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EVP_KDF_CTX(3)                      OpenSSL                     EVP_KDF_CTX(3)
NAME
       EVP_KDF_CTX, EVP_KDF_CTX_new_id, EVP_KDF_CTX_free, EVP_KDF_reset,
       EVP_KDF_ctrl, EVP_KDF_vctrl, EVP_KDF_ctrl_str, EVP_KDF_size,
       EVP_KDF_derive - EVP KDF routines
SYNOPSIS
        #include <openssl/kdf.h>
        typedef struct evp_kdf_ctx_st EVP_KDF_CTX;
        EVP_KDF_CTX *EVP_KDF_CTX_new_id(int id);
        void EVP_KDF_CTX_free(EVP_KDF_CTX *ctx);
        void EVP_KDF_reset(EVP_KDF_CTX *ctx);
        int EVP_KDF_ctrl(EVP_KDF_CTX *ctx, int cmd, ...);
        int EVP_KDF_vctrl(EVP_KDF_CTX *ctx, int cmd, va_list args);
        int EVP_KDF_ctrl_str(EVP_KDF_CTX *ctx, const char *type, const char *value);
        size_t EVP_KDF_size(EVP_KDF_CTX *ctx);
        int EVP_KDF_derive(EVP_KDF_CTX *ctx, unsigned char *key, size_t keylen);
DESCRIPTION
       The EVP KDF routines are a high level interface to Key Derivation
       Function algorithms and should be used instead of algorithm-specific
       functions.
       After creating a "EVP_KDF_CTX" for the required algorithm using
       EVP_KDF_CTX_new_id(), inputs to the algorithm are supplied using calls
       to EVP_KDF_ctrl(), EVP_KDF_vctrl() or EVP_KDF_ctrl_str() before calling
       EVP_KDF_derive() to derive the key.
   Types
       EVP_KDF_CTX is a context type that holds the algorithm inputs.
   Context manipulation functions
       EVP_KDF_CTX_new_id() creates a KDF context for the algorithm identified
       by the specified NID.
       EVP_KDF_CTX_free() frees up the context "ctx".  If "ctx" is "NULL",
       nothing is done.
   Computing functions
       EVP_KDF_reset() resets the context to the default state as if the
       context had just been created.
       EVP_KDF_ctrl() is used to provide inputs to the KDF algorithm prior to
       EVP_KDF_derive() being called.  The inputs that may be provided will
       vary depending on the KDF algorithm or its implementation.  This
       functions takes variable arguments, the exact expected arguments depend
       on "cmd".  See "CONTROLS" below for a description of standard controls.
       EVP_KDF_vctrl() is the variant of EVP_KDF_ctrl() that takes a "va_list"
       argument instead of variadic arguments.
       EVP_KDF_ctrl_str() allows an application to send an algorithm specific
       control operation to a context "ctx" in string form.  This is intended
       to be used for options specified on the command line or in text files.
       EVP_KDF_size() returns the output size if the algorithm produces a
       fixed amount of output and "SIZE_MAX" otherwise.  If an error occurs
       then 0 is returned.  For some algorithms an error may result if input
       parameters necessary to calculate a fixed output size have not yet been
       supplied.
       EVP_KDF_derive() derives "keylen" bytes of key material and places it
       in the "key" buffer.  If the algorithm produces a fixed amount of
       output then an error will occur unless the "keylen" parameter is equal
       to that output size, as returned by EVP_KDF_size().
CONTROLS
       The standard controls are:
       EVP_KDF_CTRL_SET_PASS
           This control expects two arguments: "unsigned char *pass", "size_t
           passlen"
           Some KDF implementations require a password.  For those KDF
           implementations that support it, this control sets the password.
           EVP_KDF_ctrl_str() takes two type strings for this control:
           "pass"
               The value string is used as is.
           "hexpass"
               The value string is expected to be a hexadecimal number, which
               will be decoded before being passed on as the control value.
       EVP_KDF_CTRL_SET_SALT
           This control expects two arguments: "unsigned char *salt", "size_t
           saltlen"
           Some KDF implementations can take a salt.  For those KDF
           implementations that support it, this control sets the salt.
           The default value, if any, is implementation dependent.
           EVP_KDF_ctrl_str() takes two type strings for this control:
           "salt"
               The value string is used as is.
           "hexsalt"
               The value string is expected to be a hexadecimal number, which
               will be decoded before being passed on as the control value.
       EVP_KDF_CTRL_SET_ITER
           This control expects one argument: "int iter"
           Some KDF implementations require an iteration count. For those KDF
           implementations that support it, this control sets the iteration
           count.
           The default value, if any, is implementation dependent.
           EVP_KDF_ctrl_str() type string: "iter"
           The value string is expected to be a decimal number.
       EVP_KDF_CTRL_SET_MD
           This control expects one argument: "EVP_MD *md"
           For MAC implementations that use a message digest as an underlying
           computation algorithm, this control sets what the digest algorithm
           should be.
       EVP_KDF_CTRL_SET_CIPHER
           This control expects one argument: "EVP_CIPHER *cipher"
           For MAC implementations that use a cipher as an underlying
           computation algorithm, this control sets what the cipher algorithm
           should be.
           EVP_KDF_ctrl_str() type string: "md"
           The value string is expected to be the name of a digest.
       EVP_KDF_CTRL_SET_KEY
           This control expects two arguments: "unsigned char *key", "size_t
           keylen"
           Some KDF implementations require a key.  For those KDF
           implementations that support it, this control sets the key.
           EVP_KDF_ctrl_str() takes two type strings for this control:
           "key"
               The value string is used as is.
           "hexkey"
               The value string is expected to be a hexadecimal number, which
               will be decoded before being passed on as the control value.
       EVP_KDF_CTRL_SET_MAXMEM_BYTES
           This control expects one argument: "uint64_t maxmem_bytes"
           Memory-hard password-based KDF algorithms, such as scrypt, use an
           amount of memory that depends on the load factors provided as
           input.  For those KDF implementations that support it, this control
           sets an upper limit on the amount of memory that may be consumed
           while performing a key derivation.  If this memory usage limit is
           exceeded because the load factors are chosen too high, the key
           derivation will fail.
           The default value is implementation dependent.
           EVP_KDF_ctrl_str() type string: "maxmem_bytes"
           The value string is expected to be a decimal number.
RETURN VALUES
       EVP_KDF_CTX_new_id() returns either the newly allocated "EVP_KDF_CTX"
       structure or "NULL" if an error occurred.
       EVP_KDF_CTX_free() and EVP_KDF_reset() do not return a value.
       EVP_KDF_size() returns the output size.  "SIZE_MAX" is returned to
       indicate that the algorithm produces a variable amount of output; 0 to
       indicate failure.
       The remaining 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 KDF algorithm.
SEE ALSO
       EVP_KDF_SCRYPT(7)
COPYRIGHT
       Copyright 2018 The OpenSSL Project Authors. All Rights Reserved.
       Licensed under the Apache License 2.0 (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>;.
1.1.1k                            2024-10-09                    EVP_KDF_CTX(3)