evp - high-level cryptographic functions
The EVP library provides a high-level interface to cryptographic functions.
public key encryption and decryption to implement digital
functions implement digital signatures and Message Authentication Codes
(MACs). Also see the older EVP_SignXXX
Symmetric encryption is available with the EVP_EncryptXXX
functions. The EVP_DigestXXX
functions provide message digests.
functions provide a high level interface to
asymmetric algorithms. To create a new EVP_PKEY see EVP_PKEY_new
EVP_PKEYs can be associated with a private key of a particular algorithm by
using the functions described on the EVP_PKEY_set1_RSA
(3) page, or new
keys can be generated using EVP_PKEY_keygen
(3). EVP_PKEYs can be
compared using EVP_PKEY_cmp
(3), or printed using
The EVP_PKEY functions support the full range of asymmetric algorithm
- For key agreement see EVP_PKEY_derive(3)
- For signing and verifying see EVP_PKEY_sign(3),
EVP_PKEY_verify(3) and EVP_PKEY_verify_recover(3). However,
note that these functions do not perform a digest of the data to be signed.
Therefore normally you would use the EVP_DigestSignInit(3) functions
for this purpose.
- For encryption and decryption see EVP_PKEY_encrypt(3) and
EVP_PKEY_decrypt(3) respectively. However, note that these functions
perform encryption and decryption only. As public key encryption is an
expensive operation, normally you would wrap an encrypted message in a
"digital envelope" using the EVP_SealInit(3) and
(3) function provides some limited support for password
based encryption. Careful selection of the parameters will provide a PKCS#5
PBKDF1 compatible implementation. However, new applications should not
typically use this (preferring, for example, PBKDF2 from PCKS#5).
implement base 64 encoding and decoding.
All the symmetric algorithms (ciphers), digests and asymmetric algorithms
(public key algorithms) can be replaced by ENGINE modules providing
alternative implementations. If ENGINE implementations of ciphers or digests
are registered as defaults, then the various EVP functions will automatically
use those implementations automatically in preference to built in software
implementations. For more information, consult the engine
(3) man page.
Although low level algorithm specific functions exist for many algorithms their
use is discouraged. They cannot be used with an ENGINE and ENGINE versions of
new algorithms cannot be accessed using the low level functions. Also makes
code harder to adapt to new algorithms and some options are not cleanly
supported at the low level and some operations are more efficient using the
high level interface.
Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (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