aboutsummaryrefslogtreecommitdiff
path: root/src/key.cpp
blob: 512790252af74ed9a675e6abc9316bf860a91f91 (plain)
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
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
// Copyright (c) 2009-2022 The Bitcoin Core developers
// Copyright (c) 2017 The Zcash developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <key.h>

#include <crypto/common.h>
#include <crypto/hmac_sha512.h>
#include <hash.h>
#include <random.h>

#include <secp256k1.h>
#include <secp256k1_ellswift.h>
#include <secp256k1_extrakeys.h>
#include <secp256k1_recovery.h>
#include <secp256k1_schnorrsig.h>

static secp256k1_context* secp256k1_context_sign = nullptr;

/** These functions are taken from the libsecp256k1 distribution and are very ugly. */

/**
 * This parses a format loosely based on a DER encoding of the ECPrivateKey type from
 * section C.4 of SEC 1 <https://www.secg.org/sec1-v2.pdf>, with the following caveats:
 *
 * * The octet-length of the SEQUENCE must be encoded as 1 or 2 octets. It is not
 *   required to be encoded as one octet if it is less than 256, as DER would require.
 * * The octet-length of the SEQUENCE must not be greater than the remaining
 *   length of the key encoding, but need not match it (i.e. the encoding may contain
 *   junk after the encoded SEQUENCE).
 * * The privateKey OCTET STRING is zero-filled on the left to 32 octets.
 * * Anything after the encoding of the privateKey OCTET STRING is ignored, whether
 *   or not it is validly encoded DER.
 *
 * out32 must point to an output buffer of length at least 32 bytes.
 */
int ec_seckey_import_der(const secp256k1_context* ctx, unsigned char *out32, const unsigned char *seckey, size_t seckeylen) {
    const unsigned char *end = seckey + seckeylen;
    memset(out32, 0, 32);
    /* sequence header */
    if (end - seckey < 1 || *seckey != 0x30u) {
        return 0;
    }
    seckey++;
    /* sequence length constructor */
    if (end - seckey < 1 || !(*seckey & 0x80u)) {
        return 0;
    }
    ptrdiff_t lenb = *seckey & ~0x80u; seckey++;
    if (lenb < 1 || lenb > 2) {
        return 0;
    }
    if (end - seckey < lenb) {
        return 0;
    }
    /* sequence length */
    ptrdiff_t len = seckey[lenb-1] | (lenb > 1 ? seckey[lenb-2] << 8 : 0u);
    seckey += lenb;
    if (end - seckey < len) {
        return 0;
    }
    /* sequence element 0: version number (=1) */
    if (end - seckey < 3 || seckey[0] != 0x02u || seckey[1] != 0x01u || seckey[2] != 0x01u) {
        return 0;
    }
    seckey += 3;
    /* sequence element 1: octet string, up to 32 bytes */
    if (end - seckey < 2 || seckey[0] != 0x04u) {
        return 0;
    }
    ptrdiff_t oslen = seckey[1];
    seckey += 2;
    if (oslen > 32 || end - seckey < oslen) {
        return 0;
    }
    memcpy(out32 + (32 - oslen), seckey, oslen);
    if (!secp256k1_ec_seckey_verify(ctx, out32)) {
        memset(out32, 0, 32);
        return 0;
    }
    return 1;
}

