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Merge bitcoin-core/secp256k1#1825: hash: remove redundant secp256k1_sha256_initialize in tagged hash midstate functions

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f48b1bfa5d hash: add midstate initializer and use it for tagged hashes (w0xlt)

Pull request description:

  Each tagged hash midstate function (e.g., `secp256k1_schnorrsig_sha256_tagged`) calls `secp256k1_sha256_initialize` before immediately overwriting every field it sets: `s[0]` through `s[7]` and `bytes`. The `buf[64]` member does not need initialization either, because `bytes` is set to 64, which means the buffer position (`bytes & 0x3F`) (`= bytes % 64`) is 0, so buf is always written before being read.

  Remove the 11 redundant `secp256k1_sha256_initialize` calls across the `schnorrsig`, `ellswift`, and `musig` modules.

ACKs for top commit:
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    utACK f48b1bfa5d
  theStack:
    Code-review ACK f48b1bfa5d

Tree-SHA512: 769beb96f3921cc3c180ed0d17484ffa0dc78041c889a8e56603679d8eaca5fe13e63759ada78f83d8e0ff7aae392e6bcbc1a9fe8b959105ea4a3d8ef51abf15
This commit is contained in:
merge-script
2026-02-27 21:10:43 +01:00
parent 3019186a6d f48b1bfa5d
commit 95e6815843
7 changed files with 80 additions and 118 deletions
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47
src/modules/schnorrsig/main_impl.h
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@@ -14,33 +14,21 @@
/* Initializes SHA256 with fixed midstate. This midstate was computed by applying
* SHA256 to SHA256("BIP0340/nonce")||SHA256("BIP0340/nonce"). */
static void secp256k1_nonce_function_bip340_sha256_tagged(secp256k1_sha256 *sha) {
secp256k1_sha256_initialize(sha);
sha->s[0] = 0x46615b35ul;
sha->s[1] = 0xf4bfbff7ul;
sha->s[2] = 0x9f8dc671ul;
sha->s[3] = 0x83627ab3ul;
sha->s[4] = 0x60217180ul;
sha->s[5] = 0x57358661ul;
sha->s[6] = 0x21a29e54ul;
sha->s[7] = 0x68b07b4cul;
sha->bytes = 64;
static const uint32_t midstate[8] = {
0x46615b35ul, 0xf4bfbff7ul, 0x9f8dc671ul, 0x83627ab3ul,
0x60217180ul, 0x57358661ul, 0x21a29e54ul, 0x68b07b4cul
};
secp256k1_sha256_initialize_midstate(sha, 64, midstate);
}
/* Initializes SHA256 with fixed midstate. This midstate was computed by applying
* SHA256 to SHA256("BIP0340/aux")||SHA256("BIP0340/aux"). */
static void secp256k1_nonce_function_bip340_sha256_tagged_aux(secp256k1_sha256 *sha) {
secp256k1_sha256_initialize(sha);
sha->s[0] = 0x24dd3219ul;
sha->s[1] = 0x4eba7e70ul;
sha->s[2] = 0xca0fabb9ul;
sha->s[3] = 0x0fa3166dul;
sha->s[4] = 0x3afbe4b1ul;
sha->s[5] = 0x4c44df97ul;
sha->s[6] = 0x4aac2739ul;
sha->s[7] = 0x249e850aul;
sha->bytes = 64;
static const uint32_t midstate[8] = {
0x24dd3219ul, 0x4eba7e70ul, 0xca0fabb9ul, 0x0fa3166dul,
0x3afbe4b1ul, 0x4c44df97ul, 0x4aac2739ul, 0x249e850aul
};
secp256k1_sha256_initialize_midstate(sha, 64, midstate);
}
/* algo argument for nonce_function_bip340 to derive the nonce exactly as stated in BIP-340
@@ -104,16 +92,11 @@ const secp256k1_nonce_function_hardened secp256k1_nonce_function_bip340 = nonce_
/* Initializes SHA256 with fixed midstate. This midstate was computed by applying
* SHA256 to SHA256("BIP0340/challenge")||SHA256("BIP0340/challenge"). */
static void secp256k1_schnorrsig_sha256_tagged(secp256k1_sha256 *sha) {
secp256k1_sha256_initialize(sha);
sha->s[0] = 0x9cecba11ul;
sha->s[1] = 0x23925381ul;
sha->s[2] = 0x11679112ul;
sha->s[3] = 0xd1627e0ful;
sha->s[4] = 0x97c87550ul;
sha->s[5] = 0x003cc765ul;
sha->s[6] = 0x90f61164ul;
sha->s[7] = 0x33e9b66aul;
sha->bytes = 64;
static const uint32_t midstate[8] = {
0x9cecba11ul, 0x23925381ul, 0x11679112ul, 0xd1627e0ful,
0x97c87550ul, 0x003cc765ul, 0x90f61164ul, 0x33e9b66aul
};
secp256k1_sha256_initialize_midstate(sha, 64, midstate);
}
static void secp256k1_schnorrsig_challenge(secp256k1_scalar* e, const unsigned char *r32, const unsigned char *msg, size_t msglen, const unsigned char *pubkey32)