hash_impl.h

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/***********************************************************************
 * Copyright (c) 2014 Pieter Wuille                                    *
 * Distributed under the MIT software license, see the accompanying    *
 * file COPYING or https://www.opensource.org/licenses/mit-license.php.*
 ***********************************************************************/
 
#ifndef SECP256K1_HASH_IMPL_H
#define SECP256K1_HASH_IMPL_H
 
#include "hash.h"
#include "util.h"
 
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
 
#define Ch(x,y,z) ((z) ^ ((x) & ((y) ^ (z))))
#define Maj(x,y,z) (((x) & (y)) | ((z) & ((x) | (y))))
#define Sigma0(x) (((x) >> 2 | (x) << 30) ^ ((x) >> 13 | (x) << 19) ^ ((x) >> 22 | (x) << 10))
#define Sigma1(x) (((x) >> 6 | (x) << 26) ^ ((x) >> 11 | (x) << 21) ^ ((x) >> 25 | (x) << 7))
#define sigma0(x) (((x) >> 7 | (x) << 25) ^ ((x) >> 18 | (x) << 14) ^ ((x) >> 3))
#define sigma1(x) (((x) >> 17 | (x) << 15) ^ ((x) >> 19 | (x) << 13) ^ ((x) >> 10))
 
#define Round(a,b,c,d,e,f,g,h,k,w) do { \
    uint32_t t1 = (h) + Sigma1(e) + Ch((e), (f), (g)) + (k) + (w); \
    uint32_t t2 = Sigma0(a) + Maj((a), (b), (c)); \
    (d) += t1; \
    (h) = t1 + t2; \
} while(0)
 
static void secp256k1_sha256_initialize(secp256k1_sha256 *hash) {
    hash->s[0] = 0x6a09e667ul;
    hash->s[1] = 0xbb67ae85ul;
    hash->s[2] = 0x3c6ef372ul;
    hash->s[3] = 0xa54ff53aul;
    hash->s[4] = 0x510e527ful;
    hash->s[5] = 0x9b05688cul;
    hash->s[6] = 0x1f83d9abul;
    hash->s[7] = 0x5be0cd19ul;
    hash->bytes = 0;
}
 
static void secp256k1_sha256_initialize_midstate(secp256k1_sha256 *hash, uint64_t bytes, const uint32_t state[8]) {
    VERIFY_CHECK((bytes & 0x3F) == 0);
    VERIFY_CHECK(state != NULL);
    memcpy(hash->s, state, sizeof(hash->s));
    hash->bytes = bytes;
}

static void secp256k1_sha256_transform_impl(uint32_t* s, const unsigned char* buf) {
    uint32_t a = s[0], b = s[1], c = s[2], d = s[3], e = s[4], f = s[5], g = s[6], h = s[7];
    uint32_t w0, w1, w2, w3, w4, w5, w6, w7, w8, w9, w10, w11, w12, w13, w14, w15;
 
    Round(a, b, c, d, e, f, g, h, 0x428a2f98,  w0 = secp256k1_read_be32(&buf[0]));
    Round(h, a, b, c, d, e, f, g, 0x71374491,  w1 = secp256k1_read_be32(&buf[4]));
    Round(g, h, a, b, c, d, e, f, 0xb5c0fbcf,  w2 = secp256k1_read_be32(&buf[8]));
    Round(f, g, h, a, b, c, d, e, 0xe9b5dba5,  w3 = secp256k1_read_be32(&buf[12]));
    Round(e, f, g, h, a, b, c, d, 0x3956c25b,  w4 = secp256k1_read_be32(&buf[16]));
    Round(d, e, f, g, h, a, b, c, 0x59f111f1,  w5 = secp256k1_read_be32(&buf[20]));
    Round(c, d, e, f, g, h, a, b, 0x923f82a4,  w6 = secp256k1_read_be32(&buf[24]));
    Round(b, c, d, e, f, g, h, a, 0xab1c5ed5,  w7 = secp256k1_read_be32(&buf[28]));
    Round(a, b, c, d, e, f, g, h, 0xd807aa98,  w8 = secp256k1_read_be32(&buf[32]));
    Round(h, a, b, c, d, e, f, g, 0x12835b01,  w9 = secp256k1_read_be32(&buf[36]));
    Round(g, h, a, b, c, d, e, f, 0x243185be, w10 = secp256k1_read_be32(&buf[40]));
    Round(f, g, h, a, b, c, d, e, 0x550c7dc3, w11 = secp256k1_read_be32(&buf[44]));
    Round(e, f, g, h, a, b, c, d, 0x72be5d74, w12 = secp256k1_read_be32(&buf[48]));
    Round(d, e, f, g, h, a, b, c, 0x80deb1fe, w13 = secp256k1_read_be32(&buf[52]));
    Round(c, d, e, f, g, h, a, b, 0x9bdc06a7, w14 = secp256k1_read_be32(&buf[56]));
    Round(b, c, d, e, f, g, h, a, 0xc19bf174, w15 = secp256k1_read_be32(&buf[60]));
 
