OpenSSL.vip

Cryptography and SSL/TLS Toolkit

NAME

EVP_SealInit, EVP_SealUpdate, EVP_SealFinal - EVP envelope encryption

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);

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_aes_256_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 public keys.

The 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 iv parameter 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 RETURN VALUES

EVP_SealInit() returns 0 on error or npubk if successful.

EVP_SealUpdate() and EVP_SealFinal() return 1 for success and 0 for failure.

NOTES

Because a random secret key is generated the random number generator must be seeded when EVP_SealInit() is called. If the automatic seeding or reseeding of the OpenSSL CSPRNG fails due to external circumstances (see SEE ALSO

RAND_bytes(3), EVP_OpenInit(3), COPYRIGHT

Copyright 2000-2016 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.

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