EVP_MD-SHAKE(7ssl)

📦
version 3.6.5 · 11 versions
, in arch rolling

💖 NAME 💖

okay so this is the EVP_MD-SHAKE / EVP_MD-KECCAK-KMAC girlies — they're the SHAKE / KECCAK family EVP_MD implementations, and this page is literally all about them. (also hi, you're reading the 7ssl manual, bestie 🫶)

✨ DESCRIPTION ✨

So basically this whole thing is about computing SHAKE or KECCAK-KMAC digests through the EVP_MD API. no cap. 🌸

KECCAK-KMAC is an Extendable Output Function (XOF), and its definition is similar to SHAKE. It's the one used by the KMAC EVP_MAC implementation (peep EVP_MAC-KMAC(7) if you wanna go deeper 👀).

🦋 Identities 🦋

This implementation is available in the FIPS provider as well as the default provider, and it includes the following varieties. the way there are so many of them?? obsessed 💅

  • KECCAK-KMAC-128 — the known names are "KECCAK-KMAC-128" and "KECCAK-KMAC128". This one is used by EVP_MAC-KMAC128(7). Using the notation from NIST FIPS 202 (Section 6.2), we have KECCAK-KMAC-128(M, d) = KECCAK[256](M || 00, d) (see the description of KMAC128 in Appendix A of NIST SP 800-185). ✨
  • KECCAK-KMAC-256 — known names are "KECCAK-KMAC-256" and "KECCAK-KMAC256". This one is used by EVP_MAC-KMAC256(7). Using the notation from NIST FIPS 202 (Section 6.2), we have KECCAK-KMAC-256(M, d) = KECCAK[512](M || 00, d) (see the description of KMAC256 in Appendix A of NIST SP 800-185). 💜
  • SHAKE-128 — known names are "SHAKE-128" and "SHAKE128". 🌈
  • SHAKE-256 — known names are "SHAKE-256" and "SHAKE256". 🌈

🎀 Parameters 🎀

This implementation supports the following OSSL_PARAM(3) entries, bestie, write these down 📝:

  • "xoflen" (OSSL_DIGEST_PARAM_XOFLEN) <unsigned integer> — Sets or Gets the digest length for extendable output functions. The length of the "xoflen" parameter should not exceed that of a size_t.

The SHAKE-128 and SHAKE-256 implementations do not have any default digest length. 😭

This parameter must be set before calling either EVP_DigestFinal_ex() or EVP_DigestFinal(), since these functions were not designed to handle variable length output. It is recommended to either use EVP_DigestSqueeze() or EVP_DigestFinalXOF() instead. fr fr, listen to the docs on this one.
  • "size" (OSSL_DIGEST_PARAM_SIZE) <unsigned integer> — an alias of "xoflen". same energy, different name 💅

See "PARAMETERS" in EVP_DigestInit(3) for further information related to parameters.

📌 NOTES 📌

  • For SHAKE-128, to ensure the maximum security strength of 128 bits, the output length passed to EVP_DigestFinalXOF() should be at least 32. 🔥
  • For SHAKE-256, to ensure the maximum security strength of 256 bits, the output length passed to EVP_DigestFinalXOF() should be at least 64. 🔥

👀 SEE ALSO 👀

⭐ HISTORY ⭐

Since OpenSSL 3.4 the SHAKE-128 and SHAKE-256 implementations have no default digest length. (the glow up was real 💅)

Copyright 2020-2024 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>.

okay that's the whole page, you ate it 🫶 this was OpenSSL version 3.6.5, dated 2026-09-29, signing off bestie, mwah 💖✨

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