=pod

=head1 NAME

EVP_PKEY_encrypt_init_ex, 
EVP_PKEY_encrypt_init, EVP_PKEY_encrypt - encrypt using a public key algorithm

=head1 SYNOPSIS

 #include <openssl/evp.h>

 int EVP_PKEY_encrypt_init(EVP_PKEY_CTX *ctx);
 int EVP_PKEY_encrypt_init_ex(EVP_PKEY_CTX *ctx, const OSSL_PARAM params[]);
 int EVP_PKEY_encrypt(EVP_PKEY_CTX *ctx,
                      unsigned char *out, size_t *outlen,
                      const unsigned char *in, size_t inlen);

=head1 DESCRIPTION

The EVP_PKEY_encrypt_init() function initializes a public key algorithm
context using key B<pkey> for an encryption operation.

The EVP_PKEY_encrypt_init_ex() function initializes a public key algorithm
context using key B<pkey> for an encryption operation and sets the
algorithm specific B<params>.

The EVP_PKEY_encrypt() function performs a public key encryption operation
using B<ctx>. The data to be encrypted is specified using the B<in> and
B<inlen> parameters. If B<out> is B<NULL> then the maximum size of the output
buffer is written to the B<outlen> parameter. If B<out> is not B<NULL> then
before the call the B<outlen> parameter should contain the length of the
B<out> buffer, if the call is successful the encrypted data is written to
B<out> and the amount of data written to B<outlen>.

=head1 NOTES

After the call to EVP_PKEY_encrypt_init() algorithm specific control
operations can be performed to set any appropriate parameters for the
operation.  These operations can be included in the EVP_PKEY_encrypt_init_ex()
call.

The function EVP_PKEY_encrypt() can be called more than once on the same
context if several operations are performed using the same parameters.

=head1 RETURN VALUES

EVP_PKEY_encrypt_init(), EVP_PKEY_encrypt_init_ex() and EVP_PKEY_encrypt()
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 EXAMPLES

Encrypt data using OAEP (for RSA keys). See also L<PEM_read_PUBKEY(3)> or
L<d2i_X509(3)> for means to load a public key. You may also simply
set 'eng = NULL;' to start with the default OpenSSL RSA implementation:

 #include <openssl/evp.h>
 #include <openssl/rsa.h>
 #include <openssl/engine.h>

 EVP_PKEY_CTX *ctx;
 ENGINE *eng;
 unsigned char *out, *in;
 size_t outlen, inlen;
 EVP_PKEY *key;

 /*
  * NB: assumes eng, key, in, inlen are already set up,
  * and that key is an RSA public key
  */
 ctx = EVP_PKEY_CTX_new(key, eng);
 if (!ctx)
     /* Error occurred */
 if (EVP_PKEY_encrypt_init(ctx) <= 0)
     /* Error */
 if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_OAEP_PADDING) <= 0)
     /* Error */

 /* Determine buffer length */
 if (EVP_PKEY_encrypt(ctx, NULL, &outlen, in, inlen) <= 0)
     /* Error */

 out = OPENSSL_malloc(outlen);

 if (!out)
     /* malloc failure */

 if (EVP_PKEY_encrypt(ctx, out, &outlen, in, inlen) <= 0)
     /* Error */

 /* Encrypted data is outlen bytes written to buffer out */

=head1 SEE ALSO

L<d2i_X509(3)>,
L<ENGINE_by_id(3)>,
L<EVP_PKEY_CTX_new(3)>,
L<EVP_PKEY_decrypt(3)>,
L<EVP_PKEY_sign(3)>,
L<EVP_PKEY_verify(3)>,
L<EVP_PKEY_verify_recover(3)>,
L<EVP_PKEY_derive(3)>

=head1 HISTORY

These functions were added in OpenSSL 1.0.0.

=head1 COPYRIGHT

Copyright 2006-2021 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>.

=cut
