From 4fefe35fd63842b827016acecfadae891d0da953 Mon Sep 17 00:00:00 2001
From: Kévin Le Gouguec <kevin.legouguec@airbus.com>
Date: Tue, 27 Nov 2018 10:37:56 +0100
Subject: Extraction du traitement des données authentifiées
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Commun à ΘCB3 et SCT-2.
---
 src/ae-common.h      | 61 +++++++++++++++++++++++++++++++++++++++++++++++++
 src/lilliput-ae-i.c  | 64 ++--------------------------------------------------
 src/lilliput-ae-ii.c | 13 +++--------
 3 files changed, 66 insertions(+), 72 deletions(-)

(limited to 'src')

diff --git a/src/ae-common.h b/src/ae-common.h
index 6343f98..da5d04d 100644
--- a/src/ae-common.h
+++ b/src/ae-common.h
@@ -65,5 +65,66 @@ static inline void pad10(size_t X_len, const uint8_t X[X_len], uint8_t padded[BL
     }
 }
 
+static inline void _fill_ad_tweak(
+    uint8_t  prefix,
+    uint64_t block_nb,
+    uint8_t  tweak[TWEAK_BYTES]
+)
+{
+    /* The t-bit tweak is filled as follows:
+     *
+     * - bits [  1, t-4]: block number
+     *        [  1,  64]: actual 64-bit block number
+     *        [ 65, t-4]: 0-padding
+     * - bits [t-3,   t]: 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;
+    }
+
+    /* Assume padding bytes have already been memset to 0. */
+
+    tweak[TWEAK_BYTES-1] |= prefix << 4;
+}
+
+static void process_associated_data(
+    const uint8_t key[KEY_BYTES],
+    size_t        A_len,
+    const uint8_t A[A_len],
+    uint8_t       Auth[BLOCK_BYTES]
+)
+{
+    uint8_t Ek_Ai[BLOCK_BYTES];
+    uint8_t tweak[TWEAK_BYTES];
+
+    memset(tweak, 0, TWEAK_BYTES);
+    memset(Auth, 0, BLOCK_BYTES);
+
+    size_t l_a = A_len / BLOCK_BYTES;
+    size_t rest = A_len % BLOCK_BYTES;
+
+    for (size_t i=0; i<l_a; i++)
+    {
+        _fill_ad_tweak(0x2, i, tweak);
+        encrypt(key, tweak, &A[i*BLOCK_BYTES], Ek_Ai);
+        xor_into(Auth, Ek_Ai);
+    }
+
+    if (rest != 0)
+    {
+        uint8_t A_rest[BLOCK_BYTES];
+        pad10(rest, &A[l_a*BLOCK_BYTES], A_rest);
+        _fill_ad_tweak(0x6, l_a, tweak);
+        encrypt(key, tweak, A_rest, Ek_Ai);
+        xor_into(Auth, Ek_Ai);
+    }
+}
+
+
 
 #endif /* AE_COMMON_H */
diff --git a/src/lilliput-ae-i.c b/src/lilliput-ae-i.c
index 5d1a630..b1758c9 100644
--- a/src/lilliput-ae-i.c
+++ b/src/lilliput-ae-i.c
@@ -13,33 +13,6 @@ static const uint8_t _0n[BLOCK_BYTES] = {
 };
 
 
-static void _fill_ad_tweak(
-    uint8_t  prefix,
-    uint64_t block_nb,
-    uint8_t  tweak[TWEAK_BYTES]
-)
-{
-    /* The 192-bit tweak is filled as follows:
-     *
-     * - bits   1-188: block number
-     *          1- 64: actual 64-bit block number
-     *         65-188: 0-padding
-     * - 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;
-    }
-
-    /* Assume padding bytes have already been memset to 0. */
-
-    tweak[TWEAK_BYTES-1] |= prefix << 4;
-}
-
 static void _fill_msg_tweak(
     uint8_t       prefix,
     const uint8_t N[NONCE_BYTES],
@@ -74,39 +47,6 @@ static void _fill_msg_tweak(
     tweak[TWEAK_BYTES-1] = prefix << 4 ^ upper_nibble(N[NONCE_BYTES-1]);
 }
 
