INLINE_CONSTEXPR boost::crypt::array<boost::crypt::uint8_t, 256> sbo
0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16
};

BOOST_CRYPT_INLINE_CONSTEXPR boost::crypt::array<boost::crypt::uint8_t, 256> rsbox = {
0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25,
0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92,
0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06,
0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b,
0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e,
0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b,
0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,
0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef,
0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d
};

BOOST_CRYPT_INLINE_CONSTEXPR boost::crypt::array<boost::crypt::uint8_t, 11> Rcon = {
0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36
};
Expand All @@ -57,6 +76,7 @@ class cipher

boost::crypt::array<boost::crypt::array<boost::crypt::uint8_t, Nb>, Nb> state {};
boost::crypt::array<boost::crypt::uint8_t, key_expansion_size> round_key {};
bool initialized {false};

BOOST_CRYPT_GPU_ENABLED constexpr auto rot_word(boost::crypt::array<boost::crypt::uint8_t, 4>& temp) noexcept -> void;

Expand All @@ -67,20 +87,34 @@ class cipher

BOOST_CRYPT_GPU_ENABLED constexpr auto sub_bytes() noexcept -> void;

BOOST_CRYPT_GPU_ENABLED constexpr auto inv_sub_bytes() noexcept -> void;

BOOST_CRYPT_GPU_ENABLED constexpr auto shift_rows() noexcept -> void;

BOOST_CRYPT_GPU_ENABLED constexpr auto inv_shift_rows() noexcept -> void;

BOOST_CRYPT_GPU_ENABLED constexpr auto xtimes(boost::crypt::uint8_t b) noexcept -> boost::crypt::uint8_t;

BOOST_CRYPT_GPU_ENABLED constexpr auto mix_columns() noexcept -> void;

BOOST_CRYPT_GPU_ENABLED constexpr auto gf28_multiply(boost::crypt::uint8_t x, boost::crypt::uint8_t y) noexcept -> boost::crypt::uint8_t;

BOOST_CRYPT_GPU_ENABLED constexpr auto inv_mix_columns() noexcept -> void;

BOOST_CRYPT_GPU_ENABLED constexpr auto add_round_key(boost::crypt::uint8_t round) noexcept -> void;

template <typename ForwardIter>
BOOST_CRYPT_GPU_ENABLED constexpr auto cipher_impl(ForwardIter buffer) noexcept -> void;

template <typename ForwardIter>
BOOST_CRYPT_GPU_ENABLED constexpr auto inv_cipher_impl(ForwardIter buffer) noexcept -> void;

template <typename ForwardIter>
BOOST_CRYPT_GPU_ENABLED constexpr auto encrypt_impl(ForwardIter buffer, boost::crypt::size_t buffer_size, const boost::crypt::integral_constant<aes::cipher_mode, aes::cipher_mode::ecb>&) noexcept -> void;

template <typename ForwardIter>
BOOST_CRYPT_GPU_ENABLED constexpr auto decrypt_impl(ForwardIter buffer, boost::crypt::size_t buffer_size, const boost::crypt::integral_constant<aes::cipher_mode, aes::cipher_mode::ecb>&) noexcept -> void;

public:

BOOST_CRYPT_GPU_ENABLED constexpr cipher() noexcept = default;
Expand All @@ -98,6 +132,9 @@ class cipher
template <boost::crypt::aes::cipher_mode mode, typename ForwardIter>
BOOST_CRYPT_GPU_ENABLED constexpr auto encrypt(ForwardIter data, boost::crypt::size_t data_length = Nk) noexcept -> boost::crypt::state;

template <boost::crypt::aes::cipher_mode mode, typename ForwardIter>
BOOST_CRYPT_GPU_ENABLED constexpr auto decrypt(ForwardIter data, boost::crypt::size_t data_length = Nk) noexcept -> boost::crypt::state;

BOOST_CRYPT_GPU_ENABLED constexpr auto destroy() noexcept;
};

Expand All @@ -115,6 +152,7 @@ constexpr auto cipher<Nr>::init(ForwardIter key, boost::crypt::size_t key_length
}

key_expansion(key, key_length);
initialized = true;
return state::success;
}

Expand Down Expand Up @@ -147,7 +185,49 @@ constexpr auto cipher<Nr>::cipher_impl(ForwardIter buffer) noexcept -> void
BOOST_CRYPT_ASSERT(round == Nr);
sub_bytes();
shift_rows();
add_round_key(Nr);
add_round_key(round);

