NAME

       EVP_PKEY_CTX_set1_scrypt_salt, EVP_PKEY_CTX_set_scrypt_N, EVP_PKEY_CTX_set_scrypt_r,
       EVP_PKEY_CTX_set_scrypt_p, EVP_PKEY_CTX_set_scrypt_maxmem_bytes - EVP_PKEY scrypt KDF
       support functions

SYNOPSIS

        #include <openssl/kdf.h>

        int EVP_PKEY_CTX_set1_scrypt_salt(EVP_PKEY_CTX *pctx, unsigned char *salt,
                                          int saltlen);

        int EVP_PKEY_CTX_set_scrypt_N(EVP_PKEY_CTX *pctx, uint64_t N);

        int EVP_PKEY_CTX_set_scrypt_r(EVP_PKEY_CTX *pctx, uint64_t r);

        int EVP_PKEY_CTX_set_scrypt_p(EVP_PKEY_CTX *pctx, uint64_t p);

        int EVP_PKEY_CTX_set_scrypt_maxmem_bytes(EVP_PKEY_CTX *pctx,
                                                 uint64_t maxmem);

DESCRIPTION

       These functions are used to set up the necessary data to use the scrypt KDF.  For more
       information on scrypt, see scrypt(7).

       EVP_PKEY_CTX_set1_scrypt_salt() sets the saltlen bytes long salt value.

       EVP_PKEY_CTX_set_scrypt_N(), EVP_PKEY_CTX_set_scrypt_r() and EVP_PKEY_CTX_set_scrypt_p()
       configure the work factors N, r and p.

       EVP_PKEY_CTX_set_scrypt_maxmem_bytes() sets how much RAM key derivation may maximally use,
       given in bytes.  If RAM is exceeded because the load factors are chosen too high, the key
       derivation will fail.

STRING CTRLS

       scrypt also supports string based control operations via EVP_PKEY_CTX_ctrl_str(3).
       Similarly, the salt can either be specified using the type parameter "salt" or in hex
       encoding by using the "hexsalt" parameter.  The work factors N, r and p as well as
       maxmem_bytes can be set by using the parameters "N", "r", "p" and "maxmem_bytes",
       respectively.

NOTES

       The scrypt KDF also uses EVP_PKEY_CTX_set1_pbe_pass() as well as the value from the string
       controls "pass" and "hexpass".  See EVP_PKEY_CTX_set1_pbe_pass(3).

       All the functions described here are implemented as macros.

RETURN VALUES

       All these functions return 1 for success and 0 or a negative value for failure.  In
       particular a return value of -2 indicates the operation is not supported by the public key
       algorithm.

SEE ALSO

       scrypt(7), EVP_PKEY_CTX_new(3), EVP_PKEY_CTX_ctrl_str(3), EVP_PKEY_derive(3)

COPYRIGHT

       Copyright 2017-2018 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (the "License").  You may not use this file except in
       compliance with the License.  You can obtain a copy in the file LICENSE in the source
       distribution or at <https://www.openssl.org/source/license.html>.