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download PDF document: evp.7ossl.pdf

EVP(7ossl) OpenSSL EVP(7ossl)

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_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 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_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 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>.
3.0.11 2023-09-19 EVP(7ossl)