1EVP_KDF-X963(7ossl)                 OpenSSL                EVP_KDF-X963(7ossl)
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NAME

6       EVP_KDF-X963 - The X9.63-2001 EVP_KDF implementation
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DESCRIPTION

9       The EVP_KDF-X963 algorithm implements the key derivation function
10       (X963KDF).  X963KDF is used by Cryptographic Message Syntax (CMS) for
11       EC KeyAgreement, to derive a key using input such as a shared secret
12       key and shared info.
13
14   Identity
15       "X963KDF" is the name for this implementation; it can be used with the
16       EVP_KDF_fetch() function.
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18   Supported parameters
19       The supported parameters are:
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21       "properties" (OSSL_KDF_PARAM_PROPERTIES) <UTF8 string>
22       "digest" (OSSL_KDF_PARAM_DIGEST) <UTF8 string>
23           These parameters work as described in "PARAMETERS" in EVP_KDF(3).
24
25       "key" (OSSL_KDF_PARAM_KEY) <octet string>
26           The shared secret used for key derivation.  This parameter sets the
27           secret.
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29       "info" (OSSL_KDF_PARAM_INFO) <octet string>
30           This parameter specifies an optional value for shared info.
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NOTES

33       X963KDF is very similar to the SSKDF that uses a digest as the
34       auxiliary function, X963KDF appends the counter to the secret, whereas
35       SSKDF prepends the counter.
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37       A context for X963KDF can be obtained by calling:
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39        EVP_KDF *kdf = EVP_KDF_fetch(NULL, "X963KDF", NULL);
40        EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf);
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42       The output length of an X963KDF is specified via the keylen parameter
43       to the EVP_KDF_derive(3) function.
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EXAMPLES

46       This example derives 10 bytes, with the secret key "secret" and
47       sharedinfo value "label":
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49        EVP_KDF *kdf;
50        EVP_KDF_CTX *kctx;
51        unsigned char out[10];
52        OSSL_PARAM params[4], *p = params;
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54        kdf = EVP_KDF_fetch(NULL, "X963KDF", NULL);
55        kctx = EVP_KDF_CTX_new(kdf);
56        EVP_KDF_free(kdf);
57
58        *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
59                                                SN_sha256, strlen(SN_sha256));
60        *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SECRET,
61                                                 "secret", (size_t)6);
62        *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO,
63                                                 "label", (size_t)5);
64        *p = OSSL_PARAM_construct_end();
65        if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0) {
66            error("EVP_KDF_derive");
67        }
68
69        EVP_KDF_CTX_free(kctx);
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CONFORMING TO

72       "SEC 1: Elliptic Curve Cryptography"
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SEE ALSO

75       EVP_KDF(3), EVP_KDF_CTX_new(3), EVP_KDF_CTX_free(3),
76       EVP_KDF_CTX_set_params(3), EVP_KDF_CTX_get_kdf_size(3),
77       EVP_KDF_derive(3), "PARAMETERS" in EVP_KDF(3)
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HISTORY

80       This functionality was added in OpenSSL 3.0.
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83       Copyright 2019-2021 The OpenSSL Project Authors. All Rights Reserved.
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85       Licensed under the Apache License 2.0 (the "License").  You may not use
86       this file except in compliance with the License.  You can obtain a copy
87       in the file LICENSE in the source distribution or at
88       <https://www.openssl.org/source/license.html>.
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923.0.9                             2023-07-27               EVP_KDF-X963(7ossl)
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