Depending on whether mac is CMAC or HMAC, either digest or cipher is required (respectively) and the other is unused.
The parameters key, salt, info, and seed correspond to KI, Label, Context, and IV (respectively) in SP800-108. As in that document, salt, info, and seed are optional and may be omitted.
``mac'', ``digest'', cipher`` and ''properties" are described in ``PARAMETERS'' in EVP_KDF(3).
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 "keylen" parameter to the EVP_KDF_derive(3) function.
Note that currently OpenSSL only implements counter and feedback modes. Other variants may be supported in the future.
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, "SHA2-256", 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, "label", strlen("label")); *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO, "context", strlen("context")); *p = OSSL_PARAM_construct_end(); if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0) error("EVP_KDF_derive"); EVP_KDF_CTX_free(kctx);
This example derives 10 bytes using FEEDBACK-CMAC-AES256, with KI ``secret'', Label ``label'', and IV ``sixteen bytes iv''.
EVP_KDF *kdf; EVP_KDF_CTX *kctx; unsigned char out[10]; OSSL_PARAM params[8], *p = params; unsigned char *iv = "sixteen bytes iv"; 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_CIPHER, "AES256", 0); *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MAC, "CMAC", 0); *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MODE, "FEEDBACK", 0); *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_KEY, "secret", strlen("secret")); *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT, "label", strlen("label")); *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO, "context", strlen("context")); *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SEED, iv, strlen(iv)); *p = OSSL_PARAM_construct_end(); if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0) error("EVP_KDF_derive"); EVP_KDF_CTX_free(kctx);
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 <https://www.openssl.org/source/license.html>.