evp - high-level cryptographic functions
#include <openssl/evp.h>
The EVP library provides a high-level interface to cryptographic functions.
The
EVP_SealXXX and
EVP_OpenXXX functions provide
public key encryption and decryption to implement digital
"envelopes".
The
EVP_DigestSignXXX and
EVP_DigestVerifyXXX
functions implement digital signatures and Message Authentication Codes
(MACs). Also see the older
EVP_SignXXX and
EVP_VerifyXXX functions.
Symmetric encryption is available with the
EVP_EncryptXXX
functions. The
EVP_DigestXXX functions provide message digests.
The
EVP_PKEYXXX functions provide a high-level interface to
asymmetric algorithms. To create a new EVP_PKEY see
EVP_PKEY_new(3).
EVP_PKEYs can be associated with a private key of a particular algorithm by
using the functions described on the
EVP_PKEY_fromdata(3) page, or new
keys can be generated using
EVP_PKEY_keygen(3). EVP_PKEYs can be
compared using
EVP_PKEY_eq(3), or printed using
EVP_PKEY_print_private(3).
EVP_PKEY_todata(3) can be used to
convert a key back into an
OSSL_PARAM(3) array.
The EVP_PKEY functions support the full range of asymmetric algorithm
operations:
- 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 EVP_OpenInit(3) functions.
The
EVP_BytesToKey(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).
The
EVP_EncodeXXX and
EVP_DecodeXXX functions
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.
EVP_DigestInit(3),
EVP_EncryptInit(3),
EVP_OpenInit(3),
EVP_SealInit(3),
EVP_DigestSignInit(3),
EVP_SignInit(3),
EVP_VerifyInit(3),
EVP_EncodeInit(3),
EVP_PKEY_new(3),
EVP_PKEY_fromdata(3),
EVP_PKEY_todata(3),
EVP_PKEY_keygen(3),
EVP_PKEY_print_private(3),
EVP_PKEY_decrypt(3),
EVP_PKEY_encrypt(3),
EVP_PKEY_sign(3),
EVP_PKEY_verify(3),
EVP_PKEY_verify_recover(3),
EVP_PKEY_derive(3),
EVP_BytesToKey(3),
ENGINE_by_id(3)
Copyright 2000-2021 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>.