NAME

       X25519, X448 - EVP_PKEY X25519 and X448 support

DESCRIPTION

       The X25519 and X448 EVP_PKEY implementation supports key generation and key derivation
       using X25519 and X448. It has associated private and public key formats compatible with
       draft-ietf-curdle-pkix-03.

       No additional parameters can be set during key generation.

       The peer public key must be set using EVP_PKEY_derive_set_peer() when performing key
       derivation.

NOTES

       A context for the X25519 algorithm can be obtained by calling:

        EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_X25519, NULL);

       For the X448 algorithm a context can be obtained by calling:

        EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_X448, NULL);

       X25519 or X448 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.

       X25519 or X448 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).

EXAMPLE

       This example generates an X25519 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_X25519, 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);

       The key derivation example in EVP_PKEY_derive(3) can be used with X25519 and X448.

SEE ALSO

       EVP_PKEY_CTX_new(3), EVP_PKEY_keygen(3), EVP_PKEY_derive(3), EVP_PKEY_derive_set_peer(3)

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 <https://www.openssl.org/source/license.html>.