Manual pages for EVP_Open* and EVP_Seal*

=pod

=head1 NAME

EVP_OpenInit, EVP_OpenUpdate, EVP_OpenFinal - EVP envelope decryption

=head1 SYNOPSIS

 #include <openssl/evp.h>

 int EVP_OpenInit(EVP_CIPHER_CTX *ctx,EVP_CIPHER *type,unsigned char *ek,

		int ekl,unsigned char *iv,EVP_PKEY *priv);

 void EVP_OpenUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,

         int *outl, unsigned char *in, int inl);

 void EVP_OpenFinal(EVP_CIPHER_CTX *ctx, unsigned char *out,

         int *outl);

=head1 DESCRIPTION

The EVP envelope routines are a high level interface to envelope

decryption. They decrypt a public key encrypted symmetric key and

then decrypt data using it.

EVP_OpenInit() initialises a cipher context B<ctx> for decryption

with cipher B<type>. It decrypts the encrypted symmetric key of length

B<ekl> bytes passed in the B<ek> parameter using the private key B<priv>.

The IV is supplied in the B<iv> parameter.

EVP_OpenUpdate() and EVP_OpenFinal() have exactly the same properties

as the EVP_DecryptUpdate() and EVP_DecryptFinal() routines, as 

documented on the L<EVP_EncryptInit(3)|EVP_EncryptInit(3)> manual

page. 

=head1 RETURN VALUES

EVP_OpenInit() returns -1 on error or an non zero integer (actually the

recovered secret key size) if successful.

EVP_SealUpdate() does not return a value.

EVP_SealFinal() returns 0 if the decrypt failed or 1 for success.

=head1 SEE ALSO

L<evp(3)|evp(3)>,L<rand(3)|rand(3)>

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

L<EVP_SealInit(3)|EVP_SealInit(3)>

=head1 HISTORY

=cut

=pod

=head1 NAME

EVP_SealInit, EVP_SealUpdate, EVP_SealFinal - EVP envelope encryption

=head1 SYNOPSIS

 #include <openssl/evp.h>

 int EVP_SealInit(EVP_CIPHER_CTX *ctx, EVP_CIPHER *type, unsigned char **ek,

		int *ekl, unsigned char *iv,EVP_PKEY **pubk, int npubk);

 void EVP_SealUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,

         int *outl, unsigned char *in, int inl);

 void EVP_SealFinal(EVP_CIPHER_CTX *ctx, unsigned char *out,

         int *outl);

=head1 DESCRIPTION

The EVP envelope routines are a high level interface to envelope

encryption. They generate a random key and then "envelope" it by

using public key encryption. Data can then be encrypted using this

key.

EVP_SealInit() initialises a cipher context B<ctx> for encryption

with cipher B<type> using a random secret key and IV supplied in

the B<iv> parameter. B<type> is normally supplied by a function such

as EVP_des_cbc(). The secret key is encrypted using one or more public

keys, this allows the same encrypted data to be decrypted using any

of the corresponding private keys. B<ek> is an array of buffers where

the public key encrypted secret key will be written, each buffer must

contain enough room for the corresponding encrypted key: that is

B<ek[i]> must have room for B<EVP_PKEY_size(pubk[i])> bytes. The actual

size of each encrypted secret key is written to the array B<ekl>. B<pubk> is

an array of B<npubk> public keys.

EVP_SealUpdate() and EVP_SealFinal() have exactly the same properties

as the EVP_EncryptUpdate() and EVP_EncryptFinal() routines, as 

documented on the L<EVP_EncryptInit(3)|EVP_EncryptInit(3)> manual

page. 

=head1 RETURN VALUES

EVP_SealInit() returns -1 on error or B<npubk> if successful.

EVP_SealUpdate() and EVP_SealFinal() do not return values.

=head1 NOTES

Because a random secret key is generated the random number generator

must be seeded before calling EVP_SealInit().

The public key must be RSA because it is the only OpenSSL public key

algorithm that supports key transport.

Envelope encryption is the usual method of using public key encryption

on large amounts of data, this is because public key encryption is slow

but symmetric encryption is fast. So symmetric encryption is used for

bulk encryption and the small random symmetric key used is transferred

using public key encryption.

=head1 SEE ALSO

L<evp(3)|evp(3)>,L<rand(3)|rand(3)>

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

L<EVP_OpenInit(3)|EVP_OpenInit(3)>

=head1 HISTORY

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