mirror of https://github.com/openssl/openssl
109 lines
2.8 KiB
Plaintext
109 lines
2.8 KiB
Plaintext
=pod
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=head1 NAME
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EVP_KDF-X963 - The X9.63-2001 EVP_KDF implementation
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=head1 DESCRIPTION
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The EVP_KDF-X963 algorithm implements the key derivation function (X963KDF).
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X963KDF is used by Cryptographic Message Syntax (CMS) for EC KeyAgreement, to
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derive a key using input such as a shared secret key and shared info.
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=head2 Identity
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"X963KDF" is the name for this implementation; it
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can be used with the EVP_KDF_fetch() function.
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=head2 Supported parameters
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The supported parameters are:
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=over 4
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=item "properties" (B<OSSL_KDF_PARAM_PROPERTIES>) <UTF8 string>
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=item "digest" (B<OSSL_KDF_PARAM_DIGEST>) <UTF8 string>
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These parameters work as described in L<EVP_KDF(3)/PARAMETERS>.
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=item "key" (B<OSSL_KDF_PARAM_KEY>) <octet string>
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The shared secret used for key derivation.
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This parameter sets the secret.
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=item "info" (B<OSSL_KDF_PARAM_INFO>) <octet string>
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This parameter specifies an optional value for shared info.
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=back
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=head1 NOTES
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X963KDF is very similar to the SSKDF that uses a digest as the auxiliary function,
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X963KDF appends the counter to the secret, whereas SSKDF prepends the counter.
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A context for X963KDF can be obtained by calling:
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EVP_KDF *kdf = EVP_KDF_fetch(NULL, "X963KDF", NULL);
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EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf);
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The output length of an X963KDF is specified via the I<keylen>
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parameter to the L<EVP_KDF_derive(3)> function.
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=head1 EXAMPLES
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This example derives 10 bytes, with the secret key "secret" and sharedinfo
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value "label":
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EVP_KDF *kdf;
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EVP_KDF_CTX *kctx;
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unsigned char out[10];
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OSSL_PARAM params[4], *p = params;
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kdf = EVP_KDF_fetch(NULL, "X963KDF", NULL);
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kctx = EVP_KDF_CTX_new(kdf);
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EVP_KDF_free(kdf);
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*p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
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SN_sha256, strlen(SN_sha256));
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*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SECRET,
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"secret", (size_t)6);
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*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO,
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"label", (size_t)5);
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*p = OSSL_PARAM_construct_end();
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if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0) {
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error("EVP_KDF_derive");
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}
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EVP_KDF_CTX_free(kctx);
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=head1 CONFORMING TO
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"SEC 1: Elliptic Curve Cryptography"
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=head1 SEE ALSO
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L<EVP_KDF(3)>,
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L<EVP_KDF_CTX_new(3)>,
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L<EVP_KDF_CTX_free(3)>,
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L<EVP_KDF_CTX_set_params(3)>,
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L<EVP_KDF_CTX_get_kdf_size(3)>,
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L<EVP_KDF_derive(3)>,
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L<EVP_KDF(3)/PARAMETERS>
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=head1 HISTORY
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This functionality was added in OpenSSL 3.0.
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=head1 COPYRIGHT
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Copyright 2019-2021 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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