| =pod |
| |
| =head1 NAME |
| |
| evp - high-level cryptographic functions |
| |
| =head1 SYNOPSIS |
| |
| #include <openssl/evp.h> |
| |
| =head1 DESCRIPTION |
| |
| The EVP library provides a high-level interface to cryptographic |
| functions. |
| |
| The L<B<EVP_Seal>I<XXX>|EVP_SealInit(3)> and L<B<EVP_Open>I<XXX>|EVP_OpenInit(3)> |
| functions provide public key encryption and decryption to implement digital "envelopes". |
| |
| The L<B<EVP_DigestSign>I<XXX>|EVP_DigestSignInit(3)> and |
| L<B<EVP_DigestVerify>I<XXX>|EVP_DigestVerifyInit(3)> functions implement |
| digital signatures and Message Authentication Codes (MACs). Also see the older |
| L<B<EVP_Sign>I<XXX>|EVP_SignInit(3)> and L<B<EVP_Verify>I<XXX>|EVP_VerifyInit(3)> |
| functions. |
| |
| Symmetric encryption is available with the L<B<EVP_Encrypt>I<XXX>|EVP_EncryptInit(3)> |
| functions. The L<B<EVP_Digest>I<XXX>|EVP_DigestInit(3)> functions provide message digests. |
| |
| The B<EVP_PKEY>I<XXX> functions provide a high-level interface to |
| asymmetric algorithms. To create a new EVP_PKEY see |
| L<EVP_PKEY_new(3)>. EVP_PKEYs can be associated |
| with a private key of a particular algorithm by using the functions |
| described on the L<EVP_PKEY_set1_RSA(3)> page, or |
| new keys can be generated using L<EVP_PKEY_keygen(3)>. |
| EVP_PKEYs can be compared using L<EVP_PKEY_cmp(3)>, or printed using |
| L<EVP_PKEY_print_private(3)>. |
| |
| The EVP_PKEY functions support the full range of asymmetric algorithm operations: |
| |
| =over 4 |
| |
| =item For key agreement see L<EVP_PKEY_derive(3)> |
| |
| =item For signing and verifying see L<EVP_PKEY_sign(3)>, |
| L<EVP_PKEY_verify(3)> and L<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 L<EVP_DigestSignInit(3)> |
| functions for this purpose. |
| |
| =item For encryption and decryption see L<EVP_PKEY_encrypt(3)> |
| and L<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 L<EVP_SealInit(3)> and |
| L<EVP_OpenInit(3)> functions. |
| |
| =back |
| |
| The L<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 L<B<EVP_Encode>I<XXX>|EVP_EncodeInit(3)> and |
| L<B<EVP_Decode>I<XXX>|EVP_EncodeInit(3)> 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. |
| |
| =head1 SEE ALSO |
| |
| L<EVP_DigestInit(3)>, |
| L<EVP_EncryptInit(3)>, |
| L<EVP_OpenInit(3)>, |
| L<EVP_SealInit(3)>, |
| L<EVP_DigestSignInit(3)>, |
| L<EVP_SignInit(3)>, |
| L<EVP_VerifyInit(3)>, |
| L<EVP_EncodeInit(3)>, |
| L<EVP_PKEY_new(3)>, |
| L<EVP_PKEY_set1_RSA(3)>, |
| L<EVP_PKEY_keygen(3)>, |
| L<EVP_PKEY_print_private(3)>, |
| L<EVP_PKEY_decrypt(3)>, |
| L<EVP_PKEY_encrypt(3)>, |
| L<EVP_PKEY_sign(3)>, |
| L<EVP_PKEY_verify(3)>, |
| L<EVP_PKEY_verify_recover(3)>, |
| L<EVP_PKEY_derive(3)>, |
| L<EVP_BytesToKey(3)>, |
| L<ENGINE_by_id(3)> |
| |
| =head1 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 |
| L<https://www.openssl.org/source/license.html>. |
| |
| =cut |