/* Copyright (c) 2014, Google Inc.
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */

#ifndef OPENSSL_HEADER_HKDF_H
#define OPENSSL_HEADER_HKDF_H

#include <openssl/base.h>

#ifdef  __cplusplus
extern "C" {
#endif


/* Computes HKDF (as specified by RFC 5869) of initial keying material |secret|
 * with |salt| and |info| using |digest|, and outputs |out_len| bytes to
 * |out_key|. It returns one on success and zero on error.
 *
 * HKDF is an Extract-and-Expand algorithm. It does not do any key stretching,
 * and as such, is not suited to be used alone to generate a key from a
 * password. */
OPENSSL_EXPORT int HKDF(uint8_t *out_key, size_t out_len, const EVP_MD *digest,
                        const uint8_t *secret, size_t secret_len,
                        const uint8_t *salt, size_t salt_len,
                        const uint8_t *info, size_t info_len);


#if defined(__cplusplus)
}  /* extern C */
#endif

#define HKDF_R_OUTPUT_TOO_LARGE 100

#endif  /* OPENSSL_HEADER_HKDF_H */
