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
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
|
#include <stddef.h>
#include <stdint.h>
#include "kyber512r3_indcpa.h"
#include "kyber512r3_indcpa_avx2.h"
#include "kyber512r3_params.h"
#include "kyber512r3_symmetric.h"
#include "pq-crypto/s2n_pq.h"
#include "pq-crypto/s2n_pq_random.h"
#include "tls/s2n_kem.h"
#include "utils/s2n_safety.h"
S2N_ENSURE_PORTABLE_OPTIMIZATIONS
/*************************************************
* Name: crypto_kem_keypair
*
* Description: Generates public and private key
* for CCA-secure Kyber key encapsulation mechanism
*
* Arguments: - unsigned char *pk: pointer to output public key
* (an already allocated array of S2N_KYBER_512_R3_PUBLIC_KEY_BYTES bytes)
* - unsigned char *sk: pointer to output private key
* (an already allocated array of S2N_KYBER_512_R3_SECRET_KEY_BYTES bytes)
*
* Returns 0 (success)
**************************************************/
int s2n_kyber_512_r3_crypto_kem_keypair(const struct s2n_kem *kem, uint8_t *pk, uint8_t *sk)
{
POSIX_ENSURE(s2n_pq_is_enabled(), S2N_ERR_PQ_DISABLED);
#if defined(S2N_KYBER512R3_AVX2_BMI2)
if (s2n_kyber512r3_is_avx2_bmi2_enabled()) {
POSIX_GUARD(indcpa_keypair_avx2(pk, sk));
} else
#endif
{
POSIX_GUARD(indcpa_keypair(pk, sk));
}
for (size_t i = 0; i < S2N_KYBER_512_R3_INDCPA_PUBLICKEYBYTES; i++) {
sk[i + S2N_KYBER_512_R3_INDCPA_SECRETKEYBYTES] = pk[i];
}
sha3_256(sk + S2N_KYBER_512_R3_SECRET_KEY_BYTES - 2 * S2N_KYBER_512_R3_SYMBYTES, pk, S2N_KYBER_512_R3_PUBLIC_KEY_BYTES);
/* Value z for pseudo-random output on reject */
POSIX_GUARD_RESULT(s2n_get_random_bytes(sk + S2N_KYBER_512_R3_SECRET_KEY_BYTES - S2N_KYBER_512_R3_SYMBYTES, S2N_KYBER_512_R3_SYMBYTES));
return S2N_SUCCESS;
}
/*************************************************
* Name: crypto_kem_enc
*
* Description: Generates cipher text and shared
* secret for given public key
*
* Arguments: - unsigned char *ct: pointer to output cipher text
* (an already allocated array of S2N_KYBER_512_R3_CIPHERTEXT_BYTES bytes)
* - unsigned char *ss: pointer to output shared secret
* (an already allocated array of S2N_KYBER_512_R3_SHARED_SECRET_BYTES bytes)
* - const unsigned char *pk: pointer to input public key
* (an already allocated array of S2N_KYBER_512_R3_PUBLIC_KEY_BYTES bytes)
*
* Returns 0 (success)
**************************************************/
int s2n_kyber_512_r3_crypto_kem_enc(const struct s2n_kem *kem, uint8_t *ct, uint8_t *ss,
const uint8_t *pk)
{
POSIX_ENSURE(s2n_pq_is_enabled(), S2N_ERR_PQ_DISABLED);
uint8_t buf[2 * S2N_KYBER_512_R3_SYMBYTES];
/* Will contain key, coins */
uint8_t kr[2 * S2N_KYBER_512_R3_SYMBYTES];
POSIX_GUARD_RESULT(s2n_get_random_bytes(buf, S2N_KYBER_512_R3_SYMBYTES));
/* Don't release system RNG output */
sha3_256(buf, buf, S2N_KYBER_512_R3_SYMBYTES);
/* Multitarget countermeasure for coins + contributory KEM */
sha3_256(buf + S2N_KYBER_512_R3_SYMBYTES, pk, S2N_KYBER_512_R3_PUBLIC_KEY_BYTES);
sha3_512(kr, buf, 2 * S2N_KYBER_512_R3_SYMBYTES);
/* coins are in kr+S2N_KYBER_512_R3_SYMBYTES */
#if defined(S2N_KYBER512R3_AVX2_BMI2)
if (s2n_kyber512r3_is_avx2_bmi2_enabled()) {
indcpa_enc_avx2(ct, buf, pk, kr + S2N_KYBER_512_R3_SYMBYTES);
} else
#endif
{
indcpa_enc(ct, buf, pk, kr + S2N_KYBER_512_R3_SYMBYTES);
}
/* overwrite coins in kr with H(c) */
sha3_256(kr + S2N_KYBER_512_R3_SYMBYTES, ct, S2N_KYBER_512_R3_CIPHERTEXT_BYTES);
/* hash concatenation of pre-k and H(c) to k */
shake256(ss, S2N_KYBER_512_R3_SSBYTES, kr, 2 * S2N_KYBER_512_R3_SYMBYTES);
return S2N_SUCCESS;
}
/*************************************************
* Name: crypto_kem_dec
*
* Description: Generates shared secret for given
* cipher text and private key
*
* Arguments: - unsigned char *ss: pointer to output shared secret
* (an already allocated array of S2N_KYBER_512_R3_SHARED_SECRET_BYTES bytes)
* - const unsigned char *ct: pointer to input cipher text
* (an already allocated array of S2N_KYBER_512_R3_CIPHERTEXT_BYTES bytes)
* - const unsigned char *sk: pointer to input private key
* (an already allocated array of S2N_KYBER_512_R3_SECRET_KEY_BYTES bytes)
*
* Returns 0.
