EVP_MAC-GMAC(7SSL)

📦
version 4.0.3 · 13 versions
, in ubuntu stonking

💖 EVP_MAC-GMAC 💖

okay so bestie, welcome to the manual page for EVP_MAC-GMAC, straight outta the OpenSSL docs 📖✨ — this is the GMAC EVP_MAC implementation, and we're gonna get you acquainted, no cap.

✨ NAME ✨

EVP_MAC-GMAC — the GMAC EVP_MAC implementation. that's it, that's the name, she's literally that girl 💅

🌸 DESCRIPTION 🌸

This bad girl provides support for computing GMAC MACs through the EVP_MAC API. periodt.

And the way she does it? This implementation uses EVP_CIPHER functions to get access to the underlying cipher. iconic behavior fr fr 🔥

🎀 Identity 🎀

This implementation gets identified by this name and these properties, and you use them with EVP_MAC_fetch():

  • "GMAC", "provider=default" or "provider=fips" 🌈

🦋 Supported parameters 🦋

The general description of these parameters lives in "PARAMETERS" in EVP_MAC(3) — go peek if you want the full lore, iykyk.

The following parameter 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).
  • "iv" (OSSL_MAC_PARAM_IV) <octet string> — sets the IV of the underlying cipher, when applicable.
  • "cipher" (OSSL_MAC_PARAM_CIPHER) <UTF8 string> — sets the name of the underlying cipher to be used.
  • "properties" (OSSL_MAC_PARAM_PROPERTIES) <UTF8 string> — sets the properties to be queried when trying to fetch the underlying cipher. 🫶 This one must be given together with the cipher naming parameter to be considered valid, so don't be out here giving properties all alone, bestie, it's giving invalid 😭

The following parameters can be retrieved with EVP_MAC_CTX_get_params():

  • "size" (OSSL_MAC_PARAM_SIZE) <unsigned integer> — gets the MAC size.
  • "fips-indicator" (OSSL_MAC_PARAM_FIPS_APPROVED_INDICATOR) <integer> — the OpenSSL FIPS provider returns 1 if the operation is FIPS approved, or 0 otherwise. See "FIPS indicators" in fips_module(7) for more information. 👑

okay and listen, the "size" parameter can also be retrieved with EVP_MAC_CTX_get_mac_size(). ✨ And the length of the "size" parameter is equal to that of an unsigned int. cute, consistent, we love a matching set 💜

💫 SEE ALSO 💫

go read those too, bestie, they're the supporting cast 🌟

Copyright 2018-2026 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>. 📜✨

aaand that's the whole page, you ate that 🍓 this was version 4.0.3, dated 2026-09-29, and she's the EVP_MAC-GMAC(7SSL) manual — mwah, take care, love u, bye 💖🎀🦋

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