1EVP_KDF_SS(7)                       OpenSSL                      EVP_KDF_SS(7)
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NAME

6       EVP_KDF_SS - The Single Step / One Step EVP_KDF implementation
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DESCRIPTION

9       The EVP_KDF_SS algorithm implements the Single Step key derivation
10       function (SSKDF).  SSKDF derives a key using input such as a shared
11       secret key (that was generated during the execution of a key
12       establishment scheme) and fixedinfo.  SSKDF is also informally referred
13       to as 'Concat KDF'.
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15   Auxilary function
16       The implementation uses a selectable auxiliary function H, which can be
17       in the backported version only a:
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19       H(x) = hash(x, digest=md)
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21   Numeric identity
22       EVP_KDF_SS is the numeric identity for this implementation; it can be
23       used with the EVP_KDF_CTX_new_id() function.
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25   Supported controls
26       The supported controls are:
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28       EVP_KDF_CTRL_SET_MD
29           This control works as described in "CONTROLS" in EVP_KDF_CTX(3).
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31       EVP_KDF_CTRL_SET_KEY
32           This control expects two arguments: "unsigned char *secret",
33           "size_t secretlen"
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35           The shared secret used for key derivation.  This control sets the
36           secret.
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38           EVP_KDF_ctrl_str() takes two type strings for this control:
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40           "secret"
41               The value string is used as is.
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43           "hexsecret"
44               The value string is expected to be a hexadecimal number, which
45               will be decoded before being passed on as the control value.
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47       EVP_KDF_CTRL_SET_SSKDF_INFO
48           This control expects two arguments: "unsigned char *info", "size_t
49           infolen"
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51           An optional value for fixedinfo, also known as otherinfo. This
52           control sets the fixedinfo.
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54           EVP_KDF_ctrl_str() takes two type strings for this control:
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56           "info"
57               The value string is used as is.
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59           "hexinfo"
60               The value string is expected to be a hexadecimal number, which
61               will be decoded before being passed on as the control value.
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NOTES

64       A context for SSKDF can be obtained by calling:
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66       EVP_KDF_CTX *kctx = EVP_KDF_CTX_new_id(EVP_KDF_SS);
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68       The output length of an SSKDF is specified via the "keylen" parameter
69       to the EVP_KDF_derive(3) function.
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EXAMPLE

72       This example derives 10 bytes using H(x) = SHA-256, with the secret key
73       "secret" and fixedinfo value "label":
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75         EVP_KDF_CTX *kctx;
76         unsigned char out[10];
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78         kctx = EVP_KDF_CTX_new_id(EVP_KDF_SS);
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80         if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_SET_MD, EVP_sha256()) <= 0) {
81             error("EVP_KDF_CTRL_SET_MD");
82         }
83         if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_SET_KEY, "secret", (size_t)6) <= 0) {
84             error("EVP_KDF_CTRL_SET_KEY");
85         }
86         if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_SET_SSKDF_INFO, "label", (size_t)5) <= 0) {
87             error("EVP_KDF_CTRL_SET_SSKDF_INFO");
88         }
89         if (EVP_KDF_derive(kctx, out, sizeof(out)) <= 0) {
90             error("EVP_KDF_derive");
91         }
92
93         EVP_KDF_CTX_free(kctx);
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CONFORMING TO

96       NIST SP800-56Cr1.
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SEE ALSO

99       EVP_KDF_CTX, EVP_KDF_CTX_new_id(3), EVP_KDF_CTX_free(3),
100       EVP_KDF_ctrl(3), EVP_KDF_size(3), EVP_KDF_derive(3), "CONTROLS" in
101       EVP_KDF_CTX(3)
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HISTORY

104       This functionality was added to OpenSSL 3.0.0.
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107       Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
108       Copyright (c) 2019, Oracle and/or its affiliates.  All rights reserved.
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110       Licensed under the Apache License 2.0 (the "License").  You may not use
111       this file except in compliance with the License.  You can obtain a copy
112       in the file LICENSE in the source distribution or at
113       <https://www.openssl.org/source/license.html>.
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1171.1.1l                            2021-09-15                     EVP_KDF_SS(7)
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