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
164
165
166
167
168
use crate::FieldBytes;
use elliptic_curve::{
subtle::{Choice, ConditionallySelectable, ConstantTimeEq, CtOption},
zeroize::Zeroize,
};
#[cfg(target_pointer_width = "32")]
use super::field_10x26::FieldElement10x26 as FieldElementUnsafeImpl;
#[cfg(target_pointer_width = "64")]
use super::field_5x52::FieldElement5x52 as FieldElementUnsafeImpl;
#[derive(Clone, Copy, Debug)]
pub struct FieldElementImpl {
value: FieldElementUnsafeImpl,
magnitude: u32,
normalized: bool,
}
impl FieldElementImpl {
const fn new_normalized(value: &FieldElementUnsafeImpl) -> Self {
Self {
value: *value,
magnitude: 1,
normalized: true,
}
}
const fn new_weak_normalized(value: &FieldElementUnsafeImpl) -> Self {
Self {
value: *value,
magnitude: 1,
normalized: false,
}
}
fn new(value: &FieldElementUnsafeImpl, magnitude: u32) -> Self {
debug_assert!(magnitude <= FieldElementUnsafeImpl::max_magnitude());
Self {
value: *value,
magnitude,
normalized: false,
}
}
pub const fn zero() -> Self {
Self::new_normalized(&FieldElementUnsafeImpl::zero())
}
pub const fn one() -> Self {
Self::new_normalized(&FieldElementUnsafeImpl::one())
}
pub(crate) const fn from_bytes_unchecked(bytes: &[u8; 32]) -> Self {
let value = FieldElementUnsafeImpl::from_bytes_unchecked(bytes);
Self::new_normalized(&value)
}
pub fn from_bytes(bytes: &FieldBytes) -> CtOption<Self> {
let value = FieldElementUnsafeImpl::from_bytes(bytes);
CtOption::map(value, |x| Self::new_normalized(&x))
}
pub fn to_bytes(self) -> FieldBytes {
debug_assert!(self.normalized);
self.value.to_bytes()
}
pub fn normalize_weak(&self) -> Self {
Self::new_weak_normalized(&self.value.normalize_weak())
}
pub fn normalize(&self) -> Self {
Self::new_normalized(&self.value.normalize())
}
pub fn normalizes_to_zero(&self) -> Choice {
self.value.normalizes_to_zero()
}
pub fn is_zero(&self) -> Choice {
debug_assert!(self.normalized);
self.value.is_zero()
}
pub fn is_odd(&self) -> Choice {
debug_assert!(self.normalized);
self.value.is_odd()
}
pub fn negate(&self, magnitude: u32) -> Self {
debug_assert!(self.magnitude <= magnitude);
let new_magnitude = magnitude + 1;
debug_assert!(new_magnitude <= FieldElementUnsafeImpl::max_magnitude());
Self::new(&(self.value.negate(magnitude)), new_magnitude)
}
pub fn add(&self, rhs: &Self) -> Self {
let new_magnitude = self.magnitude + rhs.magnitude;
debug_assert!(new_magnitude <= FieldElementUnsafeImpl::max_magnitude());
Self::new(&(self.value.add(&(rhs.value))), new_magnitude)
}
pub fn mul_single(&self, rhs: u32) -> Self {
let new_magnitude = self.magnitude * rhs;
debug_assert!(new_magnitude <= FieldElementUnsafeImpl::max_magnitude());
Self::new(&(self.value.mul_single(rhs)), new_magnitude)
}
pub fn mul(&self, rhs: &Self) -> Self {
debug_assert!(self.magnitude <= 8);
debug_assert!(rhs.magnitude <= 8);
Self::new_weak_normalized(&(self.value.mul(&(rhs.value))))
}
pub fn square(&self) -> Self {
debug_assert!(self.magnitude <= 8);
Self::new_weak_normalized(&(self.value.square()))
}
}
impl Default for FieldElementImpl {
fn default() -> Self {
Self::zero()
}
}
impl ConditionallySelectable for FieldElementImpl {
fn conditional_select(a: &Self, b: &Self, choice: Choice) -> Self {
let new_normalized = if bool::from(choice) {
b.normalized
} else {
a.normalized
};
Self {
value: FieldElementUnsafeImpl::conditional_select(&(a.value), &(b.value), choice),
magnitude: u32::conditional_select(&(a.magnitude), &(b.magnitude), choice),
normalized: new_normalized,
}
}
}
impl ConstantTimeEq for FieldElementImpl {
fn ct_eq(&self, other: &Self) -> Choice {
self.value.ct_eq(&(other.value))
& self.magnitude.ct_eq(&(other.magnitude))
& Choice::from((self.normalized == other.normalized) as u8)
}
}
impl Zeroize for FieldElementImpl {
fn zeroize(&mut self) {
self.value.zeroize();
self.magnitude.zeroize();
self.normalized.zeroize();
}
}