/**
 * This serializes to a DER encoding of the ECPrivateKey type from section C.4 of SEC 1
 * <https://www.secg.org/sec1-v2.pdf>. The optional parameters and publicKey fields are
 * included.
 *
 * seckey must point to an output buffer of length at least CKey::SIZE bytes.
 * seckeylen must initially be set to the size of the seckey buffer. Upon return it
 * will be set to the number of bytes used in the buffer.
 * key32 must point to a 32-byte raw private key.
 */
int ec_seckey_export_der(const secp256k1_context *ctx, unsigned char *seckey, size_t *seckeylen, const unsigned char *key32, bool compressed) {
    assert(*seckeylen >= CKey::SIZE);
    secp256k1_pubkey pubkey;
    size_t pubkeylen = 0;
    if (!secp256k1_ec_pubkey_create(ctx, &pubkey, key32)) {
        *seckeylen = 0;
        return 0;
    }
    if (compressed) {
        static const unsigned char begin[] = {
            0x30,0x81,0xD3,0x02,0x01,0x01,0x04,0x20
        };
        static const unsigned char middle[] = {
            0xA0,0x81,0x85,0x30,0x81,0x82,0x02,0x01,0x01,0x30,0x2C,0x06,0x07,0x2A,0x86,0x48,
            0xCE,0x3D,0x01,0x01,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
            0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
            0xFF,0xFF,0xFE,0xFF,0xFF,0xFC,0x2F,0x30,0x06,0x04,0x01,0x00,0x04,0x01,0x07,0x04,
            0x21,0x02,0x79,0xBE,0x66,0x7E,0xF9,0xDC,0xBB,0xAC,0x55,0xA0,0x62,0x95,0xCE,0x87,
            0x0B,0x07,0x02,0x9B,0xFC,0xDB,0x2D,0xCE,0x28,0xD9,0x59,0xF2,0x81,0x5B,0x16,0xF8,
            0x17,0x98,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
            0xFF,0xFF,0xFF,0xFF,0xFE,0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,0xBF,0xD2,0x5E,
            0x8C,0xD0,0x36,0x41,0x41,0x02,0x01,0x01,0xA1,0x24,0x03,0x22,0x00
        };
        unsigned char *ptr = seckey;
        memcpy(ptr, begin, sizeof(begin)); ptr += sizeof(begin);
        memcpy(ptr, key32, 32); ptr += 32;
        memcpy(ptr, middle, sizeof(middle)); ptr += sizeof(middle);
        pubkeylen = CPubKey::COMPRESSED_SIZE;
        secp256k1_ec_pubkey_serialize(ctx, ptr, &pubkeylen, &pubkey, SECP256K1_EC_COMPRESSED);
        ptr += pubkeylen;
        *seckeylen = ptr - seckey;
        assert(*seckeylen == CKey::COMPRESSED_SIZE);
    } else {
        static const unsigned char begin[] = {
            0x30,0x82,0x01,0x13,0x02,0x01,0x01,0x04,0x20
        };
        static const unsigned char middle[] = {
            0xA0,0x81,0xA5,0x30,0x81,0xA2,0x02,0x01,0x01,0x30,0x2C,0x06,0x07,0x2A,0x86,0x48,
            0xCE,0x3D,0x01,0x01,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
            0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
            0xFF,0xFF,0xFE,0xFF,0xFF,0xFC,0x2F,0x30,0x06,0x04,0x01,0x00,0x04,0x01,0x07,0x04,
            0x41,0x04,0x79,0xBE,0x66,0x7E,0xF9,0xDC,0xBB,0xAC,0x55,0xA0,0x62,0x95,0xCE,0x87,
            0x0B,0x07,0x02,0x9B,0xFC,0xDB,0x2D,0xCE,0x28,0xD9,0x59,0xF2,0x81,0x5B,0x16,0xF8,
            0x17,0x98,0x48,0x3A,0xDA,0x77,0x26,0xA3,0xC4,0x65,0x5D,0xA4,0xFB,0xFC,0x0E,0x11,
            0x08,0xA8,0xFD,0x17,0xB4,0x48,0xA6,0x85,0x54,0x19,0x9C,0x47,0xD0,0x8F,0xFB,0x10,
            0xD4,0xB8,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
            0xFF,0xFF,0xFF,0xFF,0xFE,0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,0xBF,0xD2,0x5E,
            0x8C,0xD0,0x36,0x41,0x41,0x02,0x01,0x01,0xA1,0x44,0x03,0x42,0x00
        };
        unsigned char *ptr = seckey;
        memcpy(ptr, begin, sizeof(begin)); ptr += sizeof(begin);
        memcpy(ptr, key32, 32); ptr += 32;
        memcpy(ptr, middle, sizeof(middle)); ptr += sizeof(middle);
        pubkeylen = CPubKey::SIZE;
        secp256k1_ec_pubkey_serialize(ctx, ptr, &pubkeylen, &pubkey, SECP256K1_EC_UNCOMPRESSED);
        ptr += pubkeylen;
        *seckeylen = ptr - seckey;
        assert(*seckeylen == CKey::SIZE);
    }
    return 1;
}

bool CKey::Check(const unsigned char *vch) {
    return secp256k1_ec_seckey_verify(secp256k1_context_sign, vch);
}

void CKey::MakeNewKey(bool fCompressedIn) {
    MakeKeyData();
    do {
        GetStrongRandBytes(*keydata);
    } while (!Check(keydata->data()));
    fCompressed = fCompressedIn;
}

bool CKey::Negate()
{
    assert(keydata);
    return secp256k1_ec_seckey_negate(secp256k1_context_sign, keydata->data());
}

