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
|
// Package ecc implements a generic interface for ECDH, ECDSA, and EdDSA.
package ecc
import (
"crypto/subtle"
"io"
"github.com/ProtonMail/go-crypto/openpgp/errors"
x448lib "github.com/cloudflare/circl/dh/x448"
)
type x448 struct{}
func NewX448() *x448 {
return &x448{}
}
func (c *x448) GetCurveName() string {
return "x448"
}
// MarshalBytePoint encodes the public point from native format, adding the prefix.
// See https://datatracker.ietf.org/doc/html/draft-ietf-openpgp-crypto-refresh-06#section-5.5.5.6
func (c *x448) MarshalBytePoint(point []byte) []byte {
return append([]byte{0x40}, point...)
}
// UnmarshalBytePoint decodes a point from prefixed format to native.
// See https://datatracker.ietf.org/doc/html/draft-ietf-openpgp-crypto-refresh-06#section-5.5.5.6
func (c *x448) UnmarshalBytePoint(point []byte) []byte {
if len(point) != x448lib.Size+1 {
return nil
}
return point[1:]
}
// MarshalByteSecret encoded a scalar from native format to prefixed.
// See https://datatracker.ietf.org/doc/html/draft-ietf-openpgp-crypto-refresh-06#section-5.5.5.6.1.2
func (c *x448) MarshalByteSecret(d []byte) []byte {
return append([]byte{0x40}, d...)
}
// UnmarshalByteSecret decodes a scalar from prefixed format to native.
// See https://datatracker.ietf.org/doc/html/draft-ietf-openpgp-crypto-refresh-06#section-5.5.5.6.1.2
func (c *x448) UnmarshalByteSecret(d []byte) []byte {
if len(d) != x448lib.Size+1 {
return nil
}
// Store without prefix
return d[1:]
}
func (c *x448) generateKeyPairBytes(rand io.Reader) (sk, pk x448lib.Key, err error) {
if _, err = rand.Read(sk[:]); err != nil {
return
}
x448lib.KeyGen(&pk, &sk)
return
}
func (c *x448) GenerateECDH(rand io.Reader) (point []byte, secret []byte, err error) {
priv, pub, err := c.generateKeyPairBytes(rand)
if err != nil {
return
}
return pub[:], priv[:], nil
}
func (c *x448) Encaps(rand io.Reader, point []byte) (ephemeral, sharedSecret []byte, err error) {
var pk, ss x448lib.Key
seed, e, err := c.generateKeyPairBytes(rand)
if err != nil {
return nil, nil, err
}
copy(pk[:], point)
x448lib.Shared(&ss, &seed, &pk)
return e[:], ss[:], nil
}
func (c *x448) Decaps(ephemeral, secret []byte) (sharedSecret []byte, err error) {
var ss, sk, e x448lib.Key
copy(sk[:], secret)
copy(e[:], ephemeral)
x448lib.Shared(&ss, &sk, &e)
return ss[:], nil
}
func (c *x448) ValidateECDH(point []byte, secret []byte) error {
var sk, pk, expectedPk x448lib.Key
copy(pk[:], point)
copy(sk[:], secret)
x448lib.KeyGen(&expectedPk, &sk)
if subtle.ConstantTimeCompare(expectedPk[:], pk[:]) == 0 {
return errors.KeyInvalidError("ecc: invalid curve25519 public point")
}
return nil
}
|
