=pod

=head1 NAME

EVP_SIGNATURE-ED25519,
EVP_SIGNATURE-ED448,
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
RFC 8410.

No additional parameters can be set during one-shot signing or verification.
In particular, because PureEdDSA is used, a digest must B<NOT> be specified when
signing or verifying.
See L<EVP_PKEY-X25519(7)> for information related to B<X25519> and B<X448> keys.

=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() and EVP_DigestVerify() functions.

When calling EVP_DigestSignInit() or EVP_DigestVerifyInit(), the
digest I<type> parameter B<MUST> be set to 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.

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).

Ed25519 and Ed448 can be tested with the L<openssl-speed(1)> application
since version 1.1.1.
Valid algorithm names are B<ed25519>, B<ed448> and B<eddsa>. If B<eddsa> is
specified, then both Ed25519 and Ed448 are benchmarked.

=head1 EXAMPLES

To sign a message using a ED25519 or ED448 key:

    void do_sign(EVP_PKEY *ed_key, unsigned char *msg, size_t msg_len)
    {
        size_t sig_len;
        unsigned char *sig = NULL;
        EVP_MD_CTX *md_ctx = EVP_MD_CTX_new();

        EVP_DigestSignInit(md_ctx, NULL, NULL, NULL, ed_key);
        /* Calculate the requires size for the signature by passing a NULL buffer */
        EVP_DigestSign(md_ctx, NULL, &sig_len, msg, msg_len);
        sig = OPENSSL_zalloc(sig_len);

        EVP_DigestSign(md_ctx, sig, &sig_len, msg, msg_len);
        ...
        OPENSSL_free(sig);
        EVP_MD_CTX_free(md_ctx);
    }

=head1 SEE ALSO

L<EVP_PKEY-X25519(7)>
L<provider-signature(7)>,
L<EVP_DigestSignInit(3)>,
L<EVP_DigestVerifyInit(3)>,

=head1 COPYRIGHT

Copyright 2017-2020 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
L<https://www.openssl.org/source/license.html>.

=cut