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.\" ========================================================================
.\"
.IX Title "EVP 7"
.TH EVP 7 "2023-09-11" "1.1.1w" "OpenSSL"
.\" For nroff, turn off justification. Always turn off hyphenation; it makes
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.nh
.SH "NAME"
evp \- high\-level cryptographic functions
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/evp.h>
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \s-1EVP\s0 library provides a high-level interface to cryptographic
functions.
.PP
The \fBEVP_Seal\fR\fI\s-1XXX\s0\fR and \fBEVP_Open\fR\fI\s-1XXX\s0\fR
functions provide public key encryption and decryption to implement digital \*(L"envelopes\*(R".
.PP
The \fBEVP_DigestSign\fR\fI\s-1XXX\s0\fR and
\&\fBEVP_DigestVerify\fR\fI\s-1XXX\s0\fR functions implement
digital signatures and Message Authentication Codes (MACs). Also see the older
\&\fBEVP_Sign\fR\fI\s-1XXX\s0\fR and \fBEVP_Verify\fR\fI\s-1XXX\s0\fR
functions.
.PP
Symmetric encryption is available with the \fBEVP_Encrypt\fR\fI\s-1XXX\s0\fR
functions. The \fBEVP_Digest\fR\fI\s-1XXX\s0\fR functions provide message digests.
.PP
The \fB\s-1EVP_PKEY\s0\fR\fI\s-1XXX\s0\fR functions provide a high-level interface to
asymmetric algorithms. To create a new \s-1EVP_PKEY\s0 see
\&\fBEVP_PKEY_new\fR\|(3). EVP_PKEYs can be associated
with a private key of a particular algorithm by using the functions
described on the \fBEVP_PKEY_set1_RSA\fR\|(3) page, or
new keys can be generated using \fBEVP_PKEY_keygen\fR\|(3).
EVP_PKEYs can be compared using \fBEVP_PKEY_cmp\fR\|(3), or printed using
\&\fBEVP_PKEY_print_private\fR\|(3).
.PP
The \s-1EVP_PKEY\s0 functions support the full range of asymmetric algorithm operations:
.IP "For key agreement see \fBEVP_PKEY_derive\fR\|(3)" 4
.IX Item "For key agreement see EVP_PKEY_derive"
.PD 0
.IP "For signing and verifying see \fBEVP_PKEY_sign\fR\|(3), \fBEVP_PKEY_verify\fR\|(3) and \fBEVP_PKEY_verify_recover\fR\|(3). However, note that these functions do not perform a digest of the data to be signed. Therefore, normally you would use the \fBEVP_DigestSignInit\fR\|(3) functions for this purpose." 4
.IX 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."
.ie n .IP "For encryption and decryption see \fBEVP_PKEY_encrypt\fR\|(3) and \fBEVP_PKEY_decrypt\fR\|(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 \fBEVP_SealInit\fR\|(3) and \fBEVP_OpenInit\fR\|(3) functions." 4
.el .IP "For encryption and decryption see \fBEVP_PKEY_encrypt\fR\|(3) and \fBEVP_PKEY_decrypt\fR\|(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 \fBEVP_SealInit\fR\|(3) and \fBEVP_OpenInit\fR\|(3) functions." 4
.IX 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."
.PD
.PP
The \fBEVP_BytesToKey\fR\|(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).
.PP
The \fBEVP_Encode\fR\fI\s-1XXX\s0\fR and
\&\fBEVP_Decode\fR\fI\s-1XXX\s0\fR functions implement base 64 encoding
and decoding.
.PP
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 \fBengine\fR\|(3) man page.
.PP
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.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBEVP_DigestInit\fR\|(3),
\&\fBEVP_EncryptInit\fR\|(3),
\&\fBEVP_OpenInit\fR\|(3),
\&\fBEVP_SealInit\fR\|(3),
\&\fBEVP_DigestSignInit\fR\|(3),
\&\fBEVP_SignInit\fR\|(3),
\&\fBEVP_VerifyInit\fR\|(3),
\&\fBEVP_EncodeInit\fR\|(3),
\&\fBEVP_PKEY_new\fR\|(3),
\&\fBEVP_PKEY_set1_RSA\fR\|(3),
\&\fBEVP_PKEY_keygen\fR\|(3),
\&\fBEVP_PKEY_print_private\fR\|(3),
\&\fBEVP_PKEY_decrypt\fR\|(3),
\&\fBEVP_PKEY_encrypt\fR\|(3),
\&\fBEVP_PKEY_sign\fR\|(3),
\&\fBEVP_PKEY_verify\fR\|(3),
\&\fBEVP_PKEY_verify_recover\fR\|(3),
\&\fBEVP_PKEY_derive\fR\|(3),
\&\fBEVP_BytesToKey\fR\|(3),
\&\fBENGINE_by_id\fR\|(3)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2000\-2020 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the OpenSSL license (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>.
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