    Round(a, b, c, d, e, f, g, h, 0xe49b69c1, w0 += sigma1(w14) + w9 + sigma0(w1));
    Round(h, a, b, c, d, e, f, g, 0xefbe4786, w1 += sigma1(w15) + w10 + sigma0(w2));
    Round(g, h, a, b, c, d, e, f, 0x0fc19dc6, w2 += sigma1(w0) + w11 + sigma0(w3));
    Round(f, g, h, a, b, c, d, e, 0x240ca1cc, w3 += sigma1(w1) + w12 + sigma0(w4));
    Round(e, f, g, h, a, b, c, d, 0x2de92c6f, w4 += sigma1(w2) + w13 + sigma0(w5));
    Round(d, e, f, g, h, a, b, c, 0x4a7484aa, w5 += sigma1(w3) + w14 + sigma0(w6));
    Round(c, d, e, f, g, h, a, b, 0x5cb0a9dc, w6 += sigma1(w4) + w15 + sigma0(w7));
    Round(b, c, d, e, f, g, h, a, 0x76f988da, w7 += sigma1(w5) + w0 + sigma0(w8));
    Round(a, b, c, d, e, f, g, h, 0x983e5152, w8 += sigma1(w6) + w1 + sigma0(w9));
    Round(h, a, b, c, d, e, f, g, 0xa831c66d, w9 += sigma1(w7) + w2 + sigma0(w10));
    Round(g, h, a, b, c, d, e, f, 0xb00327c8, w10 += sigma1(w8) + w3 + sigma0(w11));
    Round(f, g, h, a, b, c, d, e, 0xbf597fc7, w11 += sigma1(w9) + w4 + sigma0(w12));
    Round(e, f, g, h, a, b, c, d, 0xc6e00bf3, w12 += sigma1(w10) + w5 + sigma0(w13));
    Round(d, e, f, g, h, a, b, c, 0xd5a79147, w13 += sigma1(w11) + w6 + sigma0(w14));
    Round(c, d, e, f, g, h, a, b, 0x06ca6351, w14 += sigma1(w12) + w7 + sigma0(w15));
    Round(b, c, d, e, f, g, h, a, 0x14292967, w15 += sigma1(w13) + w8 + sigma0(w0));
 
    Round(a, b, c, d, e, f, g, h, 0x27b70a85, w0 += sigma1(w14) + w9 + sigma0(w1));
    Round(h, a, b, c, d, e, f, g, 0x2e1b2138, w1 += sigma1(w15) + w10 + sigma0(w2));
    Round(g, h, a, b, c, d, e, f, 0x4d2c6dfc, w2 += sigma1(w0) + w11 + sigma0(w3));
    Round(f, g, h, a, b, c, d, e, 0x53380d13, w3 += sigma1(w1) + w12 + sigma0(w4));
    Round(e, f, g, h, a, b, c, d, 0x650a7354, w4 += sigma1(w2) + w13 + sigma0(w5));
    Round(d, e, f, g, h, a, b, c, 0x766a0abb, w5 += sigma1(w3) + w14 + sigma0(w6));
    Round(c, d, e, f, g, h, a, b, 0x81c2c92e, w6 += sigma1(w4) + w15 + sigma0(w7));
    Round(b, c, d, e, f, g, h, a, 0x92722c85, w7 += sigma1(w5) + w0 + sigma0(w8));
    Round(a, b, c, d, e, f, g, h, 0xa2bfe8a1, w8 += sigma1(w6) + w1 + sigma0(w9));
    Round(h, a, b, c, d, e, f, g, 0xa81a664b, w9 += sigma1(w7) + w2 + sigma0(w10));
    Round(g, h, a, b, c, d, e, f, 0xc24b8b70, w10 += sigma1(w8) + w3 + sigma0(w11));
    Round(f, g, h, a, b, c, d, e, 0xc76c51a3, w11 += sigma1(w9) + w4 + sigma0(w12));
    Round(e, f, g, h, a, b, c, d, 0xd192e819, w12 += sigma1(w10) + w5 + sigma0(w13));
    Round(d, e, f, g, h, a, b, c, 0xd6990624, w13 += sigma1(w11) + w6 + sigma0(w14));
    Round(c, d, e, f, g, h, a, b, 0xf40e3585, w14 += sigma1(w12) + w7 + sigma0(w15));
    Round(b, c, d, e, f, g, h, a, 0x106aa070, w15 += sigma1(w13) + w8 + sigma0(w0));
 
