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=head1 NAME

EVP_PKEY_param_fromdata_init, EVP_PKEY_key_fromdata_init, EVP_PKEY_fromdata,
EVP_PKEY_param_fromdata_settable, EVP_PKEY_key_fromdata_settable
- functions to create key parameters and keys from user data

=head1 SYNOPSIS

 #include <openssl/evp.h>

 int EVP_PKEY_param_fromdata_init(EVP_PKEY_CTX *ctx);
 int EVP_PKEY_key_fromdata_init(EVP_PKEY_CTX *ctx);
 int EVP_PKEY_fromdata(EVP_PKEY_CTX *ctx, EVP_PKEY **ppkey, OSSL_PARAM params[]);
 const OSSL_PARAM *EVP_PKEY_param_fromdata_settable(EVP_PKEY_CTX *ctx);
 const OSSL_PARAM *EVP_PKEY_key_fromdata_settable(EVP_PKEY_CTX *ctx);

=head1 DESCRIPTION

EVP_PKEY_param_fromdata_init() initializes a public key algorithm context
for creating key parameters from user data.

EVP_PKEY_key_fromdata_init() initializes a public key algorithm context for
creating a key from user data.

EVP_PKEY_fromdata() creates key parameters or a key, given data from
I<params> and a context that's been initialized with
EVP_PKEY_param_fromdata_init() or EVP_PKEY_key_fromdata_init().  The result is
written to I<*ppkey>. The parameters that can be used for various types of key
are as described in the "Built-in RSA Import/Export Types" section on the
L<provider-keymgmt(7)> page.

EVP_PKEY_param_fromdata_settable() and EVP_PKEY_key_fromdata_settable()
get a constant B<OSSL_PARAM> array that describes the settable parameters
that can be used with EVP_PKEY_fromdata().
See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as parameter descriptor.

=head1 NOTES

These functions only work with key management methods coming from a
provider.

=for comment We may choose to make this available for legacy methods too... 

=head1 RETURN VALUES

EVP_PKEY_key_fromdata_init(), EVP_PKEY_param_fromdata_init() and
EVP_PKEY_fromdata() return 1 for success and 0 or a negative value for
failure.  In particular a return value of -2 indicates the operation is
not supported by the public key algorithm.

=head1 SEE ALSO

L<EVP_PKEY_CTX_new(3)>, L<provider(7)>, L<EVP_PKEY_gettable_params(3)>

=head1 HISTORY

These functions were added in OpenSSL 3.0.

=head1 COPYRIGHT

Copyright 2019 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
L<https://www.openssl.org/source/license.html>.

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