=pod

=head1 NAME

Ed25519,
Ed448
- EVP_PKEY Ed25519 and Ed448 support

=head1 DESCRIPTION

The B<Ed25519> and B<Ed448> EVP_PKEY implementation supports key generation,
one-shot digest sign and digest verify using PureEdDSA and B<Ed25519> or B<Ed448>
(see RFC8032). It has associated private and public key formats compatible with
draft-ietf-curdle-pkix-04.

No additional parameters can be set during key generation one-shot signing or
verification. In particular, because PureEdDSA is used, when signing or
verifying a digest must B<NOT> be specified.

=head1 NOTES

The PureEdDSA algorithm does not support the streaming mechanism
of other signature algorithms using, for example, EVP_DigestUpdate().
The message to sign or verify must be passed using the one-shot
EVP_DigestSign() asn EVP_DigestVerify() functions.

When calling EVP_DigestSignInit() or EVP_DigestSignUpdate() the
digest parameter B<MUST> be set to B<NULL>.

Applications wishing to sign certificates (or other structures such as
CRLs or certificate requests) using Ed25519 or Ed448 can either use X509_sign()
or X509_sign_ctx() in the usual way.

A context for the B<Ed25519> algorithm can be obtained by calling:

 EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_ED25519, NULL);

For the B<Ed448> algorithm a context can be obtained by calling:

 EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_ED448, NULL);

Ed25519 or Ed448 private keys can be set directly using
L<EVP_PKEY_new_raw_private_key(3)> or loaded from a PKCS#8 private key file
using L<PEM_read_bio_PrivateKey(3)> (or similar function). Completely new keys
can also be generated (see the example below). Setting a private key also sets
the associated public key.

Ed25519 or Ed448 public keys can be set directly using
L<EVP_PKEY_new_raw_public_key(3)> or loaded from a SubjectPublicKeyInfo
structure in a PEM file using L<PEM_read_bio_PUBKEY(3)> (or similar function).

=head1 EXAMPLE

This example generates an B<ED25519> private key and writes it to standard
output in PEM format:

 #include <openssl/evp.h>
 #include <openssl/pem.h>
 ...
 EVP_PKEY *pkey = NULL;
 EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_ED25519, NULL);
 EVP_PKEY_keygen_init(pctx);
 EVP_PKEY_keygen(pctx, &pkey);
 EVP_PKEY_CTX_free(pctx);
 PEM_write_PrivateKey(stdout, pkey, NULL, NULL, 0, NULL, NULL);

=head1 SEE ALSO

L<EVP_PKEY_CTX_new(3)>,
L<EVP_PKEY_keygen(3)>,
L<EVP_DigestSignInit(3)>,
L<EVP_DigestVerifyInit(3)>,

=head1 COPYRIGHT

Copyright 2017-2018 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (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
L<https://www.openssl.org/source/license.html>.

=cut