    Round(a, b, c, d, e, f, g, h, 0x19a4c116, w0 += sigma1(w14) + w9 + sigma0(w1));
    Round(h, a, b, c, d, e, f, g, 0x1e376c08, w1 += sigma1(w15) + w10 + sigma0(w2));
    Round(g, h, a, b, c, d, e, f, 0x2748774c, w2 += sigma1(w0) + w11 + sigma0(w3));
    Round(f, g, h, a, b, c, d, e, 0x34b0bcb5, w3 += sigma1(w1) + w12 + sigma0(w4));
    Round(e, f, g, h, a, b, c, d, 0x391c0cb3, w4 += sigma1(w2) + w13 + sigma0(w5));
    Round(d, e, f, g, h, a, b, c, 0x4ed8aa4a, w5 += sigma1(w3) + w14 + sigma0(w6));
    Round(c, d, e, f, g, h, a, b, 0x5b9cca4f, w6 += sigma1(w4) + w15 + sigma0(w7));
    Round(b, c, d, e, f, g, h, a, 0x682e6ff3, w7 += sigma1(w5) + w0 + sigma0(w8));
    Round(a, b, c, d, e, f, g, h, 0x748f82ee, w8 += sigma1(w6) + w1 + sigma0(w9));
    Round(h, a, b, c, d, e, f, g, 0x78a5636f, w9 += sigma1(w7) + w2 + sigma0(w10));
    Round(g, h, a, b, c, d, e, f, 0x84c87814, w10 += sigma1(w8) + w3 + sigma0(w11));
    Round(f, g, h, a, b, c, d, e, 0x8cc70208, w11 += sigma1(w9) + w4 + sigma0(w12));
    Round(e, f, g, h, a, b, c, d, 0x90befffa, w12 += sigma1(w10) + w5 + sigma0(w13));
    Round(d, e, f, g, h, a, b, c, 0xa4506ceb, w13 += sigma1(w11) + w6 + sigma0(w14));
    Round(c, d, e, f, g, h, a, b, 0xbef9a3f7, w14 + sigma1(w12) + w7 + sigma0(w15));
    Round(b, c, d, e, f, g, h, a, 0xc67178f2, w15 + sigma1(w13) + w8 + sigma0(w0));
 
    s[0] += a;
    s[1] += b;
    s[2] += c;
    s[3] += d;
    s[4] += e;
    s[5] += f;
    s[6] += g;
    s[7] += h;
}
 
static void secp256k1_sha256_transform(uint32_t *state, const unsigned char *blocks64, size_t n_blocks) {
    while (n_blocks--) {
        secp256k1_sha256_transform_impl(state, blocks64);
        blocks64 += 64;
    }
}
 
/* Perform a smoke test on a supplied SHA256 compression function. */
static int secp256k1_sha256_smoke_test(const secp256k1_sha256_compression_function fn_compression) {
    secp256k1_hash_ctx ctx;
    secp256k1_sha256 sha_msg, sha_accum;
    unsigned char out[32];
    size_t i, j;
 
    /* SHA256 works on 64 byte blocks, secp256k1_sha256_write gives as many blocks
     * at once to compression, so the count is what varies here. A SIMD implementation
     * typically hashes four or eight at a time, then any left over one by one.
     * These lengths cover every number from 1 to 9, which includes counts that
     * divide evenly and counts leaving one, two or three over. */
    static const size_t msg_lens[] = {
        0, 1, 28,               /* Shorter than a block, so padding makes up the rest */
        55, 56,                 /* Final 0x80 and 8 byte length fit in the last block, and don't */
        64, 128, 192, 256, 320, /* 1 to 5 blocks */
        384, 448, 512, 576      /* 6 to 9 blocks */
    };
    unsigned char msg[640]; /* Longest message, plus 64 for the shifted start */
 
