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Diffstat (limited to 'openssl/doc/crypto/EVP_SealInit.pod')
-rw-r--r-- | openssl/doc/crypto/EVP_SealInit.pod | 85 |
1 files changed, 85 insertions, 0 deletions
diff --git a/openssl/doc/crypto/EVP_SealInit.pod b/openssl/doc/crypto/EVP_SealInit.pod new file mode 100644 index 000000000..7d793e19e --- /dev/null +++ b/openssl/doc/crypto/EVP_SealInit.pod @@ -0,0 +1,85 @@ +=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, 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, + int *outl); + +=head1 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 B<ctx> for encryption +with cipher B<type> using a random secret key and IV. 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. + +The B<iv> 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 B<iv> parameter is ignored +and can be B<NULL>. + +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 0 on error or B<npubk> if successful. + +EVP_SealUpdate() and EVP_SealFinal() return 1 for success and 0 for +failure. + +=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. + +It is possible to call EVP_SealInit() twice in the same way as +EVP_EncryptInit(). The first call should have B<npubk> set to 0 +and (after setting any cipher parameters) it should be called again +with B<type> set to NULL. + +=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 + +EVP_SealFinal() did not return a value before OpenSSL 0.9.7. + +=cut |