// Write the cipher text back
offset = 0U;
for (boost::crypt::size_t i {}; i < Nb; ++i)
{
for (boost::crypt::size_t j {}; j < Nb; ++j)
{
buffer[offset++] = static_cast<boost::crypt::uint8_t>(state[i][j]);
}
}
}

template <boost::crypt::size_t Nr>
template <typename ForwardIter>
constexpr auto cipher<Nr>::inv_cipher_impl(ForwardIter buffer) noexcept -> void
{
// Write the buffer to state and then perform operations
boost::crypt::ptrdiff_t offset {};
for (boost::crypt::size_t i {}; i < Nb; ++i)
{
for (boost::crypt::size_t j {}; j < Nb; ++j)
{
state[i][j] = static_cast<boost::crypt::uint8_t>(buffer[offset++]);
}
}

boost::crypt::uint8_t round {Nr};

add_round_key(round);

for (--round; round > 0; --round)
{
inv_shift_rows();
inv_sub_bytes();
add_round_key(round);
inv_mix_columns();
}

BOOST_CRYPT_ASSERT(round == 0);
inv_shift_rows();
inv_sub_bytes();
add_round_key(round);

// Write the cipher text back
offset = 0U;
Expand All @@ -174,6 +254,20 @@ constexpr auto cipher<Nr>::encrypt_impl(ForwardIter buffer, boost::crypt::size_t
}
}

template <boost::crypt::size_t Nr>
template <typename ForwardIter>
constexpr auto cipher<Nr>::decrypt_impl(ForwardIter buffer, boost::crypt::size_t buffer_size,
const integral_constant<aes::cipher_mode, aes::cipher_mode::ecb>&) noexcept -> void
{
constexpr auto state_complete_size {Nb * Nb};
while (buffer_size >= state_complete_size)
{
inv_cipher_impl(buffer);
buffer_size -= state_complete_size;
buffer += static_cast<boost::crypt::ptrdiff_t>(state_complete_size);
}
}

template <boost::crypt::size_t Nr>
template <boost::crypt::aes::cipher_mode mode, typename ForwardIter>
constexpr auto cipher<Nr>::encrypt(ForwardIter data, boost::crypt::size_t data_length) noexcept -> boost::crypt::state
Expand All @@ -182,11 +276,32 @@ constexpr auto cipher<Nr>::encrypt(ForwardIter data, boost::crypt::size_t data_l
{
return state::null;
}
else if (!initialized)
{
return state::uninitialized;
}

encrypt_impl(data, data_length, boost::crypt::integral_constant<aes::cipher_mode, mode>{});
return state::success;
}

template <boost::crypt::size_t Nr>
template <boost::crypt::aes::cipher_mode mode, typename ForwardIter>
constexpr auto cipher<Nr>::decrypt(ForwardIter data, boost::crypt::size_t data_length) noexcept -> boost::crypt::state
{
if (utility::is_null(data) || data_length == 0U)
{
return state::null;
}
else if (!initialized)
{
return state::uninitialized;
}

decrypt_impl(data, data_length, boost::crypt::integral_constant<aes::cipher_mode, mode>{});
return state::success;
}

template <boost::crypt::size_t Nr>
constexpr auto cipher<Nr>::destroy() noexcept
{
Expand All @@ -198,6 +313,7 @@ constexpr auto cipher<Nr>::destroy() noexcept
}
}
round_key.fill(0x00);
initialized = false;
}

// The transformation of words in which the four bytes of the word
Expand Down Expand Up @@ -297,6 +413,19 @@ BOOST_CRYPT_GPU_ENABLED constexpr auto cipher<Nr>::sub_bytes() noexcept -> void
}
}

// The inverse of sub_bytes (above), in which rsbox is applied to each byte
template <boost::crypt::size_t Nr>
BOOST_CRYPT_GPU_ENABLED constexpr auto cipher<Nr>::inv_sub_bytes() noexcept -> void
{
for (auto& line : state)
{
for (auto& val : line)
{
val = rsbox[val];
}
}
}

// The transformation of the state in which the last three rows are
// cyclically shifted by different offsets.
template <boost::crypt::size_t Nr>
Expand Down Expand Up @@ -325,6 +454,36 @@ BOOST_CRYPT_GPU_ENABLED constexpr auto cipher<Nr>::shift_rows() noexcept -> void
state[1][3] = temp;
}

// inv_shift_rows in the inverse of shift rows (above).
// In particular, the bytes in the last three rows of the state are shifted cyclically
//
// s'_r,c = s_r,(c-r) mod 4 for 0 <= r < 4 and 0 <= c < 4
template <boost::crypt::size_t Nr>
BOOST_CRYPT_GPU_ENABLED constexpr auto cipher<Nr>::inv_shift_rows() noexcept -> void
{
boost::crypt::uint8_t temp {};

temp = state[3][1];
state[3][1] = state[2][1];
state[2][1] = state[1][1];
state[1][1] = state[0][1];
state[0][1] = temp;

temp = state[0][2];
state[0][2] = state[2][2];
state[2][2] = temp;

temp = state[1][2];
state[1][2] = state[3][2];
state[3][2] = temp;

temp = state[0][3];
state[0][3] = state[1][3];
state[1][3] = state[2][3];
state[2][3] = state[3][3];
state[3][3] = temp;
}

