frost/secp256k1-zkp
3
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

schnorrsig: Adapt example to new API

Browse Source
This commit is contained in:
Tim Ruffing 2022-03-16 12:40:08 +01:00
parent 99e6568fc6
commit f813bb0df3
1 changed files with 32 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

48
examples/schnorr.c
View File

@ -18,16 +18,9 @@
#include "random.h"
int main(void) {
/* Instead of signing the message directly, we must sign a 32-byte hash.
* Here the message is "Hello, world!" and the hash function was SHA-256.
* An actual implementation should just call SHA-256, but this example
* hardcodes the output to avoid depending on an additional library. */
unsigned char msg_hash[32] = {
0x31, 0x5F, 0x5B, 0xDB, 0x76, 0xD0, 0x78, 0xC4,
0x3B, 0x8A, 0xC0, 0x06, 0x4E, 0x4A, 0x01, 0x64,
0x61, 0x2B, 0x1F, 0xCE, 0x77, 0xC8, 0x69, 0x34,
0x5B, 0xFC, 0x94, 0xC7, 0x58, 0x94, 0xED, 0xD3,
};
unsigned char msg[12] = "Hello World!";
unsigned char msg_hash[32];
unsigned char tag[17] = "my_fancy_protocol";
unsigned char seckey[32];
unsigned char randomize[32];
unsigned char auxiliary_rand[32];
@ -84,18 +77,37 @@ int main(void) {
/*** 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 1;
}
/* Generate a Schnorr signature `noncefp` and `ndata` allows you to pass a
* custom nonce function, passing `NULL` will use the BIP-340 safe default.
* BIP-340 recommends passing 32 bytes of randomness to the nonce function to
* improve security against side-channel attacks. Signing with a valid
* context, verified keypair and the default nonce function should never
* fail. */
/* 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);
@ -108,6 +120,10 @@ int main(void) {
return 1;
}
/* 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);