1/* $OpenBSD: hkdf.h,v 1.3 2023/08/11 04:52:08 tb Exp $ */
2/* Copyright (c) 2014, Google Inc.
3 *
4 * Permission to use, copy, modify, and/or distribute this software for any
5 * purpose with or without fee is hereby granted, provided that the above
6 * copyright notice and this permission notice appear in all copies.
7 *
8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
11 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
13 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
14 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
15
16#ifndef OPENSSL_HEADER_HKDF_H
17#define OPENSSL_HEADER_HKDF_H
18
19#include <openssl/evp.h>
20
21#if defined(__cplusplus)
22extern "C" {
23#endif
24
25/*
26 * HKDF computes HKDF (as specified by RFC 5869) of initial keying
27 * material |secret| with |salt| and |info| using |digest|, and
28 * outputs |out_len| bytes to |out_key|. It returns one on success and
29 * zero on error.
30 *
31 * HKDF is an Extract-and-Expand algorithm. It does not do any key
32 * stretching, and as such, is not suited to be used alone to generate
33 * a key from a password.
34 */
35
36int HKDF(uint8_t *out_key, size_t out_len, const EVP_MD *digest,
37    const uint8_t *secret, size_t secret_len, const uint8_t *salt,
38    size_t salt_len, const uint8_t *info, size_t info_len);
39
40/*
41 * HKDF_extract computes a HKDF PRK (as specified by RFC 5869) from
42 * initial keying material |secret| and salt |salt| using |digest|,
43 * and outputs |out_len| bytes to |out_key|. The maximum output size
44 * is |EVP_MAX_MD_SIZE|.  It returns one on success and zero on error.
45 */
46int HKDF_extract(uint8_t *out_key, size_t *out_len, const EVP_MD *digest,
47    const uint8_t *secret, size_t secret_len,
48    const uint8_t *salt, size_t salt_len);
49
50/*
51 * HKDF_expand computes a HKDF OKM (as specified by RFC 5869) of
52 * length |out_len| from the PRK |prk| and info |info| using |digest|,
53 * and outputs the result to |out_key|. It returns one on success and
54 * zero on error.
55 */
56int HKDF_expand(uint8_t *out_key, size_t out_len,
57    const EVP_MD *digest, const uint8_t *prk, size_t prk_len,
58    const uint8_t *info,  size_t info_len);
59
60
61#if defined(__cplusplus)
62}  /* extern C */
63#endif
64
65#endif  /* OPENSSL_HEADER_HKDF_H */
66