=pod

=head1 NAME

EVP_PKEY_encrypt_init, EVP_PKEY_encrypt - encrypt using a public key algorithm

=head1 SYNOPSIS

 #include <openssl/evp.h>

 int EVP_PKEY_sign_init(EVP_PKEY_CTX *ctx);
 int EVP_PKEY_sign(EVP_PKEY_CTX *ctx,
			unsigned char *sig, size_t *siglen,
			const unsigned char *tbs, size_t tbslen);

=head1 DESCRIPTION

The EVP_PKEY_sign_init() function initializes a public key algorithm
context using key B<pkey> for a signing operation.

The EVP_PKEY_sign() function performs a public key signing operation
using B<ctx>. The data to be signed is specified using the B<tbs> and
B<tbslen> parameters. If B<sig> is B<NULL> then the maximum size of the output
buffer is written to the B<siglen> parameter. If B<sig> is not B<NULL> then
before the call the B<siglen> parameter should contain the length of the
B<sig> buffer, if the call is successful the signature is written to
B<sig> and the amount of data written to B<siglen>.

=head1 NOTES

After the call to EVP_PKEY_sign_init() algorithm specific control
operations can be performed to set any appropriate parameters for the
operation.

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

=head1 RETURN VALUES

EVP_PKEY_sign_init() and EVP_PKEY_sign() 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 EXAMPLE

Sign data using PKCS#1 and SHA256 digest:

[to be added]

=head1 SEE ALSO

L<EVP_PKEY_CTX_new(3)|EVP_PKEY_CTX_new(3)>,
L<EVP_PKEY_encrypt(3)|EVP_PKEY_encrypt(3)>,
L<EVP_PKEY_decrypt(3)|EVP_PKEY_decrypt(3)>,
L<EVP_PKEY_verify(3)|EVP_PKEY_verify(3)>,
L<EVP_PKEY_verifyrecover(3)|EVP_PKEY_verifyrecover(3)>,
L<EVP_PKEY_derive(3)|EVP_PKEY_derive(3)> 

=head1 HISTORY

These functions were first added to OpenSSL 0.9.9.

=cut