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13 package ed25519
14
15 import (
16 "bytes"
17 "crypto"
18 "crypto/internal/edwards25519"
19 cryptorand "crypto/rand"
20 "crypto/sha512"
21 "errors"
22 "io"
23 "strconv"
24 )
25
26 const (
27
28 PublicKeySize = 32
29
30 PrivateKeySize = 64
31
32 SignatureSize = 64
33
34 SeedSize = 32
35 )
36
37
38 type PublicKey []byte
39
40
41
42
43
44 func (pub PublicKey) Equal(x crypto.PublicKey) bool {
45 xx, ok := x.(PublicKey)
46 if !ok {
47 return false
48 }
49 return bytes.Equal(pub, xx)
50 }
51
52
53 type PrivateKey []byte
54
55
56 func (priv PrivateKey) Public() crypto.PublicKey {
57 publicKey := make([]byte, PublicKeySize)
58 copy(publicKey, priv[32:])
59 return PublicKey(publicKey)
60 }
61
62
63 func (priv PrivateKey) Equal(x crypto.PrivateKey) bool {
64 xx, ok := x.(PrivateKey)
65 if !ok {
66 return false
67 }
68 return bytes.Equal(priv, xx)
69 }
70
71
72
73
74 func (priv PrivateKey) Seed() []byte {
75 seed := make([]byte, SeedSize)
76 copy(seed, priv[:32])
77 return seed
78 }
79
80
81
82
83
84
85 func (priv PrivateKey) Sign(rand io.Reader, message []byte, opts crypto.SignerOpts) (signature []byte, err error) {
86 if opts.HashFunc() != crypto.Hash(0) {
87 return nil, errors.New("ed25519: cannot sign hashed message")
88 }
89
90 return Sign(priv, message), nil
91 }
92
93
94
95 func GenerateKey(rand io.Reader) (PublicKey, PrivateKey, error) {
96 if rand == nil {
97 rand = cryptorand.Reader
98 }
99
100 seed := make([]byte, SeedSize)
101 if _, err := io.ReadFull(rand, seed); err != nil {
102 return nil, nil, err
103 }
104
105 privateKey := NewKeyFromSeed(seed)
106 publicKey := make([]byte, PublicKeySize)
107 copy(publicKey, privateKey[32:])
108
109 return publicKey, privateKey, nil
110 }
111
112
113
114
115
116 func NewKeyFromSeed(seed []byte) PrivateKey {
117
118 privateKey := make([]byte, PrivateKeySize)
119 newKeyFromSeed(privateKey, seed)
120 return privateKey
121 }
122
123 func newKeyFromSeed(privateKey, seed []byte) {
124 if l := len(seed); l != SeedSize {
125 panic("ed25519: bad seed length: " + strconv.Itoa(l))
126 }
127
128 h := sha512.Sum512(seed)
129 s, err := edwards25519.NewScalar().SetBytesWithClamping(h[:32])
130 if err != nil {
131 panic("ed25519: internal error: setting scalar failed")
132 }
133 A := (&edwards25519.Point{}).ScalarBaseMult(s)
134
135 publicKey := A.Bytes()
136
137 copy(privateKey, seed)
138 copy(privateKey[32:], publicKey)
139 }
140
141
142
143 func Sign(privateKey PrivateKey, message []byte) []byte {
144
145
146 signature := make([]byte, SignatureSize)
147 sign(signature, privateKey, message)
148 return signature
149 }
150
151 func sign(signature, privateKey, message []byte) {
152 if l := len(privateKey); l != PrivateKeySize {
153 panic("ed25519: bad private key length: " + strconv.Itoa(l))
154 }
155 seed, publicKey := privateKey[:SeedSize], privateKey[SeedSize:]
156
157 h := sha512.Sum512(seed)
158 s, err := edwards25519.NewScalar().SetBytesWithClamping(h[:32])
159 if err != nil {
160 panic("ed25519: internal error: setting scalar failed")
161 }
162 prefix := h[32:]
163
164 mh := sha512.New()
165 mh.Write(prefix)
166 mh.Write(message)
167 messageDigest := make([]byte, 0, sha512.Size)
168 messageDigest = mh.Sum(messageDigest)
169 r, err := edwards25519.NewScalar().SetUniformBytes(messageDigest)
170 if err != nil {
171 panic("ed25519: internal error: setting scalar failed")
172 }
173
174 R := (&edwards25519.Point{}).ScalarBaseMult(r)
175
176 kh := sha512.New()
177 kh.Write(R.Bytes())
178 kh.Write(publicKey)
179 kh.Write(message)
180 hramDigest := make([]byte, 0, sha512.Size)
181 hramDigest = kh.Sum(hramDigest)
182 k, err := edwards25519.NewScalar().SetUniformBytes(hramDigest)
183 if err != nil {
184 panic("ed25519: internal error: setting scalar failed")
185 }
186
187 S := edwards25519.NewScalar().MultiplyAdd(k, s, r)
188
189 copy(signature[:32], R.Bytes())
190 copy(signature[32:], S.Bytes())
191 }
192
193
194
195 func Verify(publicKey PublicKey, message, sig []byte) bool {
196 if l := len(publicKey); l != PublicKeySize {
197 panic("ed25519: bad public key length: " + strconv.Itoa(l))
198 }
199
200 if len(sig) != SignatureSize || sig[63]&224 != 0 {
201 return false
202 }
203
204 A, err := (&edwards25519.Point{}).SetBytes(publicKey)
205 if err != nil {
206 return false
207 }
208
209 kh := sha512.New()
210 kh.Write(sig[:32])
211 kh.Write(publicKey)
212 kh.Write(message)
213 hramDigest := make([]byte, 0, sha512.Size)
214 hramDigest = kh.Sum(hramDigest)
215 k, err := edwards25519.NewScalar().SetUniformBytes(hramDigest)
216 if err != nil {
217 panic("ed25519: internal error: setting scalar failed")
218 }
219
220 S, err := edwards25519.NewScalar().SetCanonicalBytes(sig[32:])
221 if err != nil {
222 return false
223 }
224
225
226 minusA := (&edwards25519.Point{}).Negate(A)
227 R := (&edwards25519.Point{}).VarTimeDoubleScalarBaseMult(k, minusA, S)
228
229 return bytes.Equal(sig[:32], R.Bytes())
230 }
231
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