1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
|
/*
Implementation of the Lilliput-AE tweakable block cipher.
Author: Kévin Le Gouguec, 2019.
For more information, feedback or questions, refer to our website:
https://paclido.fr/lilliput-ae
To the extent possible under law, the implementer has waived all copyright
and related or neighboring rights to the source code in this file.
http://creativecommons.org/publicdomain/zero/1.0/
---
This file provides functions used by both authenticated encryption modes.
*/
#ifndef LILLIPUT_AE_UTILS_H
#define LILLIPUT_AE_UTILS_H
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include "cipher.h"
#include "constants.h"
static inline uint8_t upper_nibble(uint8_t i)
{
return i >> 4;
}
static inline uint8_t lower_nibble(uint8_t i)
{
return i & 0x0f;
}
static inline void encrypt(const uint8_t K[KEY_BYTES],
const uint8_t T[TWEAK_BYTES],
const uint8_t M[BLOCK_BYTES],
uint8_t C[BLOCK_BYTES])
{
lilliput_tbc_encrypt(K, T, M, C);
}
static inline void decrypt(const uint8_t K[KEY_BYTES],
const uint8_t T[TWEAK_BYTES],
const uint8_t C[BLOCK_BYTES],
uint8_t M[BLOCK_BYTES])
{
lilliput_tbc_decrypt(K, T, C, M);
}
static inline void xor_into(uint8_t dest[BLOCK_BYTES], const uint8_t src[BLOCK_BYTES])
{
for (size_t i=0; i<BLOCK_BYTES; i++)
dest[i] ^= src[i];
}
static inline void xor_arrays(size_t len, uint8_t out[len], const uint8_t a[len], const uint8_t b[len])
{
for (size_t i=0; i<len; i++)
out[i] = a[i] ^ b[i];
}
static inline void pad10(size_t X_len, const uint8_t X[X_len], uint8_t padded[BLOCK_BYTES])
{
/* pad10*(X) = X || 1 || 0^{n-|X|-1} */
/* Assume that len<BLOCK_BYTES. */
size_t pad_len = BLOCK_BYTES-X_len;
memcpy(padded+pad_len, X, X_len);
padded[pad_len-1] = 0x80;
if (pad_len > 1)
{
memset(padded, 0, pad_len-1);
}
}
static inline void fill_index_tweak(
uint8_t prefix,
uint64_t block_index,
uint8_t tweak[TWEAK_BYTES]
)
{
/* The t-bit tweak is filled as follows:
*
* - bits [ 1, t-4]: block index
* [ 1, 64]: actual 64-bit block index
* [ 65, t-4]: 0-padding
* - bits [t-3, t]: constant 4-bit prefix
*/
for (size_t i=0; i<sizeof(block_index); i++)
{
tweak[i] = block_index >> 8*i & 0xff;
}
/* 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_index_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_index_tweak(0x6, l_a, tweak);
encrypt(key, tweak, A_rest, Ek_Ai);
xor_into(Auth, Ek_Ai);
}
}
#endif /* LILLIPUT_AE_UTILS_H */
|