    /* Accumulated digest of every message, hashed with the built-in secp256k1_sha256_transform.
     * Note: To regenerate set 'ctx.fn_sha256_compression = secp256k1_sha256_transform' below
     * and print the sha_accum digest. */
    static const unsigned char accum_expected[32] = {
        0x22, 0x8E, 0x6A, 0x1F, 0x78, 0x02, 0x1B, 0xCF,
        0x4E, 0xF4, 0xEA, 0xB3, 0x8A, 0x40, 0x69, 0xBF,
        0x8D, 0xF3, 0x72, 0xAB, 0xE2, 0x11, 0x93, 0xA6,
        0xE6, 0x46, 0x98, 0xBF, 0xD4, 0x3D, 0x19, 0x84,
    };
    /* The purpose of this VERIFY_CHECK is to make anyone aware that they
     * should also change the size of msg_buf when changing the length of the
     * longest message. */
    VERIFY_CHECK(msg_lens[ARRAY_SIZE(msg_lens) - 1] == 576);
 
    VERIFY_CHECK(fn_compression != NULL);
    secp256k1_hash_ctx_init(&ctx);
    ctx.fn_sha256_compression = fn_compression;
    secp256k1_sha256_initialize(&sha_accum);
 
    /* No two blocks of a message are equal, so a function that doesn't advance the block
     * pointer gives a different digest. 251 is prime, so its repeats only line up with
     * block starts every 251 blocks; wrapping at 256 would do so every 4. */
    for (i = 0; i < sizeof(msg); i++) {
        msg[i] = (unsigned char)(i % 251);
    }
 
    /* Each round starts one byte further along to check different alignments,
     * secp256k1_sha256_write invokes compression directly on input >= 64 bytes */
    for (i = 0; i < 64; i++) {
        unsigned char *m = msg + i;
        m[0] ^= 0xff; /* Changes the first byte, so every state after it changes too */
        for (j = 0; j < ARRAY_SIZE(msg_lens); j++) {
            secp256k1_sha256_initialize(&sha_msg);
            secp256k1_sha256_write(&ctx, &sha_msg, m, msg_lens[j]);
            secp256k1_sha256_finalize(&ctx, &sha_msg, out);
            secp256k1_sha256_write(&ctx, &sha_accum, out, 32);
        }
        m[0] ^= 0xff; /* Reset first byte */
    }
 
    /* Compare against pre-computed accumulated digest */
    secp256k1_sha256_finalize(&ctx, &sha_accum, out);
    return secp256k1_memcmp_var(accum_expected, out, 32) == 0;
}
 
static void secp256k1_hash_ctx_init(secp256k1_hash_ctx *hash_ctx) {
    VERIFY_CHECK(hash_ctx != NULL);
    hash_ctx->fn_sha256_compression = secp256k1_sha256_transform;
}
 
static void secp256k1_sha256_write(const secp256k1_hash_ctx *hash_ctx, secp256k1_sha256 *hash, const unsigned char *data, size_t len) {
    size_t chunk_len;
    size_t bufsize = hash->bytes & 0x3F;
    hash->bytes += len;
    VERIFY_CHECK(hash->bytes >= len);
    VERIFY_CHECK(hash_ctx != NULL);
    VERIFY_CHECK(hash_ctx->fn_sha256_compression != NULL);
 
    /* If we exceed the 64-byte block size with this input, process it and wipe the buffer */
    chunk_len = 64 - bufsize;
    if (bufsize && len >= chunk_len) {
        memcpy(hash->buf + bufsize, data, chunk_len);
        data += chunk_len;
        len -= chunk_len;
        hash_ctx->fn_sha256_compression(hash->s, hash->buf, 1);
        bufsize = 0;
    }
 
    /* If we still have data to process, invoke compression directly on the input */
    if (len >= 64) {
        const size_t n_blocks = len / 64;
        const size_t advance = n_blocks * 64;
        hash_ctx->fn_sha256_compression(hash->s, data, n_blocks);
        data += advance;
        len -= advance;
    }
 
