1=pod 2 3=head1 NAME 4 5EVP_PKEY_CTX_new, EVP_PKEY_CTX_new_id, EVP_PKEY_CTX_new_from_name, 6EVP_PKEY_CTX_new_from_pkey, EVP_PKEY_CTX_dup, EVP_PKEY_CTX_free, 7EVP_PKEY_CTX_is_a 8- public key algorithm context functions 9 10=head1 SYNOPSIS 11 12 #include <openssl/evp.h> 13 14 EVP_PKEY_CTX *EVP_PKEY_CTX_new(EVP_PKEY *pkey, ENGINE *e); 15 EVP_PKEY_CTX *EVP_PKEY_CTX_new_id(int id, ENGINE *e); 16 EVP_PKEY_CTX *EVP_PKEY_CTX_new_from_name(OSSL_LIB_CTX *libctx, 17 const char *name, 18 const char *propquery); 19 EVP_PKEY_CTX *EVP_PKEY_CTX_new_from_pkey(OSSL_LIB_CTX *libctx, 20 EVP_PKEY *pkey, 21 const char *propquery); 22 EVP_PKEY_CTX *EVP_PKEY_CTX_dup(const EVP_PKEY_CTX *ctx); 23 void EVP_PKEY_CTX_free(EVP_PKEY_CTX *ctx); 24 int EVP_PKEY_CTX_is_a(EVP_PKEY_CTX *ctx, const char *keytype); 25 26=head1 DESCRIPTION 27 28The EVP_PKEY_CTX_new() function allocates public key algorithm context using 29the I<pkey> key type and ENGINE I<e>. 30 31The EVP_PKEY_CTX_new_id() function allocates public key algorithm context 32using the key type specified by I<id> and ENGINE I<e>. 33 34The EVP_PKEY_CTX_new_from_name() function allocates a public key algorithm 35context using the library context I<libctx> (see L<OSSL_LIB_CTX(3)>), the 36key type specified by I<name> and the property query I<propquery>. None 37of the arguments are duplicated, so they must remain unchanged for the 38lifetime of the returned B<EVP_PKEY_CTX> or of any of its duplicates. Read 39further about the possible names in L</NOTES> below. 40 41The EVP_PKEY_CTX_new_from_pkey() function allocates a public key algorithm 42context using the library context I<libctx> (see L<OSSL_LIB_CTX(3)>) and the 43algorithm specified by I<pkey> and the property query I<propquery>. None of the 44arguments are duplicated, so they must remain unchanged for the lifetime of the 45returned B<EVP_PKEY_CTX> or any of its duplicates. 46 47EVP_PKEY_CTX_new_id() and EVP_PKEY_CTX_new_from_name() are normally 48used when no B<EVP_PKEY> structure is associated with the operations, 49for example during parameter generation or key generation for some 50algorithms. 51 52EVP_PKEY_CTX_dup() duplicates the context I<ctx>. It is not supported for a 53keygen operation. 54 55EVP_PKEY_CTX_free() frees up the context I<ctx>. 56If I<ctx> is NULL, nothing is done. 57 58EVP_PKEY_is_a() checks if the key type associated with I<ctx> is I<keytype>. 59 60=head1 NOTES 61 62=head2 On B<EVP_PKEY_CTX> 63 64The B<EVP_PKEY_CTX> structure is an opaque public key algorithm context used 65by the OpenSSL high-level public key API. Contexts B<MUST NOT> be shared between 66threads: that is it is not permissible to use the same context simultaneously 67in two threads. 68 69=head2 On Key Types 70 71We mention "key type" in this manual, which is the same 72as "algorithm" in most cases, allowing either term to be used 73interchangeably. There are algorithms where the I<key type> and the 74I<algorithm> of the operations that use the keys are not the same, 75such as EC keys being used for ECDSA and ECDH operations. 76 77Key types are given in two different manners: 78 79=over 4 80 81=item Legacy NID or EVP_PKEY type 82 83This is the I<id> used with EVP_PKEY_CTX_new_id(). 84 85These are B<EVP_PKEY_RSA>, B<EVP_PKEY_RSA_PSS>, B<EVP_PKEY_DSA>, 86B<EVP_PKEY_DH>, B<EVP_PKEY_EC>, B<EVP_PKEY_SM2>, B<EVP_PKEY_X25519>, 87B<EVP_PKEY_X448>, and are used by legacy methods. 88 89=item Name strings 90 91This is the I<name> used with EVP_PKEY_CTX_new_from_name(). 92 93These are names like "RSA", "DSA", and what's available depends on what 94providers are currently accessible. 95 96The OpenSSL providers offer a set of key types available this way, please 97see L<OSSL_PROVIDER-FIPS(7)> and L<OSSL_PROVIDER-default(7)> and related 98documentation for more information. 99 100=back 101 102=head1 RETURN VALUES 103 104EVP_PKEY_CTX_new(), EVP_PKEY_CTX_new_id() and EVP_PKEY_CTX_dup() return either 105the newly allocated B<EVP_PKEY_CTX> structure or B<NULL> if an error occurred. 106 107EVP_PKEY_CTX_free() does not return a value. 108 109EVP_PKEY_CTX_is_a() returns 1 for true and 0 for false. 110 111=head1 SEE ALSO 112 113L<EVP_PKEY_new(3)> 114 115=head1 HISTORY 116 117The EVP_PKEY_CTX_new(), EVP_PKEY_CTX_new_id(), EVP_PKEY_CTX_dup() and 118EVP_PKEY_CTX_free() functions were added in OpenSSL 1.0.0. 119 120The EVP_PKEY_CTX_new_from_name() and EVP_PKEY_CTX_new_from_pkey() functions were 121added in OpenSSL 3.0. 122 123=head1 COPYRIGHT 124 125Copyright 2006-2021 The OpenSSL Project Authors. All Rights Reserved. 126 127Licensed under the Apache License 2.0 (the "License"). You may not use 128this file except in compliance with the License. You can obtain a copy 129in the file LICENSE in the source distribution or at 130L<https://www.openssl.org/source/license.html>. 131 132=cut 133