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      1 /* Copyright (c) 2014, Google Inc.
      2  *
      3  * Permission to use, copy, modify, and/or distribute this software for any
      4  * purpose with or without fee is hereby granted, provided that the above
      5  * copyright notice and this permission notice appear in all copies.
      6  *
      7  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
      8  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
      9  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
     10  * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
     11  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
     12  * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
     13  * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
     14 
     15 #ifndef OPENSSL_HEADER_HKDF_H
     16 #define OPENSSL_HEADER_HKDF_H
     17 
     18 #include <openssl/base.h>
     19 
     20 #ifdef  __cplusplus
     21 extern "C" {
     22 #endif
     23 
     24 
     25 /* Computes HKDF (as specified by RFC 5869) of initial keying material |secret|
     26  * with |salt| and |info| using |digest|, and outputs |out_len| bytes to
     27  * |out_key|. It returns one on success and zero on error.
     28  *
     29  * HKDF is an Extract-and-Expand algorithm. It does not do any key stretching,
     30  * and as such, is not suited to be used alone to generate a key from a
     31  * password. */
     32 OPENSSL_EXPORT int HKDF(uint8_t *out_key, size_t out_len, const EVP_MD *digest,
     33                         const uint8_t *secret, size_t secret_len,
     34                         const uint8_t *salt, size_t salt_len,
     35                         const uint8_t *info, size_t info_len);
     36 
     37 
     38 #if defined(__cplusplus)
     39 }  /* extern C */
     40 #endif
     41 
     42 #define HKDF_R_OUTPUT_TOO_LARGE 100
     43 
     44 #endif  /* OPENSSL_HEADER_HKDF_H */
     45