CPrivKey CKey::GetPrivKey() const {
    assert(keydata);
    CPrivKey seckey;
    int ret;
    size_t seckeylen;
    seckey.resize(SIZE);
    seckeylen = SIZE;
    ret = ec_seckey_export_der(secp256k1_context_sign, seckey.data(), &seckeylen, begin(), fCompressed);
    assert(ret);
    seckey.resize(seckeylen);
    return seckey;
}

CPubKey CKey::GetPubKey() const {
    assert(keydata);
    secp256k1_pubkey pubkey;
    size_t clen = CPubKey::SIZE;
    CPubKey result;
    int ret = secp256k1_ec_pubkey_create(secp256k1_context_sign, &pubkey, begin());
    assert(ret);
    secp256k1_ec_pubkey_serialize(secp256k1_context_sign, (unsigned char*)result.begin(), &clen, &pubkey, fCompressed ? SECP256K1_EC_COMPRESSED : SECP256K1_EC_UNCOMPRESSED);
    assert(result.size() == clen);
    assert(result.IsValid());
    return result;
}

// Check that the sig has a low R value and will be less than 71 bytes
bool SigHasLowR(const secp256k1_ecdsa_signature* sig)
{
    unsigned char compact_sig[64];
    secp256k1_ecdsa_signature_serialize_compact(secp256k1_context_sign, compact_sig, sig);

    // In DER serialization, all values are interpreted as big-endian, signed integers. The highest bit in the integer indicates
    // its signed-ness; 0 is positive, 1 is negative. When the value is interpreted as a negative integer, it must be converted
    // to a positive value by prepending a 0x00 byte so that the highest bit is 0. We can avoid this prepending by ensuring that
    // our highest bit is always 0, and thus we must check that the first byte is less than 0x80.
    return compact_sig[0] < 0x80;
}

bool CKey::Sign(const uint256 &hash, std::vector<unsigned char>& vchSig, bool grind, uint32_t test_case) const {
    if (!keydata)
        return false;
    vchSig.resize(CPubKey::SIGNATURE_SIZE);
    size_t nSigLen = CPubKey::SIGNATURE_SIZE;
    unsigned char extra_entropy[32] = {0};
    WriteLE32(extra_entropy, test_case);
    secp256k1_ecdsa_signature sig;
    uint32_t counter = 0;
    int ret = secp256k1_ecdsa_sign(secp256k1_context_sign, &sig, hash.begin(), begin(), secp256k1_nonce_function_rfc6979, (!grind && test_case) ? extra_entropy : nullptr);

    // Grind for low R
    while (ret && !SigHasLowR(&sig) && grind) {
        WriteLE32(extra_entropy, ++counter);
        ret = secp256k1_ecdsa_sign(secp256k1_context_sign, &sig, hash.begin(), begin(), secp256k1_nonce_function_rfc6979, extra_entropy);
    }
    assert(ret);
    secp256k1_ecdsa_signature_serialize_der(secp256k1_context_sign, vchSig.data(), &nSigLen, &sig);
    vchSig.resize(nSigLen);
    // Additional verification step to prevent using a potentially corrupted signature
    secp256k1_pubkey pk;
    ret = secp256k1_ec_pubkey_create(secp256k1_context_sign, &pk, begin());
    assert(ret);
    ret = secp256k1_ecdsa_verify(secp256k1_context_static, &sig, hash.begin(), &pk);
    assert(ret);
    return true;
}

bool CKey::VerifyPubKey(const CPubKey& pubkey) const {
    if (pubkey.IsCompressed() != fCompressed) {
        return false;
    }
    unsigned char rnd[8];
    std::string str = "Bitcoin key verification\n";
    GetRandBytes(rnd);
    uint256 hash{Hash(str, rnd)};
    std::vector<unsigned char> vchSig;
    Sign(hash, vchSig);
    return pubkey.Verify(hash, vchSig);
}

