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
use crate::ibe::cgw::{CipherText, Msg, CGW, USK_BYTES as CPA_USK_BYTES};
use crate::ibe::IBE;
use crate::kem::{Error, SharedSecret, IBKEM};
use crate::util::*;
use crate::Compress;
use arrayref::{array_refs, mut_array_refs};
use group::Group;
use rand::{CryptoRng, Rng};
use subtle::{ConstantTimeEq, CtOption};
pub use crate::ibe::cgw::{PublicKey, SecretKey, CT_BYTES, MSG_BYTES, PK_BYTES, SK_BYTES};
pub const USK_BYTES: usize = CPA_USK_BYTES + ID_BYTES;
#[derive(Debug, Clone, Copy, PartialEq)]
pub struct UserSecretKey {
usk: crate::ibe::cgw::UserSecretKey,
id: Identity,
}
impl Compress for UserSecretKey {
const OUTPUT_SIZE: usize = USK_BYTES;
type Output = [u8; Self::OUTPUT_SIZE];
fn to_bytes(&self) -> [u8; USK_BYTES] {
let mut buf = [0u8; USK_BYTES];
let (usk, id) = mut_array_refs![&mut buf, CPA_USK_BYTES, ID_BYTES];
*usk = self.usk.to_bytes();
id.copy_from_slice(&self.id.0);
buf
}
fn from_bytes(bytes: &[u8; USK_BYTES]) -> CtOption<Self> {
let (usk, rid) = array_refs![&bytes, CPA_USK_BYTES, ID_BYTES];
let usk = crate::ibe::cgw::UserSecretKey::from_bytes(usk);
let id = Identity(*rid);
usk.map(|usk| UserSecretKey { usk, id })
}
}
#[derive(Debug, Clone, Copy)]
pub struct CGWFO;
impl IBKEM for CGWFO {
const IDENTIFIER: &'static str = "cgwfo";
type Pk = PublicKey;
type Sk = SecretKey;
type Usk = UserSecretKey;
type Ct = CipherText;
type Id = Identity;
const PK_BYTES: usize = PK_BYTES;
const USK_BYTES: usize = USK_BYTES;
const SK_BYTES: usize = SK_BYTES;
const CT_BYTES: usize = CT_BYTES;
fn setup<R: Rng + CryptoRng>(rng: &mut R) -> (PublicKey, SecretKey) {
CGW::setup(rng)
}
fn extract_usk<R: Rng + CryptoRng>(
_pk: Option<&PublicKey>,
sk: &SecretKey,
id: &Identity,
rng: &mut R,
) -> UserSecretKey {
let usk = CGW::extract_usk(None, sk, id, rng);
UserSecretKey { usk, id: *id }
}
fn encaps<R: Rng + CryptoRng>(
pk: &PublicKey,
id: &Identity,
rng: &mut R,
) -> (CipherText, SharedSecret) {
let m = Msg::random(rng);
let mut pre_coins = [0u8; MSG_BYTES + ID_BYTES];
pre_coins[..MSG_BYTES].copy_from_slice(&m.to_bytes());
pre_coins[MSG_BYTES..].copy_from_slice(&id.0);
let coins = sha3_512(&pre_coins);
let ct = CGW::encrypt(pk, id, &m, &coins);
(ct, SharedSecret::from(&m))
}
fn decaps(
opk: Option<&PublicKey>,
usk: &UserSecretKey,
c: &CipherText,
) -> Result<SharedSecret, Error> {
let pk = opk.unwrap();
let m = CGW::decrypt(&usk.usk, c);
let mut pre_coins = [0u8; MSG_BYTES + ID_BYTES];
pre_coins[..MSG_BYTES].copy_from_slice(&m.to_bytes());
pre_coins[MSG_BYTES..].copy_from_slice(&usk.id.0);
let coins = sha3_512(&pre_coins);
let c2 = CGW::encrypt(pk, &usk.id, &m, &coins);
if c.ct_eq(&c2).into() {
Ok(SharedSecret::from(&m))
} else {
Err(Error)
}
}
}
#[cfg(feature = "mkem")]
impl crate::kem::mkem::MultiRecipient for CGWFO {}
#[cfg(test)]
mod tests {
use super::*;
use crate::Derive;
test_kem!(CGWFO);
#[cfg(feature = "mkem")]
test_multi_kem!(CGWFO);
}