NAME

       EVP_OpenInit, EVP_OpenUpdate, EVP_OpenFinal - EVP envelope decryption

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);
        int EVP_OpenUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
                           int *outl, unsigned char *in, int inl);
        int EVP_OpenFinal(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl);

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() initializes a cipher context ctx for decryption with cipher type. It
       decrypts the encrypted symmetric key of length ekl bytes passed in the ek parameter using
       the private key priv.  The IV is supplied in the iv parameter.

       EVP_OpenUpdate() and EVP_OpenFinal() have exactly the same properties as the
       EVP_DecryptUpdate() and EVP_DecryptFinal() routines, as documented on the
       EVP_EncryptInit(3) manual page.

NOTES

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

       If the cipher passed in the type parameter is a variable length cipher then the key length
       will be set to the value of the recovered key length. If the cipher is a fixed length
       cipher then the recovered key length must match the fixed cipher length.

RETURN VALUES

       EVP_OpenInit() returns 0 on error or a non zero integer (actually the recovered secret key
       size) if successful.

       EVP_OpenUpdate() returns 1 for success or 0 for failure.

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

SEE ALSO

       evp(7), RAND_bytes(3), EVP_EncryptInit(3), EVP_SealInit(3)

COPYRIGHT

       Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (the "License").  You may not use this file except
       in compliance with the License.  You can obtain a copy in the file LICENSE in the source
       distribution or at <https://www.openssl.org/source/license.html>.