bool CKey::SignCompact(const uint256 &hash, std::vector<unsigned char>& vchSig) const {
    if (!keydata)
        return false;
    vchSig.resize(CPubKey::COMPACT_SIGNATURE_SIZE);
    int rec = -1;
    secp256k1_ecdsa_recoverable_signature rsig;
    int ret = secp256k1_ecdsa_sign_recoverable(secp256k1_context_sign, &rsig, hash.begin(), begin(), secp256k1_nonce_function_rfc6979, nullptr);
    assert(ret);
    ret = secp256k1_ecdsa_recoverable_signature_serialize_compact(secp256k1_context_sign, &vchSig[1], &rec, &rsig);
    assert(ret);
    assert(rec != -1);
    vchSig[0] = 27 + rec + (fCompressed ? 4 : 0);
    // Additional verification step to prevent using a potentially corrupted signature
    secp256k1_pubkey epk, rpk;
    ret = secp256k1_ec_pubkey_create(secp256k1_context_sign, &epk, begin());
    assert(ret);
    ret = secp256k1_ecdsa_recover(secp256k1_context_static, &rpk, &rsig, hash.begin());
    assert(ret);
    ret = secp256k1_ec_pubkey_cmp(secp256k1_context_static, &epk, &rpk);
    assert(ret == 0);
    return true;
}

bool CKey::SignSchnorr(const uint256& hash, Span<unsigned char> sig, const uint256* merkle_root, const uint256& aux) const
{
    assert(sig.size() == 64);
    secp256k1_keypair keypair;
    if (!secp256k1_keypair_create(secp256k1_context_sign, &keypair, begin())) return false;
    if (merkle_root) {
        secp256k1_xonly_pubkey pubkey;
        if (!secp256k1_keypair_xonly_pub(secp256k1_context_sign, &pubkey, nullptr, &keypair)) return false;
        unsigned char pubkey_bytes[32];
        if (!secp256k1_xonly_pubkey_serialize(secp256k1_context_sign, pubkey_bytes, &pubkey)) return false;
        uint256 tweak = XOnlyPubKey(pubkey_bytes).ComputeTapTweakHash(merkle_root->IsNull() ? nullptr : merkle_root);
        if (!secp256k1_keypair_xonly_tweak_add(secp256k1_context_static, &keypair, tweak.data())) return false;
    }
    bool ret = secp256k1_schnorrsig_sign32(secp256k1_context_sign, sig.data(), hash.data(), &keypair, aux.data());
    if (ret) {
        // Additional verification step to prevent using a potentially corrupted signature
        secp256k1_xonly_pubkey pubkey_verify;
        ret = secp256k1_keypair_xonly_pub(secp256k1_context_static, &pubkey_verify, nullptr, &keypair);
        ret &= secp256k1_schnorrsig_verify(secp256k1_context_static, sig.data(), hash.begin(), 32, &pubkey_verify);
    }
    if (!ret) memory_cleanse(sig.data(), sig.size());
    memory_cleanse(&keypair, sizeof(keypair));
    return ret;
}

bool CKey::Load(const CPrivKey &seckey, const CPubKey &vchPubKey, bool fSkipCheck=false) {
    MakeKeyData();
    if (!ec_seckey_import_der(secp256k1_context_sign, (unsigned char*)begin(), seckey.data(), seckey.size())) {
        ClearKeyData();
        return false;
    }
    fCompressed = vchPubKey.IsCompressed();

    if (fSkipCheck)
        return true;

    return VerifyPubKey(vchPubKey);
}

bool CKey::Derive(CKey& keyChild, ChainCode &ccChild, unsigned int nChild, const ChainCode& cc) const {
    assert(IsValid());
    assert(IsCompressed());
    std::vector<unsigned char, secure_allocator<unsigned char>> vout(64);
    if ((nChild >> 31) == 0) {
        CPubKey pubkey = GetPubKey();
        assert(pubkey.size() == CPubKey::COMPRESSED_SIZE);
        BIP32Hash(cc, nChild, *pubkey.begin(), pubkey.begin()+1, vout.data());
    } else {
        assert(size() == 32);
        BIP32Hash(cc, nChild, 0, begin(), vout.data());
    }
    memcpy(ccChild.begin(), vout.data()+32, 32);
    keyChild.Set(begin(), begin() + 32, true);
    bool ret = secp256k1_ec_seckey_tweak_add(secp256k1_context_sign, (unsigned char*)keyChild.begin(), vout.data());
    if (!ret) keyChild.ClearKeyData();
    return ret;
}

EllSwiftPubKey CKey::EllSwiftCreate(Span<const std::byte> ent32) const
{
    assert(keydata);
    assert(ent32.size() == 32);
    std::array<std::byte, EllSwiftPubKey::size()> encoded_pubkey;

    auto success = secp256k1_ellswift_create(secp256k1_context_sign,
                                             UCharCast(encoded_pubkey.data()),
                                             keydata->data(),
                                             UCharCast(ent32.data()));

