| =pod |
| |
| =head1 NAME |
| |
| EVP_KDF-KB - The Key-Based EVP_KDF implementation |
| |
| =head1 DESCRIPTION |
| |
| The EVP_KDF-KB algorithm implements the Key-Based key derivation function |
| (KBKDF). KBKDF derives a key from repeated application of a keyed MAC to an |
| input secret (and other optional values). |
| |
| =head2 Identity |
| |
| "KBKDF" is the name for this implementation; it can be used with the |
| EVP_KDF_fetch() function. |
| |
| =head2 Supported parameters |
| |
| The supported parameters are: |
| |
| =over 4 |
| |
| =item B<OSSL_KDF_PARAM_PROPERTIES> ("properties") <UTF8 string> |
| |
| =item B<OSSL_KDF_PARAM_DIGEST> ("digest") <UTF8 string> |
| |
| =item B<OSSL_KDF_PARAM_DIGEST> ("mac") <UTF8 string> |
| |
| =item B<OSSL_KDF_PARAM_KEY> ("key") <octet string> |
| |
| =item B<OSSL_KDF_PARAM_SALT> ("salt") <octet string> |
| |
| =item B<OSSL_KDF_PARAM_INFO> ("info") <octet string> |
| |
| =back |
| |
| The parameters key, salt, and info correspond to KI, Label, and Context |
| (respectively) in SP800-108. As in that document, salt and info are optional |
| and may be omitted. Currently, only HMAC is supported for mac. |
| |
| =head1 NOTES |
| |
| A context for KBKDF can be obtained by calling: |
| |
| EVP_KDF *kdf = EVP_KDF_fetch(NULL, "KBKDF", NULL); |
| EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf); |
| |
| The output length of an KBKDF is specified via the C<keylen> |
| parameter to the L<EVP_KDF_derive(3)> function. |
| |
| Note that currently OpenSSL only implements Counter mode with HMAC. Other |
| variants may be supported in the future. |
| |
| =head1 EXAMPLES |
| |
| This example derives 10 bytes using COUNTER-HMAC-SHA256, with KI "secret", |
| Label "label", and Context "context". |
| |
| EVP_KDF *kdf; |
| EVP_KDF_CTX *kctx; |
| unsigned char out[10]; |
| OSSL_PARAM params[6], *p = params; |
| |
| kdf = EVP_KDF_fetch(NULL, "KBKDF", NULL); |
| kctx = EVP_KDF_CTX_new(kdf); |
| EVP_KDF_free(kdf); |
| |
| *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST, |
| "SHA256", 0); |
| *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MAC, |
| "HMAC", 0); |
| *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_KEY, |
| "secret", strlen("secret")) |
| *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT, |
| "context", strlen("context")); |
| *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO, |
| "label", strlen("label")); |
| *p = OSSL_PARAM_construct_end(); |
| if (EVP_KDF_CTX_set_params(kctx, params) <= 0) |
| error("EVP_KDF_CTX_set_params"); |
| else if (EVP_KDF_derive(kctx, out, sizeof(out)) <= 0) |
| error("EVP_KDF_derive"); |
| |
| EVP_KDF_CTX_free(kctx); |
| |
| =head1 CONFORMING TO |
| |
| NIST SP800-108, IETF RFC 8009. |
| |
| =head1 SEE ALSO |
| |
| L<EVP_KDF(3)>, |
| L<EVP_KDF_CTX_new_id(3)>, |
| L<EVP_KDF_CTX_free(3)>, |
| L<EVP_KDF_ctrl(3)>, |
| L<EVP_KDF_size(3)>, |
| L<EVP_KDF_derive(3)>, |
| L<EVP_KDF(3)/PARAMETERS> |
| |
| =head1 HISTORY |
| |
| This functionality was added to OpenSSL 3.0. |
| |
| =head1 COPYRIGHT |
| |
| Copyright 2019 The OpenSSL Project Authors. All Rights Reserved. |
| Copyright 2019 Red Hat, Inc. |
| |
| 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 |
| L<https://www.openssl.org/source/license.html>. |
| |
| =cut |