    /* Fill the buffer with what remains */
    if (len) {
        memcpy(hash->buf + bufsize, data, len);
    }
}
 
static void secp256k1_sha256_finalize(const secp256k1_hash_ctx *hash_ctx, secp256k1_sha256 *hash, unsigned char *out32) {
    static const unsigned char pad[64] = {0x80};
    unsigned char sizedesc[8];
    int i;
    /* The maximum message size of SHA256 is 2^64-1 bits. */
    VERIFY_CHECK(hash->bytes < ((uint64_t)1 << 61));
    secp256k1_write_be32(&sizedesc[0], hash->bytes >> 29);
    secp256k1_write_be32(&sizedesc[4], hash->bytes << 3);
    secp256k1_sha256_write(hash_ctx, hash, pad, 1 + ((119 - (hash->bytes % 64)) % 64));
    secp256k1_sha256_write(hash_ctx, hash, sizedesc, 8);
    for (i = 0; i < 8; i++) {
        secp256k1_write_be32(&out32[4*i], hash->s[i]);
        hash->s[i] = 0;
    }
}
 
/* Initializes a sha256 struct and writes the 64 byte string
 * SHA256(tag)||SHA256(tag) into it. */
static void secp256k1_sha256_initialize_tagged(const secp256k1_hash_ctx *hash_ctx, secp256k1_sha256 *hash, const unsigned char *tag, size_t taglen) {
    unsigned char buf[32];
    secp256k1_sha256_initialize(hash);
    secp256k1_sha256_write(hash_ctx, hash, tag, taglen);
    secp256k1_sha256_finalize(hash_ctx, hash, buf);
 
    secp256k1_sha256_initialize(hash);
    secp256k1_sha256_write(hash_ctx, hash, buf, 32);
    secp256k1_sha256_write(hash_ctx, hash, buf, 32);
}
 
static void secp256k1_sha256_clear(secp256k1_sha256 *hash) {
    secp256k1_memclear_explicit(hash, sizeof(*hash));
}
 
static void secp256k1_hmac_sha256_initialize(const secp256k1_hash_ctx *hash_ctx, secp256k1_hmac_sha256 *hash, const unsigned char *key, size_t keylen) {
    size_t n;
    unsigned char rkey[64];
    if (keylen <= sizeof(rkey)) {
        memcpy(rkey, key, keylen);
        memset(rkey + keylen, 0, sizeof(rkey) - keylen);
    } else {
        secp256k1_sha256 sha256;
        secp256k1_sha256_initialize(&sha256);
        secp256k1_sha256_write(hash_ctx, &sha256, key, keylen);
        secp256k1_sha256_finalize(hash_ctx, &sha256, rkey);
        memset(rkey + 32, 0, 32);
    }
 
    secp256k1_sha256_initialize(&hash->outer);
    for (n = 0; n < sizeof(rkey); n++) {
        rkey[n] ^= 0x5c;
    }
    secp256k1_sha256_write(hash_ctx, &hash->outer, rkey, sizeof(rkey));
 
    secp256k1_sha256_initialize(&hash->inner);
    for (n = 0; n < sizeof(rkey); n++) {
        rkey[n] ^= 0x5c ^ 0x36;
    }
    secp256k1_sha256_write(hash_ctx, &hash->inner, rkey, sizeof(rkey));
    secp256k1_memclear_explicit(rkey, sizeof(rkey));
}
 
static void secp256k1_hmac_sha256_write(const secp256k1_hash_ctx *hash_ctx, secp256k1_hmac_sha256 *hash, const unsigned char *data, size_t size) {
    secp256k1_sha256_write(hash_ctx, &hash->inner, data, size);
}
 
static void secp256k1_hmac_sha256_finalize(const secp256k1_hash_ctx *hash_ctx, secp256k1_hmac_sha256 *hash, unsigned char *out32) {
    unsigned char temp[32];
    secp256k1_sha256_finalize(hash_ctx, &hash->inner, temp);
    secp256k1_sha256_write(hash_ctx, &hash->outer, temp, 32);
    secp256k1_memclear_explicit(temp, sizeof(temp));
    secp256k1_sha256_finalize(hash_ctx, &hash->outer, out32);
}
 
static void secp256k1_hmac_sha256_clear(secp256k1_hmac_sha256 *hash) {
    secp256k1_memclear_explicit(hash, sizeof(*hash));
}
 
static void secp256k1_rfc6979_hmac_sha256_initialize(const secp256k1_hash_ctx *hash_ctx, secp256k1_rfc6979_hmac_sha256 *rng, const unsigned char *key, size_t keylen) {
    secp256k1_hmac_sha256 hmac;
    static const unsigned char zero[1] = {0x00};
    static const unsigned char one[1] = {0x01};
 
    memset(rng->v, 0x01, 32); /* RFC6979 3.2.b. */
    memset(rng->k, 0x00, 32); /* RFC6979 3.2.c. */
 
