1 files changed, 195 insertions, 0 deletions
diff --git a/src/add_tweakeysequences/lilliput-ae-i.c b/src/add_tweakeysequences/lilliput-ae-i.c
new file mode 100644
index 0000000..b1758c9
--- /dev/null
+++ b/src/add_tweakeysequences/lilliput-ae-i.c
@@ -0,0 +1,195 @@
+#include <stdbool.h>
+#include <stdint.h>
+#include <string.h>
+
+#include "ae-common.h"
+#include "cipher.h"
+#include "lilliput-ae.h"
+
+
+static const uint8_t _0n[BLOCK_BYTES] = {
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+};
+
+
+static void _fill_msg_tweak(
+    uint8_t       prefix,
+    const uint8_t N[NONCE_BYTES],
+    uint64_t      block_nb,
+    uint8_t       tweak[TWEAK_BYTES]
+)
+{
+    /* The 192-bit tweak is filled as follows:
+     *
+     * - bits   1- 68: block number
+     *          1- 64: actual 64-bit block number
+     *         64- 68: 0-padding
+     * - bits  67-188: nonce
+     * - bits 189-192: constant 4-bit prefix
+     */
+
+    for (size_t i=0; i<sizeof(block_nb); i++)
+    {
+        uint64_t mask = (uint64_t)0xff << 8*i;
+        uint8_t b = (mask & block_nb) >> 8*i;
+
+        tweak[i] = b;
+    }
+
+    tweak[sizeof(block_nb)] = lower_nibble(N[0]) << 4;
+
+    for (size_t i=1; i<NONCE_BYTES; i++)
+    {
+        tweak[sizeof(block_nb)+i] = lower_nibble(N[i]) << 4 ^ upper_nibble(N[i-1]);
+    }
+
+    tweak[TWEAK_BYTES-1] = prefix << 4 ^ upper_nibble(N[NONCE_BYTES-1]);
+}
+
+static void _encrypt_message(
+    const uint8_t key[KEY_BYTES],
+    size_t        M_len,
+    const uint8_t M[M_len],
+    const uint8_t N[NONCE_BYTES],
+    uint8_t       C[M_len+BLOCK_BYTES],
+    uint8_t       Final[BLOCK_BYTES]
+)
+{
+    size_t l = M_len / BLOCK_BYTES;
+    size_t rest = M_len % BLOCK_BYTES;
+
+    uint8_t tweak[TWEAK_BYTES];
+    uint8_t checksum[BLOCK_BYTES];
+
+    memset(tweak, 0, TWEAK_BYTES);
+    memset(checksum, 0, BLOCK_BYTES);
+
+    for (size_t j=0; j<l; j++)
+    {
+        xor_into(checksum, &M[j*BLOCK_BYTES]);
+        _fill_msg_tweak(0x0, N, j, tweak);
+        encrypt(key, tweak, &M[j*BLOCK_BYTES], &C[j*BLOCK_BYTES]);
+    }
+
+    if (rest == 0)
+    {
+        _fill_msg_tweak(0x1, N, l-1, tweak);
+        encrypt(key, tweak, checksum, Final);
+    }
+    else
+    {
+        uint8_t M_rest[BLOCK_BYTES];
+        uint8_t Pad[BLOCK_BYTES];
+
+        pad10(rest, &M[l*BLOCK_BYTES], M_rest);
+        xor_into(checksum, M_rest);
+
+        _fill_msg_tweak(0x4, N, l, tweak);
+        encrypt(key, tweak, _0n, Pad);
+        xor_arrays(rest, &C[l*BLOCK_BYTES], &M[l*BLOCK_BYTES], Pad);
+
+        _fill_msg_tweak(0x5, N, l, tweak);
+        encrypt(key, tweak, checksum, Final);
+    }
+}
+
+static void _decrypt_message(
+    const uint8_t key[KEY_BYTES],
+    size_t        C_len,
+    const uint8_t C[C_len],
+    const uint8_t N[NONCE_BYTES],
+    uint8_t       M[C_len],
+    uint8_t       Final[BLOCK_BYTES]
+)
+{
+    size_t l = C_len / BLOCK_BYTES;
+    size_t rest = C_len % BLOCK_BYTES;
+
+    uint8_t tweak[TWEAK_BYTES];
+    uint8_t checksum[BLOCK_BYTES];
+
+    memset(tweak, 0, TWEAK_BYTES);
+    memset(checksum, 0, BLOCK_BYTES);
+
+    for (size_t j=0; j<l; j++)
+    {
+        _fill_msg_tweak(0x0, N, j, tweak);
+        decrypt(key, tweak, &C[j*BLOCK_BYTES], &M[j*BLOCK_BYTES]);
+        xor_into(checksum, &M[j*BLOCK_BYTES]);
+    }
+
+    if (rest == 0)
+    {
+        _fill_msg_tweak(0x1, N, l-1, tweak);
+        encrypt(key, tweak, checksum, Final);
+    }
+    else
+    {
+        uint8_t M_rest[BLOCK_BYTES];
+        uint8_t Pad[BLOCK_BYTES];
+
+        _fill_msg_tweak(0x4, N, l, tweak);
+        encrypt(key, tweak, _0n, Pad);
+        xor_arrays(rest, &M[l*BLOCK_BYTES], &C[l*BLOCK_BYTES], Pad);
+
+        pad10(rest, &M[l*BLOCK_BYTES], M_rest);
+        xor_into(checksum, M_rest);
+
+        _fill_msg_tweak(0x5, N, l, tweak);
+        encrypt(key, tweak, checksum, Final);
+    }
+}
+
+static void _generate_tag(
+    const uint8_t Final[BLOCK_BYTES],
+    const uint8_t Auth[BLOCK_BYTES],
+    uint8_t       tag[TAG_BYTES]
+)
+{
+    xor_arrays(TAG_BYTES, tag, Final, Auth);
+}
+
+
+void lilliput_ae_encrypt(
+    size_t        message_len,
+    const uint8_t message[message_len],
+    size_t        auth_data_len,
+    const uint8_t auth_data[auth_data_len],
+    const uint8_t key[KEY_BYTES],
+    const uint8_t nonce[NONCE_BYTES],
+    uint8_t       ciphertext[message_len],
+    uint8_t       tag[TAG_BYTES]
+)
+{
+    uint8_t auth[BLOCK_BYTES];
+    process_associated_data(key, auth_data_len, auth_data, auth);
+
+    uint8_t final[BLOCK_BYTES];
+    _encrypt_message(key, message_len, message, nonce, ciphertext, final);
+
+    _generate_tag(final, auth, tag);
+}
+
+bool lilliput_ae_decrypt(
+    size_t        ciphertext_len,
+    const uint8_t ciphertext[ciphertext_len],
+    size_t        auth_data_len,
+    const uint8_t auth_data[auth_data_len],
+    const uint8_t key[KEY_BYTES],
+    const uint8_t nonce[NONCE_BYTES],
+    const uint8_t tag[TAG_BYTES],
+    uint8_t       message[ciphertext_len]
+)
+{
+    uint8_t auth[BLOCK_BYTES];
+    process_associated_data(key, auth_data_len, auth_data, auth);
+
+    uint8_t final[BLOCK_BYTES];
+    _decrypt_message(key, ciphertext_len, ciphertext, nonce, message, final);
+
+    uint8_t effective_tag[TAG_BYTES];
+    _generate_tag(final, auth, effective_tag);
+
+    return memcmp(tag, effective_tag, TAG_BYTES) == 0;
+}