- NAME
- SYNOPSIS
- DESCRIPTION
- SEE ALSO
- COPYRIGHT

# 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_Seal XXX and EVP_Open XXX functions provide public key encryption and decryption to implement digital "envelopes".

The EVP_DigestSign XXX and EVP_DigestVerify XXX functions implement digital signatures and Message Authentication Codes (MACs). Also see the older EVP_Sign XXX and EVP_Verify XXX functions.

Symmetric encryption is available with the EVP_Encrypt XXX functions. The EVP_Digest XXX functions provide message digests.

The EVP_PKEY XXX 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_Encode XXX and EVP_Decode XXX functions implement base64 encoding and decoding.

Providers can supply implementations for a wide range of cryptographic operations, including symmetric algorithms (ciphers), digests, asymmetric algorithms (public key algorithms), key management, parameter generation, and more. For more information, consult the provider(7) man page.

Although low-level algorithm specific functions exist for many algorithms, their use is discouraged. They do not call into providers such as the fips provider and thus they are not FIPS 140-3 validated. If an accelerated implementation of an algorithm is provided through a third party provider the low level API will not use that implementation either.

# 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),

# COPYRIGHT

Copyright 2000-2025 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.