EVP_SealInit, EVP_SealUpdate, EVP_SealFinal - EVP envelope encryption
int EVP_SealInit(EVP_CIPHER_CTX *ctx, const 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,
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.
initializes a cipher context ctx
with cipher type
using a random secret key and IV. type
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
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
must have room for EVP_PKEY_size(pubk[i])
actual size of each encrypted secret key is written to the array ekl
is an array of npubk
parameter is a buffer where the generated IV is written to. It
must contain enough room for the corresponding cipher's IV, as determined by
(for example) EVP_CIPHER_iv_length(type).
If the cipher does not require an IV then the iv
parameter is ignored and
can be NULL
have exactly the same
properties as the EVP_EncryptUpdate()
routines, as documented on the EVP_EncryptInit(3)
returns 0 on error or npubk
return 1 for success and 0
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
It is possible to call EVP_SealInit()
twice in the same way as
. The first call should have npubk
set to 0 and
(after setting any cipher parameters) it should be called again with
set to NULL.
did not return a value before OpenSSL 0.9.7.