    /* RFC6979 3.2.d. */
    secp256k1_hmac_sha256_initialize(hash_ctx, &hmac, rng->k, 32);
    secp256k1_hmac_sha256_write(hash_ctx, &hmac, rng->v, 32);
    secp256k1_hmac_sha256_write(hash_ctx, &hmac, zero, 1);
    secp256k1_hmac_sha256_write(hash_ctx, &hmac, key, keylen);
    secp256k1_hmac_sha256_finalize(hash_ctx, &hmac, rng->k);
    secp256k1_hmac_sha256_initialize(hash_ctx, &hmac, rng->k, 32);
    secp256k1_hmac_sha256_write(hash_ctx, &hmac, rng->v, 32);
    secp256k1_hmac_sha256_finalize(hash_ctx, &hmac, rng->v);
 
    /* RFC6979 3.2.f. */
    secp256k1_hmac_sha256_initialize(hash_ctx, &hmac, rng->k, 32);
    secp256k1_hmac_sha256_write(hash_ctx, &hmac, rng->v, 32);
    secp256k1_hmac_sha256_write(hash_ctx, &hmac, one, 1);
    secp256k1_hmac_sha256_write(hash_ctx, &hmac, key, keylen);
    secp256k1_hmac_sha256_finalize(hash_ctx, &hmac, rng->k);
    secp256k1_hmac_sha256_initialize(hash_ctx, &hmac, rng->k, 32);
    secp256k1_hmac_sha256_write(hash_ctx, &hmac, rng->v, 32);
    secp256k1_hmac_sha256_finalize(hash_ctx, &hmac, rng->v);
    rng->retry = 0;
}
 
static void secp256k1_rfc6979_hmac_sha256_generate(const secp256k1_hash_ctx *hash_ctx, secp256k1_rfc6979_hmac_sha256 *rng, unsigned char *out, size_t outlen) {
    /* RFC6979 3.2.h. */
    static const unsigned char zero[1] = {0x00};
    if (rng->retry) {
        secp256k1_hmac_sha256 hmac;
        secp256k1_hmac_sha256_initialize(hash_ctx, &hmac, rng->k, 32);
        secp256k1_hmac_sha256_write(hash_ctx, &hmac, rng->v, 32);
        secp256k1_hmac_sha256_write(hash_ctx, &hmac, zero, 1);
        secp256k1_hmac_sha256_finalize(hash_ctx, &hmac, rng->k);
        secp256k1_hmac_sha256_initialize(hash_ctx, &hmac, rng->k, 32);
        secp256k1_hmac_sha256_write(hash_ctx, &hmac, rng->v, 32);
        secp256k1_hmac_sha256_finalize(hash_ctx, &hmac, rng->v);
    }
 
    while (outlen > 0) {
        secp256k1_hmac_sha256 hmac;
        size_t now = outlen;
        secp256k1_hmac_sha256_initialize(hash_ctx, &hmac, rng->k, 32);
        secp256k1_hmac_sha256_write(hash_ctx, &hmac, rng->v, 32);
        secp256k1_hmac_sha256_finalize(hash_ctx, &hmac, rng->v);
        if (now > 32) {
            now = 32;
        }
        memcpy(out, rng->v, now);
        out += now;
        outlen -= now;
    }
 
    rng->retry = 1;
}
 
static void secp256k1_rfc6979_hmac_sha256_finalize(secp256k1_rfc6979_hmac_sha256 *rng) {
    (void) rng;
}
 
static void secp256k1_rfc6979_hmac_sha256_clear(secp256k1_rfc6979_hmac_sha256 *rng) {
    secp256k1_memclear_explicit(rng, sizeof(*rng));
}
 
#undef Round
#undef sigma1
#undef sigma0
#undef Sigma1
#undef Sigma0
#undef Maj
#undef Ch
 
#endif /* SECP256K1_HASH_IMPL_H */