Add some EVP_PKEY_METHOD docs.

=pod

=head1 NAME

EVP_PKEY_CTX_new, EVP_PKEY_CTX_new_id, EVP_PKEY_CTX_dup, EVP_PKEY_CTX_free - public key algorithm context functions.

=head1 SYNOPSIS

 #include <openssl/evp.h>

 EVP_PKEY_CTX *EVP_PKEY_CTX_new(EVP_PKEY *pkey, ENGINE *e);

 EVP_PKEY_CTX *EVP_PKEY_CTX_new_id(int id, ENGINE *e);

 EVP_PKEY_CTX *EVP_PKEY_CTX_dup(EVP_PKEY_CTX *ctx);

 void EVP_PKEY_CTX_free(EVP_PKEY_CTX *ctx);

=head1 DESCRIPTION

The EVP_PKEY_CTX_new() function allocates public key algorithm context using

the algorithm specified in B<pkey> and ENGINE B<e>.

The EVP_PKEY_CTX_new_id() function allocates public key algorithm context

using the algorithm specified by B<id> and ENGINE B<e>. It is normally used

when no B<EVP_PKEY> structure is associated with the operations, for example

during parameter generation of key genration for some algorithms.

EVP_PKEY_CTX_dup() duplicates the context B<ctx>.

EVP_PKEY_CTX_free() frees up the context B<ctx>.

=head1 NOTES

The B<EVP_PKEY_CTX> structure is an opaque public key algorithm context used

by the OpenSSL high level public key API. Contexts B<MUST NOT> be shared between

threads: that is it is not permissible to use the same context simultaneously

in two threads.

=head1 RETURN VALUES

EVP_PKEY_CTX_new(), EVP_PKEY_CTX_new_id(), EVP_PKEY_CTX_dup() returns either

the newly allocated B<EVP_PKEY_CTX> structure of B<NULL> if an error occurred.

EVP_PKEY_CTX_free() does not return a value.

=head1 SEE ALSO

L<EVP_PKEY_new(3)|EVP_PKEY_new(3)>

=head1 HISTORY

These functions were first added to OpenSSL 0.9.9.

=cut

=pod

=head1 NAME

EVP_PKEY_decrypt_init, EVP_PKEY_decrypt - decrypt using a public key algorithm

=head1 SYNOPSIS

 #include <openssl/evp.h>

 int EVP_PKEY_decrypt_init(EVP_PKEY_CTX *ctx);

 int EVP_PKEY_decrypt(EVP_PKEY_CTX *ctx,

			unsigned char *out, size_t *outlen,

			const unsigned char *in, size_t inlen);

=head1 DESCRIPTION

The EVP_PKEY_decrypt_init() function initializes a public key algorithm

context using key B<pkey> for a decryption operation.

The EVP_PKEY_decrypt() function performs a public key decryption operation

using B<ctx>. The data to be decrypted 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 decrypted data is written to

B<out> and the amount of data written to B<outlen>.

=head1 NOTES

After the call to EVP_PKEY_decrypt_init() algorithm specific control

operations can be performed to set any appropriate parameters for the

operation.

The function EVP_PKEY_decrypt() can be called more than once on the same

context if several operations are performed using the same parameters.

=head1 RETURN VALUES

EVP_PKEY_decrypt_init() and EVP_PKEY_decrypt() return 1 for success and 0

or a negative value for failure.

=head1 EXAMPLE

Decrypt data using OAEP (for RSA keys):

[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_sign(3)|EVP_PKEY_sign(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

=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_encrypt_init(EVP_PKEY_CTX *ctx);

 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() 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.

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() and EVP_PKEY_encrypt() return 1 for success and 0

or a negative value for failure.

=head1 EXAMPLE

Encrypt data using OAEP (for RSA keys):

[to be added]

=head1 SEE ALSO

L<EVP_PKEY_CTX_new(3)|EVP_PKEY_CTX_new(3)>,

L<EVP_PKEY_decrypt(3)|EVP_PKEY_decrypt(3)>,

L<EVP_PKEY_sign(3)|EVP_PKEY_sign(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

Symmetric encryption is available with the B<EVP_Encrypt>I<...>

functions.  The B<EVP_Digest>I<...> functions provide message digests.

The B<EVP_PKEY>I<...> functions provide a high level interface to

asymmetric algorithms.

Algorithms are loaded with OpenSSL_add_all_algorithms(3).

All the symmetric algorithms (ciphers) and digests can be replaced by ENGINE

modules providing alternative implementations. If ENGINE implementations of

ciphers or digests are registered as defaults, then the various EVP functions

will automatically use those implementations automatically in preference to

built in software implementations. For more information, consult the engine(3)

man page.

All the symmetric algorithms (ciphers), digests and asymmetric algorithms

(public key algorithms) can be replaced by ENGINE modules providing alternative

implementations. If ENGINE implementations of ciphers or digests are registered

as defaults, then the various EVP functions will automatically use those

implementations automatically in preference to built in software

implementations. For more information, consult the engine(3) man page.

Although low level algorithm specific functions exist for many algorithms

their use is discouraged. They cannot be used with an ENGINE and ENGINE

versions of new algorithms cannot be accessed using the low level functions.

Also makes code harder to adapt to new algorithms and some options are not 

cleanly supported at the low level and some operations are more efficient

using the high level interface.

=head1 SEE ALSO