    // Should always succeed for valid keys (asserted above).
    assert(success);
    return {encoded_pubkey};
}

ECDHSecret CKey::ComputeBIP324ECDHSecret(const EllSwiftPubKey& their_ellswift, const EllSwiftPubKey& our_ellswift, bool initiating) const
{
    assert(keydata);

    ECDHSecret output;
    // BIP324 uses the initiator as party A, and the responder as party B. Remap the inputs
    // accordingly:
    bool success = secp256k1_ellswift_xdh(secp256k1_context_sign,
                                          UCharCast(output.data()),
                                          UCharCast(initiating ? our_ellswift.data() : their_ellswift.data()),
                                          UCharCast(initiating ? their_ellswift.data() : our_ellswift.data()),
                                          keydata->data(),
                                          initiating ? 0 : 1,
                                          secp256k1_ellswift_xdh_hash_function_bip324,
                                          nullptr);
    // Should always succeed for valid keys (assert above).
    assert(success);
    return output;
}

CKey GenerateRandomKey(bool compressed) noexcept
{
    CKey key;
    key.MakeNewKey(/*fCompressed=*/compressed);
    return key;
}

bool CExtKey::Derive(CExtKey &out, unsigned int _nChild) const {
    if (nDepth == std::numeric_limits<unsigned char>::max()) return false;
    out.nDepth = nDepth + 1;
    CKeyID id = key.GetPubKey().GetID();
    memcpy(out.vchFingerprint, &id, 4);
    out.nChild = _nChild;
    return key.Derive(out.key, out.chaincode, _nChild, chaincode);
}

void CExtKey::SetSeed(Span<const std::byte> seed)
{
    static const unsigned char hashkey[] = {'B','i','t','c','o','i','n',' ','s','e','e','d'};
    std::vector<unsigned char, secure_allocator<unsigned char>> vout(64);
    CHMAC_SHA512{hashkey, sizeof(hashkey)}.Write(UCharCast(seed.data()), seed.size()).Finalize(vout.data());
    key.Set(vout.data(), vout.data() + 32, true);
    memcpy(chaincode.begin(), vout.data() + 32, 32);
    nDepth = 0;
    nChild = 0;
    memset(vchFingerprint, 0, sizeof(vchFingerprint));
}

CExtPubKey CExtKey::Neuter() const {
    CExtPubKey ret;
    ret.nDepth = nDepth;
    memcpy(ret.vchFingerprint, vchFingerprint, 4);
    ret.nChild = nChild;
    ret.pubkey = key.GetPubKey();
    ret.chaincode = chaincode;
    return ret;
}

void CExtKey::Encode(unsigned char code[BIP32_EXTKEY_SIZE]) const {
    code[0] = nDepth;
    memcpy(code+1, vchFingerprint, 4);
    WriteBE32(code+5, nChild);
    memcpy(code+9, chaincode.begin(), 32);
    code[41] = 0;
    assert(key.size() == 32);
    memcpy(code+42, key.begin(), 32);
}

void CExtKey::Decode(const unsigned char code[BIP32_EXTKEY_SIZE]) {
    nDepth = code[0];
    memcpy(vchFingerprint, code+1, 4);
    nChild = ReadBE32(code+5);
    memcpy(chaincode.begin(), code+9, 32);
    key.Set(code+42, code+BIP32_EXTKEY_SIZE, true);
    if ((nDepth == 0 && (nChild != 0 || ReadLE32(vchFingerprint) != 0)) || code[41] != 0) key = CKey();
}

bool ECC_InitSanityCheck() {
    CKey key = GenerateRandomKey();
    CPubKey pubkey = key.GetPubKey();
    return key.VerifyPubKey(pubkey);
}

void ECC_Start() {
    assert(secp256k1_context_sign == nullptr);

    secp256k1_context *ctx = secp256k1_context_create(SECP256K1_CONTEXT_NONE);
    assert(ctx != nullptr);

    {
        // Pass in a random blinding seed to the secp256k1 context.
        std::vector<unsigned char, secure_allocator<unsigned char>> vseed(32);
        GetRandBytes(vseed);
        bool ret = secp256k1_context_randomize(ctx, vseed.data());
        assert(ret);
    }

    secp256k1_context_sign = ctx;
}

void ECC_Stop() {
    secp256k1_context *ctx = secp256k1_context_sign;
    secp256k1_context_sign = nullptr;

    if (ctx) {
        secp256k1_context_destroy(ctx);
    }
}