.\"	$OpenBSD: EVP_PKEY_encrypt.3,v 1.7 2022/03/31 17:27:17 naddy Exp $
.\"	OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100
.\"
.\" This file was written by Dr. Stephen Henson <steve@openssl.org>.
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.Dd $Mdocdate: March 31 2022 $
.Dt EVP_PKEY_ENCRYPT 3
.Os
.Sh NAME
.Nm EVP_PKEY_encrypt_init ,
.Nm EVP_PKEY_encrypt
.Nd encrypt using a public key algorithm
.Sh SYNOPSIS
.In openssl/evp.h
.Ft int
.Fo EVP_PKEY_encrypt_init
.Fa "EVP_PKEY_CTX *ctx"
.Fc
.Ft int
.Fo EVP_PKEY_encrypt
.Fa "EVP_PKEY_CTX *ctx"
.Fa "unsigned char *out"
.Fa "size_t *outlen"
.Fa "const unsigned char *in"
.Fa "size_t inlen"
.Fc
.Sh DESCRIPTION
The
.Fn EVP_PKEY_encrypt_init
function initializes a public key algorithm context using key
.Fa ctx->pkey
for an encryption operation.
.Pp
The
.Fn EVP_PKEY_encrypt
function performs a public key encryption operation using
.Fa ctx .
The data to be encrypted is specified using the
.Fa in
and
.Fa inlen
parameters.
If
.Fa out
is
.Dv NULL ,
then the maximum size of the output buffer is written to the
.Fa outlen
parameter.
If
.Fa out
is not
.Dv NULL ,
then before the call the
.Fa outlen
parameter should contain the length of the
.Fa out
buffer.
If the call is successful, the encrypted data is written to
.Fa out
and the amount of data written to
.Fa outlen .
.Pp
After the call to
.Fn EVP_PKEY_encrypt_init ,
algorithm specific control operations can be performed to set any
appropriate parameters for the operation.
.Pp
The function
.Fn EVP_PKEY_encrypt
can be called more than once on the same context if several operations
are performed using the same parameters.
.Sh RETURN VALUES
.Fn EVP_PKEY_encrypt_init
and
.Fn 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.
.Sh EXAMPLES
Encrypt data using OAEP (for RSA keys).
See also
.Xr PEM_read_PUBKEY 3
and
.Xr d2i_X509 3
for means to load a public key.
You may also simply set
.Ql eng = NULL;
to start with the default OpenSSL RSA implementation:
.Bd -literal -offset indent
#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_PKCS1_OAEP_PADDING) <= 0)
	/* Error */

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

out = 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 */
.Ed
.Sh SEE ALSO
.Xr EVP_PKEY_CTX_new 3 ,
.Xr EVP_PKEY_decrypt 3 ,
.Xr EVP_PKEY_derive 3 ,
.Xr EVP_PKEY_meth_set_encrypt 3 ,
.Xr EVP_PKEY_sign 3 ,
.Xr EVP_PKEY_verify 3 ,
.Xr EVP_PKEY_verify_recover 3
.Sh HISTORY
.Fn EVP_PKEY_encrypt_init
and
.Fn EVP_PKEY_encrypt
first appeared in OpenSSL 1.0.0 and have been available since
.Ox 4.9 .