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.\" -*- mode: troff; coding: utf-8 -*-
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.\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index
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.\" ========================================================================
.\"
.IX Title "EVP_PKEY-X25519 7SSL"
.TH EVP_PKEY-X25519 7SSL 2024-04-04 3.2.2-dev OpenSSL
.\" For nroff, turn off justification. Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH 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
\&\- EVP_PKEY X25519, X448, ED25519 and ED448 keytype and algorithm support
.SH DESCRIPTION
.IX Header "DESCRIPTION"
The \fBX25519\fR, \fBX448\fR, \fBED25519\fR and \fBED448\fR keytypes are
implemented in OpenSSL's default and FIPS providers. These implementations
support the associated key, containing the public key \fIpub\fR and the
private key \fIpriv\fR.
.SS "Keygen Parameters"
.IX Subsection "Keygen Parameters"
.IP """dhkem-ikm"" (\fBOSSL_PKEY_PARAM_DHKEM_IKM\fR) <octet string>" 4
.IX Item """dhkem-ikm"" (OSSL_PKEY_PARAM_DHKEM_IKM) <octet string>"
DHKEM requires the generation of a keypair using an input key material (seed).
Use this to specify the key material used for generation of the private key.
This value should not be reused for other purposes.
It should have a length of at least 32 for X25519, and 56 for X448.
.Sp
This is only supported by X25519 and X448.
.PP
Use \fBEVP_PKEY_CTX_set_params()\fR after calling \fBEVP_PKEY_keygen_init()\fR.
.SS "Common X25519, X448, ED25519 and ED448 parameters"
.IX Subsection "Common X25519, X448, ED25519 and ED448 parameters"
In addition to the common parameters that all keytypes should support (see
"Common parameters" in \fBprovider\-keymgmt\fR\|(7)), the implementation of these keytypes
support the following.
.IP """group"" (\fBOSSL_PKEY_PARAM_GROUP_NAME\fR) <UTF8 string>" 4
.IX Item """group"" (OSSL_PKEY_PARAM_GROUP_NAME) <UTF8 string>"
This is only supported by X25519 and X448. The group name must be "x25519" or
"x448" respectively for those algorithms. This is only present for consistency
with other key exchange algorithms and is typically not needed.
.IP """pub"" (\fBOSSL_PKEY_PARAM_PUB_KEY\fR) <octet string>" 4
.IX Item """pub"" (OSSL_PKEY_PARAM_PUB_KEY) <octet string>"
The public key value.
.IP """priv"" (\fBOSSL_PKEY_PARAM_PRIV_KEY\fR) <octet string>" 4
.IX Item """priv"" (OSSL_PKEY_PARAM_PRIV_KEY) <octet string>"
The private key value.
.IP """encoded-pub-key"" (\fBOSSL_PKEY_PARAM_ENCODED_PUBLIC_KEY\fR) <octet string>" 4
.IX Item """encoded-pub-key"" (OSSL_PKEY_PARAM_ENCODED_PUBLIC_KEY) <octet string>"
Used for getting and setting the encoding of a public key for the \fBX25519\fR and
\&\fBX448\fR key types. Public keys are expected be encoded in a format as defined by
RFC7748.
.SS "ED25519 and ED448 parameters"
.IX Subsection "ED25519 and ED448 parameters"
.IP """mandatory-digest"" (\fBOSSL_PKEY_PARAM_MANDATORY_DIGEST\fR) <UTF8 string>" 4
.IX Item """mandatory-digest"" (OSSL_PKEY_PARAM_MANDATORY_DIGEST) <UTF8 string>"
The empty string, signifying that no digest may be specified.
.SH "CONFORMING TO"
.IX Header "CONFORMING TO"
.IP "RFC 8032" 4
.IX Item "RFC 8032"
.PD 0
.IP "RFC 8410" 4
.IX Item "RFC 8410"
.PD
.SH EXAMPLES
.IX Header "EXAMPLES"
An \fBEVP_PKEY\fR context can be obtained by calling:
.PP
.Vb 2
\& 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);
.Ve
.PP
An \fBX25519\fR key can be generated like this:
.PP
.Vb 1
\& pkey = EVP_PKEY_Q_keygen(NULL, NULL, "X25519");
.Ve
.PP
An \fBX448\fR, \fBED25519\fR, or \fBED448\fR key can be generated likewise.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBEVP_KEYMGMT\fR\|(3), \fBEVP_PKEY\fR\|(3), \fBprovider\-keymgmt\fR\|(7),
\&\fBEVP_KEYEXCH\-X25519\fR\|(7), \fBEVP_KEYEXCH\-X448\fR\|(7),
\&\fBEVP_SIGNATURE\-ED25519\fR\|(7), \fBEVP_SIGNATURE\-ED448\fR\|(7)
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright 2020\-2021 The OpenSSL Project Authors. All Rights Reserved.
.PP
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>.
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