EVP_MAC-HMAC(7ssl)

EVP_MAC-HMAC7ssl

The hmac evp_mac implementation

Overview

Support for computing HMAC MACs through the EVP_MAC API.

This implementation uses EVP_MD functions to get access to the underlying digest.

Identity

This implementation is identified with this name and properties, to be used with EVP_MAC_fetch():

"HMAC", "provider=default" or "provider=fips"

Supported parameters

The general description of these parameters can be found in "PARAMETERS" in EVP_MAC(3).

The following parameters can be set with EVP_MAC_CTX_set_params():

"key" (OSSL_MAC_PARAM_KEY) <octet string>

Sets the MAC key. Setting this parameter is identical to passing a key to EVP_MAC_init(3).

"digest" (OSSL_MAC_PARAM_DIGEST) <UTF8 string>

Sets the name of the underlying digest to be used.

"properties" (OSSL_MAC_PARAM_PROPERTIES) <UTF8 string>

Sets the properties to be queried when trying to fetch the underlying digest. This must be given together with the digest naming parameter ("digest", or OSSL_MAC_PARAM_DIGEST) to be considered valid.

"digest-noinit" (OSSL_MAC_PARAM_DIGEST_NOINIT) <integer>

A flag to set the MAC digest to not initialise the implementation specific data. The value 0 or 1 is expected. This option is deprecated and will be removed in a future release. It may be set but is currently ignored

"digest-oneshot" (OSSL_MAC_PARAM_DIGEST_ONESHOT) <integer>

A flag to set the MAC digest to be a one-shot operation. The value 0 or 1 is expected. This option is deprecated and will be removed in a future release. It may be set but is currently ignored.

"tls-data-size" (OSSL_MAC_PARAM_TLS_DATA_SIZE) <unsigned integer>
"key-check" (OSSL_MAC_PARAM_FIPS_KEY_CHECK) <integer>

See "Mac Parameters" in provider-mac(7).

The following parameters can be retrieved with EVP_MAC_CTX_get_params():

"size" (OSSL_MAC_PARAM_SIZE) <unsigned integer>

The "size" parameter can also be retrieved with EVP_MAC_CTX_get_mac_size(). The length of the "size" parameter is equal to that of an unsigned int.

"block-size" (OSSL_MAC_PARAM_BLOCK_SIZE) <unsigned integer>

Gets the MAC block size. The "block-size" parameter can also be retrieved with EVP_MAC_CTX_get_block_size().

"fips-indicator" (OSSL_MAC_PARAM_FIPS_APPROVED_INDICATOR) <integer>

See "Mac Parameters" in provider-mac(7).

Releases

3 releases since Debian 12 (Bookworm); the text changed 2 times.

  1. 12
  2. 13
  3. Arch

From openssl 3.6.5-1 in Arch Linux 2026-11-01. Parsed by carta from the page's man source.