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
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
|
/*
* XMSS_PrivateKey.h
* (C) 2016 Matthias Gierlings
*
* Botan is released under the Simplified BSD License (see license.txt)
**/
#ifndef BOTAN_XMSS_PRIVATEKEY_H_
#define BOTAN_XMSS_PRIVATEKEY_H_
#include <cstddef>
#include <iterator>
#include <memory>
#include <botan/alg_id.h>
#include <botan/exceptn.h>
#include <botan/pk_keys.h>
#include <botan/types.h>
#include <botan/xmss_parameters.h>
#include <botan/xmss_publickey.h>
#include <botan/atomic.h>
#include <botan/xmss_common_ops.h>
#include <botan/xmss_wots_privatekey.h>
#include <botan/xmss_index_registry.h>
namespace Botan {
/**
* An XMSS: Extended Hash-Based Signature private key.
* The XMSS private key does not support the X509 and PKCS7 standard. Instead
* the raw format described in [1] is used.
*
* [1] XMSS: Extended Hash-Based Signatures,
* draft-itrf-cfrg-xmss-hash-based-signatures-06
* Release: July 2016.
* https://datatracker.ietf.org/doc/
* draft-irtf-cfrg-xmss-hash-based-signatures/?include_text=1
**/
class BOTAN_PUBLIC_API(2,0) XMSS_PrivateKey final : public virtual XMSS_PublicKey,
public XMSS_Common_Ops,
public virtual Private_Key
{
public:
/**
* Creates a new XMSS private key for the chosen XMSS signature method.
* New seeds for public/private key and pseudo random function input are
* generated using the provided RNG. The appropriate WOTS signature method
* will be automatically set based on the chosen XMSS signature method.
*
* @param xmss_algo_id Identifier for the selected XMSS signature method.
* @param rng A random number generator to use for key generation.
**/
XMSS_PrivateKey(XMSS_Parameters::xmss_algorithm_t xmss_algo_id,
RandomNumberGenerator& rng);
/**
* Creates an XMSS_PrivateKey from a byte sequence produced by
* raw_private_key().
*
* @param raw_key An XMSS private key serialized using raw_private_key().
**/
XMSS_PrivateKey(const secure_vector<uint8_t>& raw_key);
/**
* Creates a new XMSS private key for the chosen XMSS signature method
* using precomputed seeds for public/private keys and pseudo random
* function input. The appropriate WOTS signature method will be
* automatically set, based on the chosen XMSS signature method.
*
* @param xmss_algo_id Identifier for the selected XMSS signature method.
* @param idx_leaf Index of the next unused leaf.
* @param wots_priv_seed A seed to generate a Winternitz-One-Time-
* Signature private key from.
* @param prf a secret n-byte key sourced from a secure source
* of uniformly random data.
* @param root Root node of the binary hash tree.
* @param public_seed The public seed.
**/
XMSS_PrivateKey(XMSS_Parameters::xmss_algorithm_t xmss_algo_id,
size_t idx_leaf,
const secure_vector<uint8_t>& wots_priv_seed,
const secure_vector<uint8_t>& prf,
const secure_vector<uint8_t>& root,
const secure_vector<uint8_t>& public_seed)
: XMSS_PublicKey(xmss_algo_id, root, public_seed),
XMSS_Common_Ops(xmss_algo_id),
m_wots_priv_key(XMSS_PublicKey::m_xmss_params.ots_oid(),
public_seed,
wots_priv_seed),
m_prf(prf),
m_index_reg(XMSS_Index_Registry::get_instance())
{
set_unused_leaf_index(idx_leaf);
}
/**
* Retrieves the last unused leaf index of the private key. Reusing a leaf
* by utilizing leaf indices lower than the last unused leaf index will
* compromise security.
*
* @return Index of the last unused leaf.
**/
size_t unused_leaf_index() const
{
return *recover_global_leaf_index();
}
/**
* Sets the last unused leaf index of the private key. The leaf index
* will be updated automatically during every signing operation, and
* should not be set manually.
*
* @param idx Index of the last unused leaf.
**/
void set_unused_leaf_index(size_t idx)
{
if(idx >= (1ull << (XMSS_PublicKey::m_xmss_params.tree_height() - 1)))
{
throw Integrity_Failure("XMSS private key leaf index out of "
"bounds.");
}
else
{
std::atomic<size_t>& index =
static_cast<std::atomic<size_t>&>(*recover_global_leaf_index());
size_t current = 0;
do
{
current = index.load();
if(current > idx)
return;
}
while(!index.compare_exchange_strong(current, idx));
}
}
size_t reserve_unused_leaf_index()
{
size_t idx = (static_cast<std::atomic<size_t>&>(
*recover_global_leaf_index())).fetch_add(1);
if(idx >= (1ull << (XMSS_PublicKey::m_xmss_params.tree_height() - 1)))
{
throw Integrity_Failure("XMSS private key, one time signatures "
"exhausted.");
}
return idx;
}
/**
* Winternitz One Time Signature Scheme key utilized for signing
* operations.
*
* @return WOTS+ private key.
**/
const XMSS_WOTS_PrivateKey& wots_private_key() const
{
return m_wots_priv_key;
}
/**
* Winternitz One Time Signature Scheme key utilized for signing
* operations.
*
* @return WOTS+ private key.
**/
XMSS_WOTS_PrivateKey& wots_private_key()
{
return m_wots_priv_key;
}
const secure_vector<uint8_t>& prf() const
{
return m_prf;
}
secure_vector<uint8_t>& prf()
{
return m_prf;
}
void set_public_seed(
const secure_vector<uint8_t>& public_seed) override
{
m_public_seed = public_seed;
m_wots_priv_key.set_public_seed(public_seed);
}
void set_public_seed(secure_vector<uint8_t>&& public_seed) override
{
m_public_seed = std::move(public_seed);
m_wots_priv_key.set_public_seed(m_public_seed);
}
const secure_vector<uint8_t>& public_seed() const override
{
return m_public_seed;
}
std::unique_ptr<PK_Ops::Signature>
create_signature_op(RandomNumberGenerator&,
const std::string&,
const std::string& provider) const override;
secure_vector<uint8_t> private_key_bits() const override
{
return raw_private_key();
}
size_t size() const override
{
return XMSS_PublicKey::size() +
sizeof(uint64_t) +
2 * XMSS_PublicKey::m_xmss_params.element_size();
}
/**
* Generates a non standartized byte sequence representing the XMSS
* private key.
*
* @return byte sequence consisting of the following elements in order:
* 4-byte OID, n-byte root node, n-byte public seed,
* 8-byte unused leaf index, n-byte prf seed, n-byte private seed.
**/
secure_vector<uint8_t> raw_private_key() const;
/**
* Algorithm 9: "treeHash"
* Computes the internal n-byte nodes of a Merkle tree.
*
* @param start_idx The start index.
* @param target_node_height Height of the target node.
* @param adrs Address of the tree containing the target node.
*
* @return The root node of a tree of height target_node height with the
* leftmost leaf being the hash of the WOTS+ pk with index
* start_idx.
**/
secure_vector<uint8_t> tree_hash(
size_t start_idx,
size_t target_node_height,
XMSS_Address& adrs);
private:
/**
* Fetches shared unused leaf index fromt the index registry
**/
std::shared_ptr<Atomic<size_t>> recover_global_leaf_index() const;
XMSS_WOTS_PrivateKey m_wots_priv_key;
secure_vector<uint8_t> m_prf;
XMSS_Index_Registry& m_index_reg;
};
}
#endif
|
