1EVP_KDF_CTX(3)                      OpenSSL                     EVP_KDF_CTX(3)
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NAME

6       EVP_KDF_CTX, EVP_KDF_CTX_new_id, EVP_KDF_CTX_free, EVP_KDF_reset,
7       EVP_KDF_ctrl, EVP_KDF_vctrl, EVP_KDF_ctrl_str, EVP_KDF_size,
8       EVP_KDF_derive - EVP KDF routines
9

SYNOPSIS

11        #include <openssl/kdf.h>
12
13        typedef struct evp_kdf_ctx_st EVP_KDF_CTX;
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15        EVP_KDF_CTX *EVP_KDF_CTX_new_id(int id);
16        void EVP_KDF_CTX_free(EVP_KDF_CTX *ctx);
17        void EVP_KDF_reset(EVP_KDF_CTX *ctx);
18        int EVP_KDF_ctrl(EVP_KDF_CTX *ctx, int cmd, ...);
19        int EVP_KDF_vctrl(EVP_KDF_CTX *ctx, int cmd, va_list args);
20        int EVP_KDF_ctrl_str(EVP_KDF_CTX *ctx, const char *type, const char *value);
21        size_t EVP_KDF_size(EVP_KDF_CTX *ctx);
22        int EVP_KDF_derive(EVP_KDF_CTX *ctx, unsigned char *key, size_t keylen);
23

DESCRIPTION

25       The EVP KDF routines are a high level interface to Key Derivation
26       Function algorithms and should be used instead of algorithm-specific
27       functions.
28
29       After creating a "EVP_KDF_CTX" for the required algorithm using
30       EVP_KDF_CTX_new_id(), inputs to the algorithm are supplied using calls
31       to EVP_KDF_ctrl(), EVP_KDF_vctrl() or EVP_KDF_ctrl_str() before calling
32       EVP_KDF_derive() to derive the key.
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34   Types
35       EVP_KDF_CTX is a context type that holds the algorithm inputs.
36
37   Context manipulation functions
38       EVP_KDF_CTX_new_id() creates a KDF context for the algorithm identified
39       by the specified NID.
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41       EVP_KDF_CTX_free() frees up the context "ctx".  If "ctx" is "NULL",
42       nothing is done.
43
44   Computing functions
45       EVP_KDF_reset() resets the context to the default state as if the
46       context had just been created.
47
48       EVP_KDF_ctrl() is used to provide inputs to the KDF algorithm prior to
49       EVP_KDF_derive() being called.  The inputs that may be provided will
50       vary depending on the KDF algorithm or its implementation.  This
51       functions takes variable arguments, the exact expected arguments depend
52       on "cmd".  See "CONTROLS" below for a description of standard controls.
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54       EVP_KDF_vctrl() is the variant of EVP_KDF_ctrl() that takes a "va_list"
55       argument instead of variadic arguments.
56
57       EVP_KDF_ctrl_str() allows an application to send an algorithm specific
58       control operation to a context "ctx" in string form.  This is intended
59       to be used for options specified on the command line or in text files.
60
61       EVP_KDF_size() returns the output size if the algorithm produces a
62       fixed amount of output and "SIZE_MAX" otherwise.  If an error occurs
63       then 0 is returned.  For some algorithms an error may result if input
64       parameters necessary to calculate a fixed output size have not yet been
65       supplied.
66
67       EVP_KDF_derive() derives "keylen" bytes of key material and places it
68       in the "key" buffer.  If the algorithm produces a fixed amount of
69       output then an error will occur unless the "keylen" parameter is equal
70       to that output size, as returned by EVP_KDF_size().
71

