libbitcoinkernel-sys-covenants 0.0.22

Raw Rust bindings to libbitcoinkernel with added covenant op_codes
Documentation 
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

/*************************************************************************
 * Written in 2020-2022 by Elichai Turkel                                *
 * To the extent possible under law, the author(s) have dedicated all    *
 * copyright and related and neighboring rights to the software in this  *
 * file to the public domain worldwide. This software is distributed     *
 * without any warranty. For the CC0 Public Domain Dedication, see       *
 * EXAMPLES_COPYING or https://creativecommons.org/publicdomain/zero/1.0 *
 *************************************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <string.h>

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

#include "examples_util.h"

int main(void) {
    unsigned char msg[] = {'H', 'e', 'l', 'l', 'o', ' ', 'W', 'o', 'r', 'l', 'd', '!'};
    unsigned char msg_hash[32];
    unsigned char tag[] = {'m', 'y', '_', 'f', 'a', 'n', 'c', 'y', '_', 'p', 'r', 'o', 't', 'o', 'c', 'o', 'l'};
    unsigned char seckey[32];
    unsigned char randomize[32];
    unsigned char auxiliary_rand[32];
    unsigned char serialized_pubkey[32];
    unsigned char signature[64];
    int is_signature_valid, is_signature_valid2;
    int return_val;
    secp256k1_xonly_pubkey pubkey;
    secp256k1_keypair keypair;
    /* Before we can call actual API functions, we need to create a "context". */
    secp256k1_context* ctx = secp256k1_context_create(SECP256K1_CONTEXT_NONE);
    if (!fill_random(randomize, sizeof(randomize))) {
        printf("Failed to generate randomness\n");
        return EXIT_FAILURE;
    }
    /* Randomizing the context is recommended to protect against side-channel
     * leakage See `secp256k1_context_randomize` in secp256k1.h for more
     * information about it. This should never fail. */
    return_val = secp256k1_context_randomize(ctx, randomize);
    assert(return_val);

    /*** Key Generation ***/
    if (!fill_random(seckey, sizeof(seckey))) {
        printf("Failed to generate randomness\n");
        return EXIT_FAILURE;
    }
    /* Try to create a keypair with a valid context. This only fails if the
     * secret key is zero or out of range (greater than secp256k1's order). Note
     * that the probability of this occurring is negligible with a properly
     * functioning random number generator. */
    if (!secp256k1_keypair_create(ctx, &keypair, seckey)) {
        printf("Generated secret key is invalid. This indicates an issue with the random number generator.\n");
        return EXIT_FAILURE;
    }

    /* Extract the X-only public key from the keypair. We pass NULL for
     * `pk_parity` as the parity isn't needed for signing or verification.
     * `secp256k1_keypair_xonly_pub` supports returning the parity for
     * other use cases such as tests or verifying Taproot tweaks.
     * This should never fail with a valid context and public key. */
    return_val = secp256k1_keypair_xonly_pub(ctx, &pubkey, NULL, &keypair);
    assert(return_val);

    /* Serialize the public key. Should always return 1 for a valid public key. */
    return_val = secp256k1_xonly_pubkey_serialize(ctx, serialized_pubkey, &pubkey);
    assert(return_val);

    /*** Signing ***/

    /* Instead of signing (possibly very long) messages directly, we sign a
     * 32-byte hash of the message in this example.
     *
     * We use secp256k1_tagged_sha256 to create this hash. This function expects
     * a context-specific "tag", which restricts the context in which the signed
     * messages should be considered valid. For example, if protocol A mandates
     * to use the tag "my_fancy_protocol" and protocol B mandates to use the tag
     * "my_boring_protocol", then signed messages from protocol A will never be
     * valid in protocol B (and vice versa), even if keys are reused across
     * protocols. This implements "domain separation", which is considered good
     * practice. It avoids attacks in which users are tricked into signing a
     * message that has intended consequences in the intended context (e.g.,
     * protocol A) but would have unintended consequences if it were valid in
     * some other context (e.g., protocol B). */
    return_val = secp256k1_tagged_sha256(ctx, msg_hash, tag, sizeof(tag), msg, sizeof(msg));
    assert(return_val);

    /* Generate 32 bytes of randomness to use with BIP-340 schnorr signing. */
    if (!fill_random(auxiliary_rand, sizeof(auxiliary_rand))) {
        printf("Failed to generate randomness\n");
        return EXIT_FAILURE;
    }

    /* Generate a Schnorr signature.
     *
     * We use the secp256k1_schnorrsig_sign32 function that provides a simple
     * interface for signing 32-byte messages (which in our case is a hash of
     * the actual message). BIP-340 recommends passing 32 bytes of randomness
     * to the signing function to improve security against side-channel attacks.
     * Signing with a valid context, a 32-byte message, a verified keypair, and
     * any 32 bytes of auxiliary random data should never fail. */
    return_val = secp256k1_schnorrsig_sign32(ctx, signature, msg_hash, &keypair, auxiliary_rand);
    assert(return_val);

    /*** Verification ***/

    /* Deserialize the public key. This will return 0 if the public key can't
     * be parsed correctly */
    if (!secp256k1_xonly_pubkey_parse(ctx, &pubkey, serialized_pubkey)) {
        printf("Failed parsing the public key\n");
        return EXIT_FAILURE;
    }

    /* Compute the tagged hash on the received messages using the same tag as the signer. */
    return_val = secp256k1_tagged_sha256(ctx, msg_hash, tag, sizeof(tag), msg, sizeof(msg));
    assert(return_val);

    /* Verify a signature. This will return 1 if it's valid and 0 if it's not. */
    is_signature_valid = secp256k1_schnorrsig_verify(ctx, signature, msg_hash, 32, &pubkey);


    printf("Is the signature valid? %s\n", is_signature_valid ? "true" : "false");
    printf("Secret Key: ");
    print_hex(seckey, sizeof(seckey));
    printf("Public Key: ");
    print_hex(serialized_pubkey, sizeof(serialized_pubkey));
    printf("Signature: ");
    print_hex(signature, sizeof(signature));

    /* This will clear everything from the context and free the memory */
    secp256k1_context_destroy(ctx);

    /* Bonus example: if all we need is signature verification (and no key
       generation or signing), we don't need to use a context created via
       secp256k1_context_create(). We can simply use the static (i.e., global)
       context secp256k1_context_static. See its description in
       include/secp256k1.h for details. */
    is_signature_valid2 = secp256k1_schnorrsig_verify(secp256k1_context_static,
                                                      signature, msg_hash, 32, &pubkey);
    assert(is_signature_valid2 == is_signature_valid);

    /* It's best practice to try to clear secrets from memory after using them.
     * This is done because some bugs can allow an attacker to leak memory, for
     * example through "out of bounds" array access (see Heartbleed), or the OS
     * swapping them to disk. Hence, we overwrite the secret key buffer with zeros.
     *
     * Here we are preventing these writes from being optimized out, as any good compiler
     * will remove any writes that aren't used. */
    secure_erase(seckey, sizeof(seckey));
    return EXIT_SUCCESS;
}