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Title "EVP 7" For nroff, turn off justification. Always turn off hyphenation; it makes
way too many mistakes in technical documents.
evp - high-level cryptographic functions Header "SYNOPSIS" .Vb 1 #include <openssl/evp.h> .Ve Header "DESCRIPTION" The \s-1EVP\s0 library provides a high-level interface to cryptographic functions.

The EVP_Seal\s-1XXX\s0 and EVP_Open\s-1XXX\s0 functions provide public key encryption and decryption to implement digital \*(L"envelopes\*(R".

The EVP_DigestSign\s-1XXX\s0 and \fBEVP_DigestVerify\s-1XXX\s0 functions implement digital signatures and Message Authentication Codes (MACs). Also see the older \fBEVP_Sign\s-1XXX\s0 and EVP_Verify\s-1XXX\s0 functions.

Symmetric encryption is available with the EVP_Encrypt\s-1XXX\s0 functions. The EVP_Digest\s-1XXX\s0 functions provide message digests.

The \s-1EVP_PKEY\s0\s-1XXX\s0 functions provide a high-level interface to asymmetric algorithms. To create a new \s-1EVP_PKEY\s0 see \fBEVP_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 \fBEVP_PKEY_print_private\|(3). EVP_PKEY_todata\|(3) can be used to convert a key back into an \s-1OSSL_PARAM\s0\|(3) array.

The \s-1EVP_PKEY\s0 functions support the full range of asymmetric algorithm operations:

Item "For key agreement see EVP_PKEY_derive"

0

Item "For signing and verifying see EVP_PKEY_sign, EVP_PKEY_verify and EVP_PKEY_verify_recover. However, note that these functions do not perform a digest of the data to be signed. Therefore, normally you would use the EVP_DigestSignInit functions for this purpose." Item "For encryption and decryption see EVP_PKEY_encrypt and EVP_PKEY_decrypt 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 and EVP_OpenInit functions."

The EVP_BytesToKey\|(3) function provides some limited support for password based encryption. Careful selection of the parameters will provide a PKCS#5 \s-1PBKDF1\s0 compatible implementation. However, new applications should not typically use this (preferring, for example, \s-1PBKDF2\s0 from PCKS#5).

The EVP_Encode\s-1XXX\s0 and \fBEVP_Decode\s-1XXX\s0 functions implement base 64 encoding and decoding.

All the symmetric algorithms (ciphers), digests and asymmetric algorithms (public key algorithms) can be replaced by \s-1ENGINE\s0 modules providing alternative implementations. If \s-1ENGINE\s0 implementations of ciphers or digests are registered as defaults, then the various \s-1EVP\s0 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 \s-1ENGINE\s0 and \s-1ENGINE\s0 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.

Header "SEE ALSO" \fBEVP_DigestInit\|(3), \fBEVP_EncryptInit\|(3), \fBEVP_OpenInit\|(3), \fBEVP_SealInit\|(3), \fBEVP_DigestSignInit\|(3), \fBEVP_SignInit\|(3), \fBEVP_VerifyInit\|(3), \fBEVP_EncodeInit\|(3), \fBEVP_PKEY_new\|(3), \fBEVP_PKEY_fromdata\|(3), \fBEVP_PKEY_todata\|(3), \fBEVP_PKEY_keygen\|(3), \fBEVP_PKEY_print_private\|(3), \fBEVP_PKEY_decrypt\|(3), \fBEVP_PKEY_encrypt\|(3), \fBEVP_PKEY_sign\|(3), \fBEVP_PKEY_verify\|(3), \fBEVP_PKEY_verify_recover\|(3), \fBEVP_PKEY_derive\|(3), \fBEVP_BytesToKey\|(3), \fBENGINE_by_id\|(3) Header "COPYRIGHT" Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.