-static void _process_associated_data(
-    const uint8_t key[KEY_BYTES],
-    size_t        A_len,
-    const uint8_t A[A_len],
-    uint8_t       Auth[BLOCK_BYTES]
-)
-{
-    uint8_t Ek_Ai[BLOCK_BYTES];
-    uint8_t tweak[TWEAK_BYTES];
-
-    memset(tweak, 0, TWEAK_BYTES);
-    memset(Auth, 0, BLOCK_BYTES);
-
-    size_t l_a = A_len / BLOCK_BYTES;
-    size_t rest = A_len % BLOCK_BYTES;
-
-    for (size_t i=0; i<l_a; i++)
-    {
-        _fill_ad_tweak(0x2, i, tweak);
-        encrypt(key, tweak, &A[i*BLOCK_BYTES], Ek_Ai);
-        xor_into(Auth, Ek_Ai);
-    }
-
-    if (rest != 0)
-    {
-        uint8_t A_rest[BLOCK_BYTES];
-        pad10(rest, &A[l_a*BLOCK_BYTES], A_rest);
-        _fill_ad_tweak(0x6, l_a, tweak);
-        encrypt(key, tweak, A_rest, Ek_Ai);
-        xor_into(Auth, Ek_Ai);
-    }
-}
-
 static void _encrypt_message(
     const uint8_t key[KEY_BYTES],
     size_t        M_len,
@@ -223,7 +163,7 @@ void lilliput_ae_encrypt(
 )
 {
     uint8_t auth[BLOCK_BYTES];
-    _process_associated_data(key, auth_data_len, auth_data, auth);
+    process_associated_data(key, auth_data_len, auth_data, auth);
 
     uint8_t final[BLOCK_BYTES];
     _encrypt_message(key, message_len, message, nonce, ciphertext, final);
@@ -243,7 +183,7 @@ bool lilliput_ae_decrypt(
 )
 {
     uint8_t auth[BLOCK_BYTES];
-    _process_associated_data(key, auth_data_len, auth_data, auth);
+    process_associated_data(key, auth_data_len, auth_data, auth);
 
     uint8_t final[BLOCK_BYTES];
     _decrypt_message(key, ciphertext_len, ciphertext, nonce, message, final);
diff --git a/src/lilliput-ae-ii.c b/src/lilliput-ae-ii.c
index 23ff27e..fc50211 100644
--- a/src/lilliput-ae-ii.c
+++ b/src/lilliput-ae-ii.c
@@ -2,18 +2,11 @@
 #include <stdint.h>
 #include <string.h>
 
+#include "ae-common.h"
 #include "cipher.h"
 #include "lilliput-ae.h"
 
 
-static void _process_associated_data(
-    const uint8_t key[KEY_BYTES],
-    size_t        A_len,
-    const uint8_t A[A_len],
-    uint8_t       Auth[BLOCK_BYTES]
-)
-{
-}
 
 static void _generate_tag(
     const uint8_t key[KEY_BYTES],
@@ -61,7 +54,7 @@ void lilliput_ae_encrypt(
 )
 {
     uint8_t auth[BLOCK_BYTES];
-    _process_associated_data(key, auth_data_len, auth_data, auth);
+    process_associated_data(key, auth_data_len, auth_data, auth);
 
     _generate_tag(key, message_len, message, nonce, auth, tag);
 
@@ -82,7 +75,7 @@ bool lilliput_ae_decrypt(
     _decrypt_message(key, ciphertext_len, ciphertext, nonce, tag, message);
 
     uint8_t auth[BLOCK_BYTES];
-    _process_associated_data(key, auth_data_len, auth_data, auth);
+    process_associated_data(key, auth_data_len, auth_data, auth);
 
     uint8_t effective_tag[TAG_BYTES];
     _generate_tag(key, ciphertext_len, message, nonce, auth, effective_tag);
-- 
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