CONTROLS

73       The standard controls are:
74
75       EVP_KDF_CTRL_SET_PASS
76           This control expects two arguments: "unsigned char *pass", "size_t
77           passlen"
78
79           Some KDF implementations require a password.  For those KDF
80           implementations that support it, this control sets the password.
81
82           EVP_KDF_ctrl_str() takes two type strings for this control:
83
84           "pass"
85               The value string is used as is.
86
87           "hexpass"
88               The value string is expected to be a hexadecimal number, which
89               will be decoded before being passed on as the control value.
90
91       EVP_KDF_CTRL_SET_SALT
92           This control expects two arguments: "unsigned char *salt", "size_t
93           saltlen"
94
95           Some KDF implementations can take a salt.  For those KDF
96           implementations that support it, this control sets the salt.
97
98           The default value, if any, is implementation dependent.
99
100           EVP_KDF_ctrl_str() takes two type strings for this control:
101
102           "salt"
103               The value string is used as is.
104
105           "hexsalt"
106               The value string is expected to be a hexadecimal number, which
107               will be decoded before being passed on as the control value.
108
109       EVP_KDF_CTRL_SET_ITER
110           This control expects one argument: "int iter"
111
112           Some KDF implementations require an iteration count. For those KDF
113           implementations that support it, this control sets the iteration
114           count.
115
116           The default value, if any, is implementation dependent.
117
118           EVP_KDF_ctrl_str() type string: "iter"
119
120           The value string is expected to be a decimal number.
121
122       EVP_KDF_CTRL_SET_MD
123           This control expects one argument: "EVP_MD *md"
124
125           For MAC implementations that use a message digest as an underlying
126           computation algorithm, this control sets what the digest algorithm
127           should be.
128
129       EVP_KDF_CTRL_SET_CIPHER
130           This control expects one argument: "EVP_CIPHER *cipher"
131
132           For MAC implementations that use a cipher as an underlying
133           computation algorithm, this control sets what the cipher algorithm
134           should be.
135
136           EVP_KDF_ctrl_str() type string: "md"
137
138           The value string is expected to be the name of a digest.
139
140       EVP_KDF_CTRL_SET_KEY
141           This control expects two arguments: "unsigned char *key", "size_t
142           keylen"
143
144           Some KDF implementations require a key.  For those KDF
145           implementations that support it, this control sets the key.
146
147           EVP_KDF_ctrl_str() takes two type strings for this control:
148
149           "key"
150               The value string is used as is.
151
152           "hexkey"
153               The value string is expected to be a hexadecimal number, which
154               will be decoded before being passed on as the control value.
155
156       EVP_KDF_CTRL_SET_MAXMEM_BYTES
157           This control expects one argument: "uint64_t maxmem_bytes"
158
159           Memory-hard password-based KDF algorithms, such as scrypt, use an
160           amount of memory that depends on the load factors provided as
161           input.  For those KDF implementations that support it, this control
162           sets an upper limit on the amount of memory that may be consumed
163           while performing a key derivation.  If this memory usage limit is
164           exceeded because the load factors are chosen too high, the key
165           derivation will fail.
166
167           The default value is implementation dependent.
168
169           EVP_KDF_ctrl_str() type string: "maxmem_bytes"
170
171           The value string is expected to be a decimal number.
172

RETURN VALUES

174       EVP_KDF_CTX_new_id() returns either the newly allocated "EVP_KDF_CTX"
175       structure or "NULL" if an error occurred.
176
177       EVP_KDF_CTX_free() and EVP_KDF_reset() do not return a value.
178
179       EVP_KDF_size() returns the output size.  "SIZE_MAX" is returned to
180       indicate that the algorithm produces a variable amount of output; 0 to
181       indicate failure.
182
183       The remaining functions return 1 for success and 0 or a negative value
184       for failure.  In particular, a return value of -2 indicates the
185       operation is not supported by the KDF algorithm.
186

SEE ALSO

188       EVP_KDF_SCRYPT(7)
189

191       Copyright 2018 The OpenSSL Project Authors. All Rights Reserved.
192
193       Licensed under the Apache License 2.0 (the "License").  You may not use
194       this file except in compliance with the License.  You can obtain a copy
195       in the file LICENSE in the source distribution or at
196       <https://www.openssl.org/source/license.html>.
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2001.1.1i                            2021-07-22                    EVP_KDF_CTX(3)
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