EVP_PKEY-X25519(7SSL)

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version 4.0.3 · 13 versions
, in ubuntu stonking

💖 EVP_PKEY-X25519(7SSL) 💖

okay bestie, gather round, because today we're talking about the OpenSSL manual page EVP_PKEY-X25519(7SSL) and it's literally the whole glow-up guide for four absolute icons: X25519, X448, ED25519 and ED448. 🦋

✨ NAME ✨

EVP_PKEY-X25519, EVP_PKEY-X448, EVP_PKEY-ED25519, EVP_PKEY-ED448, EVP_KEYMGMT-X25519, EVP_KEYMGMT-X448, EVP_KEYMGMT-ED25519, EVP_KEYMGMT-ED448 — this is the keytype + algorithm support page for X25519, X448, ED25519 and ED448. no cap. 🔥

🌸 DESCRIPTION 🌸

So here's the tea: the X25519, X448, ED25519 and ED448 keytypes are implemented in OpenSSL's default and FIPS providers. These implementations support the associated key, and that key is carrying two things:

  • the public key pub 💅
  • the private key priv 🙈

🎀 Common Keygen Parameters for X25519, X448, ED25519 and ED448 🎀

You can use these parameters during key generation by calling EVP_PKEY_CTX_set_params() after calling EVP_PKEY_keygen_init(). yes you must do them in that order, the sequence is the moment, periodt.

  • "properties" (OSSL_PKEY_PARAM_PROPERTIES) <octet string> — the property query to use when fetching algorithms during the key generation operation. it's giving "who am I allowed to pull up while I'm doing this keygen". ✨

👑 Keygen Parameters for X25519 and X448 👑

  • "dhkem-ikm" (OSSL_PKEY_PARAM_DHKEM_IKM) <octet string> — DHKEM requires the generation of a keypair using an input key material (a.k.a. a seed). use this to specify the key material used for generation of the private key. > ⚠️ this value should not be reused for other purposes. not me saying this twice but fr fr do not recycle it. and it should have a length of at least 32 for X25519, and 56 for X448.
  • "group" (OSSL_PKEY_PARAM_GROUP_NAME) <UTF8 string> — the group name must be "x25519" or "x448" respectively for those algorithms. lowkey this is only present for consistency with other key exchange algorithms and is typically not needed. it's just there to match the vibe of the rest of the family. 🫶

🌈 Common Parameters for X25519, X448, ED25519 and ED448 🌈

On top of the common parameters that all keytypes should support (peep "Common parameters" in provider-keymgmt(7)), the implementation of these keytypes also supports the following:

  • "pub" (OSSL_PKEY_PARAM_PUB_KEY) <octet string> — the public key value. the one you share with the world. main character energy. ✨
  • "priv" (OSSL_PKEY_PARAM_PRIV_KEY) <octet string> — the private key value. the one you keep in the group chat you don't talk about. 🤫

💜 Parameters for X25519 and X448 💜

  • "encoded-pub-key" (OSSL_PKEY_PARAM_ENCODED_PUBLIC_KEY) <octet string> — used for getting and setting the encoding of a public key for the X25519 and X448 key types. public keys are expected be encoded in a format as defined by RFC7748.
  • "fips-indicator" (OSSL_PKEY_PARAM_FIPS_APPROVED_INDICATOR) <integer> — this getter is only supported by X25519 and X448 OpenSSL FIPS provider. and since X25519 and X448 are unapproved in FIPS 140-3, this getter returns 0. that's the whole answer. zero. 💀 (not a bad zero, just... the honest zero.)

🦋 Parameters for ED25519 and ED448 🦋

  • "mandatory-digest" (OSSL_PKEY_PARAM_MANDATORY_DIGEST) <UTF8 string> — the empty string, signifying that no digest may be specified. like, the string is empty and that emptiness is the point. iconic. 🎀

⭐ CONFORMING TO ⭐

she conforms. obviously. 👑

💅 EXAMPLES 💅

An EVP_PKEY context can be obtained by calling:

EVP_PKEY_CTX *pctx =
    EVP_PKEY_CTX_new_from_name(NULL, "X25519", NULL);

EVP_PKEY_CTX *pctx =
    EVP_PKEY_CTX_new_from_name(NULL, "X448", NULL);

EVP_PKEY_CTX *pctx =
    EVP_PKEY_CTX_new_from_name(NULL, "ED25519", NULL);

EVP_PKEY_CTX *pctx =
    EVP_PKEY_CTX_new_from_name(NULL, "ED448", NULL);

An X25519 key can be generated like this:

pkey = EVP_PKEY_Q_keygen(NULL, NULL, "X25519");

An X448, ED25519, or ED448 key can be generated likewise. same energy, different name, you just swap the string. slay. 🐛✨

🌸 SEE ALSO 🌸

EVP_KEYMGMT(3), EVP_PKEY(3), provider-keymgmt(7), EVP_KEYEXCH-X25519(7), EVP_KEYEXCH-X448(7), EVP_SIGNATURE-ED25519(7), EVP_SIGNATURE-ED448(7)

go read those too, bestie, they're all in the same friend group. 🫶

Copyright 2020-2025 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>.

and that's the whole page, no crumbs left. this lil masterpiece is from OpenSSL version 4.0.3, dated 2026-09-29, and it lives under the manual name EVP_PKEY-X25519(7SSL). bye bestie, go generate some keys responsibly 💖🌈⭐

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