1=pod 2 3=head1 NAME 4 5EVP_PKEY_set1_encoded_public_key, EVP_PKEY_get1_encoded_public_key, 6EVP_PKEY_set1_tls_encodedpoint, EVP_PKEY_get1_tls_encodedpoint 7- functions to set and get public key data within an EVP_PKEY 8 9=head1 SYNOPSIS 10 11 #include <openssl/evp.h> 12 13 int EVP_PKEY_set1_encoded_public_key(EVP_PKEY *pkey, 14 const unsigned char *pub, size_t publen); 15 16 size_t EVP_PKEY_get1_encoded_public_key(EVP_PKEY *pkey, unsigned char **ppub); 17 18The following functions have been deprecated since OpenSSL 3.0, and can be 19hidden entirely by defining B<OPENSSL_API_COMPAT> with a suitable version value, 20see L<openssl_user_macros(7)>: 21 22 int EVP_PKEY_set1_tls_encodedpoint(EVP_PKEY *pkey, 23 const unsigned char *pt, size_t ptlen); 24 25 size_t EVP_PKEY_get1_tls_encodedpoint(EVP_PKEY *pkey, unsigned char **ppt); 26 27=head1 DESCRIPTION 28 29EVP_PKEY_set1_encoded_public_key() can be used to set the public key value 30within an existing EVP_PKEY object, which does not yet have either a public or 31private key assigned. 32For the built-in OpenSSL algorithms this currently only works for those that 33support key exchange or key encapsulation. 34Parameters are not set as part of this operation, so typically an application 35will create an EVP_PKEY first, set the parameters on it, and then call this 36function. 37For example setting the parameters might be done using 38L<EVP_PKEY_copy_parameters(3)>. 39 40The format for the encoded public key will depend on the algorithm in use. For 41DH it should be encoded as a positive integer in big-endian form. For EC is 42should be a point conforming to Sec. 2.3.4 of the SECG SEC 1 ("Elliptic 43Curve Cryptography") standard. For B<X25519> and B<X448> it should be encoded 44in the format defined by RFC7748. 45For B<ML-KEM-512>, B<ML-KEM-768> and B<ML-KEM-1024>, this is the public key 46format defined in B<FIPS 203> (the 12-bit per-coefficient encoded public I<t> 47vector and 32-byte matrix seed I<rho>). 48 49The key to be updated is supplied in B<pkey>. The buffer containing the encoded 50key is pointed to be B<pub>. The length of the buffer is supplied in B<publen>. 51 52EVP_PKEY_get1_encoded_public_key() does the equivalent operation except that 53the encoded public key is returned to the application. The key containing the 54public key data is supplied in B<pkey>. A buffer containing the encoded key will 55be allocated and stored in B<*ppub>. The length of the encoded public key is 56returned by the function. The application is responsible for freeing the 57allocated buffer. 58 59The macro EVP_PKEY_set1_tls_encodedpoint() is deprecated and simply calls 60EVP_PKEY_set1_encoded_public_key() with all the same arguments. New applications 61should use EVP_PKEY_set1_encoded_public_key() instead. 62 63The macro EVP_PKEY_get1_tls_encodedpoint() is deprecated and simply calls 64EVP_PKEY_get1_encoded_public_key() with all the same arguments. New applications 65should use EVP_PKEY_get1_encoded_public_key() instead. 66 67 68=head1 RETURN VALUES 69 70EVP_PKEY_set1_encoded_public_key() returns 1 for success and 0 or a negative 71value for failure. 72 73EVP_PKEY_get1_encoded_public_key() returns the length of the encoded key or 0 for failure. 74 75=head1 EXAMPLES 76 77See L<EVP_PKEY_derive_init(3)> and L<EVP_PKEY_derive(3)> for information about 78performing a key exchange operation. 79 80=head2 Set up a peer's EVP_PKEY ready for a key exchange operation 81 82 #include <openssl/evp.h> 83 84 int exchange(EVP_PKEY *ourkey, unsigned char *peer_pub, size_t peer_pub_len) 85 { 86 EVP_PKEY *peerkey = EVP_PKEY_new(); 87 88 if (peerkey == NULL || EVP_PKEY_copy_parameters(peerkey, ourkey) <= 0) 89 return 0; 90 91 if (EVP_PKEY_set1_encoded_public_key(peerkey, peer_pub, 92 peer_pub_len) <= 0) 93 return 0; 94 95 /* Do the key exchange here */ 96 97 EVP_PKEY_free(peerkey); 98 99 return 1; 100 } 101 102=head2 Get an encoded public key to send to a peer 103 104 #include <openssl/evp.h> 105 106 int get_encoded_pub_key(EVP_PKEY *ourkey) 107 { 108 unsigned char *pubkey; 109 size_t pubkey_len; 110 111 pubkey_len = EVP_PKEY_get1_encoded_public_key(ourkey, &pubkey); 112 if (pubkey_len == 0) 113 return 0; 114 115 /* 116 * Send the encoded public key stored in the buffer at "pubkey" and of 117 * length pubkey_len, to the peer. 118 */ 119 120 OPENSSL_free(pubkey); 121 return 1; 122 } 123 124=head1 SEE ALSO 125 126L<EVP_PKEY_new(3)>, 127L<EVP_PKEY_copy_parameters(3)>, 128L<EVP_PKEY_derive_init(3)>, 129L<EVP_PKEY_derive(3)>, 130L<EVP_PKEY-DH(7)>, 131L<EVP_PKEY-EC(7)>, 132L<EVP_PKEY-X25519(7)>, 133L<EVP_PKEY-X448(7)>, 134L<EVP_PKEY-ML-KEM-512(7)>, 135L<EVP_PKEY-ML-KEM-768(7)>, 136L<EVP_PKEY-ML-KEM-1024(7)>. 137 138=head1 HISTORY 139 140EVP_PKEY_set1_encoded_public_key() and EVP_PKEY_get1_encoded_public_key() were 141added in OpenSSL 3.0. 142 143EVP_PKEY_set1_tls_encodedpoint() and EVP_PKEY_get1_tls_encodedpoint() were 144deprecated in OpenSSL 3.0. 145 146Support for B<ML-KEM> was added in OpenSSL 3.5. 147 148=head1 COPYRIGHT 149 150Copyright 2020-2025 The OpenSSL Project Authors. All Rights Reserved. 151 152Licensed under the Apache License 2.0 (the "License"). You may not use 153this file except in compliance with the License. You can obtain a copy 154in the file LICENSE in the source distribution or at 155L<https://www.openssl.org/source/license.html>. 156 157=cut 158 159