1X25519(7)                           OpenSSL                          X25519(7)
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NAME

6       X25519, X448 - EVP_PKEY X25519 and X448 support
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DESCRIPTION

9       The X25519 and X448 EVP_PKEY implementation supports key generation and
10       key derivation using X25519 and X448. It has associated private and
11       public key formats compatible with draft-ietf-curdle-pkix-03.
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13       No additional parameters can be set during key generation.
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15       The peer public key must be set using EVP_PKEY_derive_set_peer() when
16       performing key derivation.
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NOTES

19       A context for the X25519 algorithm can be obtained by calling:
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21        EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_X25519, NULL);
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23       For the X448 algorithm a context can be obtained by calling:
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25        EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_X448, NULL);
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27       X25519 or X448 private keys can be set directly using
28       EVP_PKEY_new_raw_private_key(3) or loaded from a PKCS#8 private key
29       file using PEM_read_bio_PrivateKey(3) (or similar function). Completely
30       new keys can also be generated (see the example below). Setting a
31       private key also sets the associated public key.
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33       X25519 or X448 public keys can be set directly using
34       EVP_PKEY_new_raw_public_key(3) or loaded from a SubjectPublicKeyInfo
35       structure in a PEM file using PEM_read_bio_PUBKEY(3) (or similar
36       function).
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EXAMPLES

39       This example generates an X25519 private key and writes it to standard
40       output in PEM format:
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42        #include <openssl/evp.h>
43        #include <openssl/pem.h>
44        ...
45        EVP_PKEY *pkey = NULL;
46        EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_X25519, NULL);
47        EVP_PKEY_keygen_init(pctx);
48        EVP_PKEY_keygen(pctx, &pkey);
49        EVP_PKEY_CTX_free(pctx);
50        PEM_write_PrivateKey(stdout, pkey, NULL, NULL, 0, NULL, NULL);
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52       The key derivation example in EVP_PKEY_derive(3) can be used with
53       X25519 and X448.
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SEE ALSO

56       EVP_PKEY_CTX_new(3), EVP_PKEY_keygen(3), EVP_PKEY_derive(3),
57       EVP_PKEY_derive_set_peer(3)
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60       Copyright 2017-2019 The OpenSSL Project Authors. All Rights Reserved.
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62       Licensed under the OpenSSL license (the "License").  You may not use
63       this file except in compliance with the License.  You can obtain a copy
64       in the file LICENSE in the source distribution or at
65       <https://www.openssl.org/source/license.html>.
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691.1.1d                            2019-10-03                         X25519(7)
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