EVP_PKEY-HMAC, EVP_KEYMGMT-HMAC, EVP_PKEY-Siphash, EVP_KEYMGMT-Siphash,
  EVP_PKEY-Poly1305, EVP_KEYMGMT-Poly1305, EVP_PKEY-CMAC, EVP_KEYMGMT-CMAC -
  EVP_PKEY legacy MAC keytypes and algorithm support
The HMAC and CMAC key types are implemented in OpenSSL's default
  and FIPS providers. Additionally the Siphash and Poly1305 key
  types are implemented in the default provider. Performing MAC operations via
  an EVP_PKEY is considered legacy and are only available for backwards
  compatibility purposes and for a restricted set of algorithms. The preferred
  way of performing MAC operations is via the EVP_MAC APIs. See
  EVP_MAC_init(3).
For further details on using EVP_PKEY based MAC keys see
    EVP_SIGNATURE-HMAC(7), EVP_SIGNATURE-Siphash(7),
    EVP_SIGNATURE-Poly1305(7) or EVP_SIGNATURE-CMAC(7).
All the MAC keytypes support the following parameters.
  - "priv" (OSSL_PKEY_PARAM_PRIV_KEY) <octet
    string>
- The MAC key value.
- "properties" (OSSL_PKEY_PARAM_PROPERTIES) <UTF8
    string>
- A property query string to be used when any algorithms are fetched.
As well as the parameters described above, the CMAC keytype additionally
  supports the following parameters.
  - "cipher" (OSSL_PKEY_PARAM_CIPHER) <UTF8
    string>
- The name of a cipher to be used when generating the MAC.
- "engine" (OSSL_PKEY_PARAM_ENGINE) <UTF8
    string>
- The name of an engine to be used for the specified cipher (if any).
MAC key generation is unusual in that no new key is actually generated. Instead
  a new provider side key object is created with the supplied raw key value.
  This is done for backwards compatibility with previous versions of OpenSSL.
  - "priv" (OSSL_PKEY_PARAM_PRIV_KEY) <octet
    string>
- The MAC key value.
In addition to the common MAC key generation parameters, the CMAC key generation
  additionally recognises the following.
  - "cipher" (OSSL_PKEY_PARAM_CIPHER) <UTF8
    string>
- The name of a cipher to be used when generating the MAC.
EVP_KEYMGMT(3), EVP_PKEY(3), provider-keymgmt(7)
Copyright 2020 The OpenSSL Project Authors. All Rights Reserved.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>.