// The transformation of bytes in which the polynomial representation
// of the input byte is multiplied by x, modulo m(x), to produce the
// polynomial representation of the output byte.
Expand Down Expand Up @@ -376,8 +535,55 @@ BOOST_CRYPT_GPU_ENABLED constexpr auto cipher<Nr>::mix_columns() noexcept -> voi
}
}

template <boost::crypt::size_t Nr>
constexpr auto cipher<Nr>::gf28_multiply(boost::crypt::uint8_t x, boost::crypt::uint8_t y) noexcept -> boost::crypt::uint8_t
{
#if defined(__GNUC__) && __GNUC__ >= 7 && __GNUC__ <= 9
# pragma GCC diagnostic push
# pragma GCC diagnostic ignored "-Wsign-conversion"
#endif

return static_cast<boost::crypt::uint8_t>(
((y & 1U) * x) ^
((y >> 1U & 1U) * xtimes(x)) ^
((y >> 2U & 1U) * xtimes(xtimes(x))) ^
((y >> 3U & 1U) * xtimes(xtimes(xtimes(x)))) ^
((y >> 4U & 1U) * xtimes(xtimes(xtimes(xtimes(x)))))
);

#if defined(__GNUC__) && __GNUC__ >= 7 && __GNUC__ <= 9
# pragma GCC diagnostic pop
#endif
}

template <boost::crypt::size_t Nr>
BOOST_CRYPT_GPU_ENABLED constexpr auto cipher<Nr>::inv_mix_columns() noexcept -> void
{
for (auto& column : state)
{
const auto s0 {column[0]};
const auto s1 {column[1]};
const auto s2 {column[2]};
const auto s3 {column[3]};

// s'_0,c = ({0e} * s_0,c) ^ ({0b} * s_1,c) ^ ({0d} * s_2,c) ^ ({09} * s_3,c)
column[0] = gf28_multiply(s0, 0x0e) ^ gf28_multiply(s1, 0x0b) ^ gf28_multiply(s2, 0x0d) ^ gf28_multiply(s3, 0x09);

// s'_1,c = ({09} * s_0,c) ^ ({0e} * s_1,c) ^ ({0b} * s_2,c) ^ ({0d} * s_3,c)
column[1] = gf28_multiply(s0, 0x09) ^ gf28_multiply(s1, 0x0e) ^ gf28_multiply(s2, 0x0b) ^ gf28_multiply(s3, 0x0d);

// s`_2,c = ({0d} * s_0,c) ^ ({09} * s_1,c) ^ ({0e} * s_2,c) ^ ({0b} * s_3,c)
column[2] = gf28_multiply(s0, 0x0d) ^ gf28_multiply(s1, 0x09) ^ gf28_multiply(s2, 0x0e) ^ gf28_multiply(s3, 0x0b);

// s`_3,c = ({0b} * s_0,c) ^ ({0d} * s_1,c) ^ ({09} * s_2,c) ^ ({0e} * s_3,c)
column[3] = gf28_multiply(s0, 0x0b) ^ gf28_multiply(s1, 0x0d) ^ gf28_multiply(s2, 0x09) ^ gf28_multiply(s3, 0x0e);
}
}

// The transformation of the state in which a round key is combined
// with the state.
//
// Add round_key is its own inverse so there is no separate inverse function
template <boost::crypt::size_t Nr>
constexpr auto cipher<Nr>::add_round_key(boost::crypt::uint8_t round) noexcept -> void
{
Expand Down
10 changes: 9 additions & 1 deletion test/test_aes.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -19,16 +19,24 @@ void basic_aes128_test()
0x31, 0x31, 0x98, 0xa2, 0xe0, 0x37, 0x07, 0x34
};

const auto original_message {plaintext};

boost::crypt::aes128 gen;
BOOST_TEST(gen.init(key, key.size()) == boost::crypt::state::success);
BOOST_TEST(gen.encrypt<boost::crypt::aes::cipher_mode::ecb>(plaintext.begin(), plaintext.size()) == boost::crypt::state::success);

boost::crypt::array<uint8_t, 16> validation_1 = {
const boost::crypt::array<uint8_t, 16> validation_1 = {
0x39, 0x25, 0x84, 0x1d, 0x02, 0xdc, 0x09, 0xfb,
0xdc, 0x11, 0x85, 0x97, 0x19, 0x6a, 0x0b, 0x32,
};

BOOST_TEST(plaintext == validation_1);

BOOST_TEST(gen.decrypt<boost::crypt::aes::cipher_mode::ecb>(plaintext.begin(), plaintext.size()) == boost::crypt::state::success);

BOOST_TEST(plaintext == original_message);

gen.destroy();
}

int main()
Expand Down

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