EVP_SealInit(3)             OpenSSL             EVP_SealInit(3)





NAME
       EVP_SealInit, EVP_SealUpdate, EVP_SealFinal - EVP enve-
       lope encryption

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);
        int EVP_SealUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
                int *outl, unsigned char *in, int inl);
        int EVP_SealFinal(EVP_CIPHER_CTX *ctx, unsigned char *out,
                int *outl);

DESCRIPTION
       The EVP envelope routines are a high level interface to
       envelope encryption. They generate a random key and IV
       (if required) then "envelope" it by using public key
       encryption. Data can then be encrypted using this key.

       EVP_SealInit() initializes a cipher context ctx for
       encryption with cipher type using a random secret key
       and IV. 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. 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 ek[i] must have room for EVP_PKEY_size(pubk[i])
       bytes. The actual size of each encrypted secret key is
       written to the array ekl. pubk is an array of npubk pub-
       lic keys.

       The iv parameter is a buffer where the generated IV is
       written to. It must contain enough room for the corre-
       sponding cipher's IV, as determined by (for example)
       EVP_CIPHER_iv_length(type).

       If the cipher does not require an IV then the iv parame-
       ter is ignored and can be NULL.

       EVP_SealUpdate() and EVP_SealFinal() have exactly the
       same properties as the EVP_EncryptUpdate() and
       EVP_EncryptFinal() routines, as documented on the
       EVP_EncryptInit(3) manual page.

RETURN VALUES
       EVP_SealInit() returns 0 on error or npubk if success-
       ful.

       EVP_SealUpdate() and EVP_SealFinal() return 1 for suc-
       cess and 0 for failure.

NOTES
       Because a random secret key is generated the random num-
       ber 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 trans-
       port.

       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.

       It is possible to call EVP_SealInit() twice in the same
       way as EVP_EncryptInit(). The first call should have
       npubk set to 0 and (after setting any cipher parameters)
       it should be called again with type set to NULL.

SEE ALSO
       evp(3), rand(3), EVP_EncryptInit(3), EVP_OpenInit(3)

HISTORY
       EVP_SealFinal() did not return a value before OpenSSL
       0.9.7.



0.9.7c                     2003-01-26           EVP_SealInit(3)