*
* On failure, ss will contain a pseudo-random value.
**************************************************/
int s2n_kyber_512_r3_crypto_kem_dec(const struct s2n_kem *kem, uint8_t *ss, const uint8_t *ct,
const uint8_t *sk)
{
POSIX_ENSURE(s2n_pq_is_enabled(), S2N_ERR_PQ_DISABLED);
uint8_t buf[2 * S2N_KYBER_512_R3_SYMBYTES];
/* Will contain key, coins */
uint8_t kr[2 * S2N_KYBER_512_R3_SYMBYTES];
uint8_t cmp[S2N_KYBER_512_R3_CIPHERTEXT_BYTES];
const uint8_t *pk = sk + S2N_KYBER_512_R3_INDCPA_SECRETKEYBYTES;
#if defined(S2N_KYBER512R3_AVX2_BMI2)
if (s2n_kyber512r3_is_avx2_bmi2_enabled()) {
indcpa_dec_avx2(buf, ct, sk);
} else
#endif
{
indcpa_dec(buf, ct, sk);
}
/* Multitarget countermeasure for coins + contributory KEM */
for (size_t i = 0; i < S2N_KYBER_512_R3_SYMBYTES; i++) {
buf[S2N_KYBER_512_R3_SYMBYTES + i] = sk[S2N_KYBER_512_R3_SECRET_KEY_BYTES - 2 * S2N_KYBER_512_R3_SYMBYTES + i];
}
sha3_512(kr, buf, 2 * S2N_KYBER_512_R3_SYMBYTES);
/* coins are in kr+S2N_KYBER_512_R3_SYMBYTES */
#if defined(S2N_KYBER512R3_AVX2_BMI2)
if (s2n_kyber512r3_is_avx2_bmi2_enabled()) {
indcpa_enc_avx2(cmp, buf, pk, kr + S2N_KYBER_512_R3_SYMBYTES);
} else
#endif
{
indcpa_enc(cmp, buf, pk, kr + S2N_KYBER_512_R3_SYMBYTES);
}
/* If ct and cmp are equal (dont_copy = 1), decryption has succeeded and we do NOT overwrite pre-k below.
* If ct and cmp are not equal (dont_copy = 0), decryption fails and we do overwrite pre-k. */
int dont_copy = s2n_constant_time_equals(ct, cmp, S2N_KYBER_512_R3_CIPHERTEXT_BYTES);
/* overwrite coins in kr with H(c) */
sha3_256(kr + S2N_KYBER_512_R3_SYMBYTES, ct, S2N_KYBER_512_R3_CIPHERTEXT_BYTES);
/* Overwrite pre-k with z on re-encryption failure */
POSIX_GUARD(s2n_constant_time_copy_or_dont(kr, sk + S2N_KYBER_512_R3_SECRET_KEY_BYTES - S2N_KYBER_512_R3_SYMBYTES,
S2N_KYBER_512_R3_SYMBYTES, dont_copy));
/* hash concatenation of pre-k and H(c) to k */
shake256(ss, S2N_KYBER_512_R3_SSBYTES, kr, 2 * S2N_KYBER_512_R3_SYMBYTES);
return S2N_SUCCESS;
}
|
