-
Notifications
You must be signed in to change notification settings - Fork 0
/
curve.go
106 lines (86 loc) · 2.08 KB
/
curve.go
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
package ed25519
import (
"crypto/rand"
"encoding/hex"
"github.com/jtejido/spake2plus/internal/suite"
"math/big"
)
var cofactor = new(big.Int).SetInt64(8)
var prime, _ = new(big.Int).SetString("57896044618658097711785492504343953926634992332820282019728792003956564819949", 10)
var primeOrder, _ = new(big.Int).SetString("7237005577332262213973186563042994240857116359379907606001950938285454250989", 10)
type curve struct {
}
func (c curve) String() string {
return "Ed25519"
}
func (c curve) Scalar() suite.Scalar {
return &scalar{}
}
func (c curve) Element() suite.Element {
P := new(point)
return P
}
func (c curve) M() suite.Element {
str, err := hex.DecodeString("d048032c6ea0b6d697ddc2e86bda85a33adac920f1bf18e1b0c6d166a5cecdaf")
if err != nil {
panic(err)
}
point := c.Element()
if err := point.FromBytes(str); err != nil {
panic(err)
}
return point
}
func (c curve) N() suite.Element {
str, err := hex.DecodeString("d3bfb518f44f3430f29d0c92af503865a1ed3281dc69b35dd868ba85f886c4ab")
if err != nil {
panic(err)
}
point := c.Element()
if err := point.FromBytes(str); err != nil {
panic(err)
}
return point
}
func (c curve) RandomElement() (suite.Element, error) {
sc, err := c.RandomScalar()
return c.Element().ScalarMult(sc, nil), err
}
func (c curve) RandomScalar() (suite.Scalar, error) {
var b [64]byte
_, err := rand.Read(b[:])
if err != nil {
return nil, err
}
var randomScalar scalar
// reduce to mod order
scReduce(&randomScalar, &b)
return &randomScalar, nil
}
func (c curve) ScalarLen() int {
return 32
}
func (c curve) ElementLen() int {
return 32
}
func (c curve) Order() *big.Int {
return primeOrder
}
func (c curve) CofactorScalar() suite.Scalar {
var sc scalar
buf := make([]byte, 32)
copy(buf[:1], cofactor.Bytes())
copy(sc[:], reverse(buf))
return &sc
}
func (c curve) ClearCofactor(elem suite.Element) suite.Element {
return c.Element().ScalarMult(c.CofactorScalar(), elem)
}
func reverse(p []byte) []byte {
q := make([]byte, len(p))
for i := 0; 2*i < len(p); i++ {
j := len(p) - 1 - i
q[i], q[j] = p[j], p[i]
}
return q[:]
}