-
Notifications
You must be signed in to change notification settings - Fork 17.4k
/
shake.go
174 lines (150 loc) · 5.37 KB
/
shake.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
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
169
170
171
172
173
174
// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package sha3
// This file defines the ShakeHash interface, and provides
// functions for creating SHAKE and cSHAKE instances, as well as utility
// functions for hashing bytes to arbitrary-length output.
//
//
// SHAKE implementation is based on FIPS PUB 202 [1]
// cSHAKE implementations is based on NIST SP 800-185 [2]
//
// [1] https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.202.pdf
// [2] https://doi.org/10.6028/NIST.SP.800-185
import (
"encoding/binary"
"hash"
"io"
)
// ShakeHash defines the interface to hash functions that support
// arbitrary-length output. When used as a plain [hash.Hash], it
// produces minimum-length outputs that provide full-strength generic
// security.
type ShakeHash interface {
hash.Hash
// Read reads more output from the hash; reading affects the hash's
// state. (ShakeHash.Read is thus very different from Hash.Sum)
// It never returns an error, but subsequent calls to Write or Sum
// will panic.
io.Reader
// Clone returns a copy of the ShakeHash in its current state.
Clone() ShakeHash
}
// cSHAKE specific context
type cshakeState struct {
*state // SHA-3 state context and Read/Write operations
// initBlock is the cSHAKE specific initialization set of bytes. It is initialized
// by newCShake function and stores concatenation of N followed by S, encoded
// by the method specified in 3.3 of [1].
// It is stored here in order for Reset() to be able to put context into
// initial state.
initBlock []byte
}
// Consts for configuring initial SHA-3 state
const (
dsbyteShake = 0x1f
dsbyteCShake = 0x04
rate128 = 168
rate256 = 136
)
func bytepad(input []byte, w int) []byte {
// leftEncode always returns max 9 bytes
buf := make([]byte, 0, 9+len(input)+w)
buf = append(buf, leftEncode(uint64(w))...)
buf = append(buf, input...)
padlen := w - (len(buf) % w)
return append(buf, make([]byte, padlen)...)
}
func leftEncode(value uint64) []byte {
var b [9]byte
binary.BigEndian.PutUint64(b[1:], value)
// Trim all but last leading zero bytes
i := byte(1)
for i < 8 && b[i] == 0 {
i++
}
// Prepend number of encoded bytes
b[i-1] = 9 - i
return b[i-1:]
}
func newCShake(N, S []byte, rate, outputLen int, dsbyte byte) ShakeHash {
c := cshakeState{state: &state{rate: rate, outputLen: outputLen, dsbyte: dsbyte}}
// leftEncode returns max 9 bytes
c.initBlock = make([]byte, 0, 9*2+len(N)+len(S))
c.initBlock = append(c.initBlock, leftEncode(uint64(len(N)*8))...)
c.initBlock = append(c.initBlock, N...)
c.initBlock = append(c.initBlock, leftEncode(uint64(len(S)*8))...)
c.initBlock = append(c.initBlock, S...)
c.Write(bytepad(c.initBlock, c.rate))
return &c
}
// Reset resets the hash to initial state.
func (c *cshakeState) Reset() {
c.state.Reset()
c.Write(bytepad(c.initBlock, c.rate))
}
// Clone returns copy of a cSHAKE context within its current state.
func (c *cshakeState) Clone() ShakeHash {
b := make([]byte, len(c.initBlock))
copy(b, c.initBlock)
return &cshakeState{state: c.clone(), initBlock: b}
}
// Clone returns copy of SHAKE context within its current state.
func (c *state) Clone() ShakeHash {
return c.clone()
}
// NewShake128 creates a new SHAKE128 variable-output-length ShakeHash.
// Its generic security strength is 128 bits against all attacks if at
// least 32 bytes of its output are used.
func NewShake128() ShakeHash {
return newShake128()
}
// NewShake256 creates a new SHAKE256 variable-output-length ShakeHash.
// Its generic security strength is 256 bits against all attacks if
// at least 64 bytes of its output are used.
func NewShake256() ShakeHash {
return newShake256()
}
func newShake128Generic() *state {
return &state{rate: rate128, outputLen: 32, dsbyte: dsbyteShake}
}
func newShake256Generic() *state {
return &state{rate: rate256, outputLen: 64, dsbyte: dsbyteShake}
}
// NewCShake128 creates a new instance of cSHAKE128 variable-output-length ShakeHash,
// a customizable variant of SHAKE128.
// N is used to define functions based on cSHAKE, it can be empty when plain cSHAKE is
// desired. S is a customization byte string used for domain separation - two cSHAKE
// computations on same input with different S yield unrelated outputs.
// When N and S are both empty, this is equivalent to NewShake128.
func NewCShake128(N, S []byte) ShakeHash {
if len(N) == 0 && len(S) == 0 {
return NewShake128()
}
return newCShake(N, S, rate128, 32, dsbyteCShake)
}
// NewCShake256 creates a new instance of cSHAKE256 variable-output-length ShakeHash,
// a customizable variant of SHAKE256.
// N is used to define functions based on cSHAKE, it can be empty when plain cSHAKE is
// desired. S is a customization byte string used for domain separation - two cSHAKE
// computations on same input with different S yield unrelated outputs.
// When N and S are both empty, this is equivalent to NewShake256.
func NewCShake256(N, S []byte) ShakeHash {
if len(N) == 0 && len(S) == 0 {
return NewShake256()
}
return newCShake(N, S, rate256, 64, dsbyteCShake)
}
// ShakeSum128 writes an arbitrary-length digest of data into hash.
func ShakeSum128(hash, data []byte) {
h := NewShake128()
h.Write(data)
h.Read(hash)
}
// ShakeSum256 writes an arbitrary-length digest of data into hash.
func ShakeSum256(hash, data []byte) {
h := NewShake256()
h.Write(data)
h.Read(hash)
}