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EVP(7)                              OpenSSL                             EVP(7)
NAME
       evp - high-level cryptographic functions
SYNOPSIS
        #include <openssl/evp.h>
DESCRIPTION
       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_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 EVP_PKEY_print_private(3).
       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.
SEE ALSO
       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_set1_RSA(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
       Copyright 2000-2020 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
       <https://www.openssl.org/source/license.html>;.
1.1.1k                            2021-03-25                            EVP(7)