- NAME
- DESCRIPTION
  - ED25519 and ED448 Signature Parameters
- NOTES
- EXAMPLES
- SEE ALSO
- COPYRIGHT

# NAME

EVP_SIGNATURE-ED25519, EVP_SIGNATURE-ED448, Ed25519, Ed448 - EVP_PKEY Ed25519 and Ed448 support

# DESCRIPTION

The Ed25519 and Ed448 EVP_PKEY implementation supports key generation, one-shot digest sign and digest verify using PureEdDSA and Ed25519 or Ed448 (see RFC8032). It has associated private and public key formats compatible with RFC 8410.

## ED25519 and ED448 Signature Parameters

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

The following signature parameters can be retrieved using EVP_PKEY_CTX_get_params().

"algorithm-id" (OSSL_SIGNATURE_PARAM_ALGORITHM_ID) <octet string>

  The parameters are described in provider-signature(7).

# 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 type parameter 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 EVP_PKEY_new_raw_private_key(3) or loaded from a PKCS#8 private key file using 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 EVP_PKEY_new_raw_public_key(3) or loaded from a SubjectPublicKeyInfo structure in a PEM file using PEM_read_bio_PUBKEY(3) (or similar function).

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

# 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);
    }

# SEE ALSO

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

# COPYRIGHT

Copyright 2017-2021 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.