1=pod 2 3=head1 NAME 4 5evp - high-level cryptographic functions 6 7=head1 SYNOPSIS 8 9 #include <openssl/evp.h> 10 11=head1 DESCRIPTION 12 13The EVP library provides a high-level interface to cryptographic 14functions. 15 16The L<B<EVP_Seal>I<XXX>|EVP_SealInit(3)> and L<B<EVP_Open>I<XXX>|EVP_OpenInit(3)> 17functions provide public key encryption and decryption to implement digital "envelopes". 18 19The L<B<EVP_DigestSign>I<XXX>|EVP_DigestSignInit(3)> and 20L<B<EVP_DigestVerify>I<XXX>|EVP_DigestVerifyInit(3)> functions implement 21digital signatures and Message Authentication Codes (MACs). Also see the older 22L<B<EVP_Sign>I<XXX>|EVP_SignInit(3)> and L<B<EVP_Verify>I<XXX>|EVP_VerifyInit(3)> 23functions. 24 25Symmetric encryption is available with the L<B<EVP_Encrypt>I<XXX>|EVP_EncryptInit(3)> 26functions. The L<B<EVP_Digest>I<XXX>|EVP_DigestInit(3)> functions provide message digests. 27 28The B<EVP_PKEY>I<XXX> functions provide a high-level interface to 29asymmetric algorithms. To create a new EVP_PKEY see 30L<EVP_PKEY_new(3)>. EVP_PKEYs can be associated 31with a private key of a particular algorithm by using the functions 32described on the L<EVP_PKEY_fromdata(3)> page, or 33new keys can be generated using L<EVP_PKEY_keygen(3)>. 34EVP_PKEYs can be compared using L<EVP_PKEY_eq(3)>, or printed using 35L<EVP_PKEY_print_private(3)>. L<EVP_PKEY_todata(3)> can be used to convert a 36key back into an L<OSSL_PARAM(3)> array. 37 38The EVP_PKEY functions support the full range of asymmetric algorithm operations: 39 40=over 4 41 42=item For key agreement see L<EVP_PKEY_derive(3)> 43 44=item For signing and verifying see L<EVP_PKEY_sign(3)>, 45L<EVP_PKEY_verify(3)> and L<EVP_PKEY_verify_recover(3)>. 46However, note that 47these functions do not perform a digest of the data to be signed. Therefore, 48normally you would use the L<EVP_DigestSignInit(3)> 49functions for this purpose. 50 51=item For encryption and decryption see L<EVP_PKEY_encrypt(3)> 52and L<EVP_PKEY_decrypt(3)> respectively. However, note that 53these functions perform encryption and decryption only. As public key 54encryption is an expensive operation, normally you would wrap 55an encrypted message in a "digital envelope" using the L<EVP_SealInit(3)> and 56L<EVP_OpenInit(3)> functions. 57 58=back 59 60The L<EVP_BytesToKey(3)> function provides some limited support for password 61based encryption. Careful selection of the parameters will provide a PKCS#5 PBKDF1 compatible 62implementation. However, new applications should not typically use this (preferring, for example, 63PBKDF2 from PCKS#5). 64 65The L<B<EVP_Encode>I<XXX>|EVP_EncodeInit(3)> and 66L<B<EVP_Decode>I<XXX>|EVP_EncodeInit(3)> functions implement base64 encoding 67and decoding. 68 69All the symmetric algorithms (ciphers), digests and asymmetric algorithms 70(public key algorithms) can be replaced by ENGINE modules providing alternative 71implementations. If ENGINE implementations of ciphers or digests are registered 72as defaults, then the various EVP functions will automatically use those 73implementations automatically in preference to built in software 74implementations. For more information, consult the engine(3) man page. 75 76Although low-level algorithm specific functions exist for many algorithms 77their use is discouraged. They cannot be used with an ENGINE and ENGINE 78versions of new algorithms cannot be accessed using the low-level functions. 79Also makes code harder to adapt to new algorithms and some options are not 80cleanly supported at the low-level and some operations are more efficient 81using the high-level interface. 82 83=head1 SEE ALSO 84 85L<EVP_DigestInit(3)>, 86L<EVP_EncryptInit(3)>, 87L<EVP_OpenInit(3)>, 88L<EVP_SealInit(3)>, 89L<EVP_DigestSignInit(3)>, 90L<EVP_SignInit(3)>, 91L<EVP_VerifyInit(3)>, 92L<EVP_EncodeInit(3)>, 93L<EVP_PKEY_new(3)>, 94L<EVP_PKEY_fromdata(3)>, 95L<EVP_PKEY_todata(3)>, 96L<EVP_PKEY_keygen(3)>, 97L<EVP_PKEY_print_private(3)>, 98L<EVP_PKEY_decrypt(3)>, 99L<EVP_PKEY_encrypt(3)>, 100L<EVP_PKEY_sign(3)>, 101L<EVP_PKEY_verify(3)>, 102L<EVP_PKEY_verify_recover(3)>, 103L<EVP_PKEY_derive(3)>, 104L<EVP_BytesToKey(3)>, 105L<ENGINE_by_id(3)> 106 107=head1 COPYRIGHT 108 109Copyright 2000-2024 The OpenSSL Project Authors. All Rights Reserved. 110 111Licensed under the Apache License 2.0 (the "License"). You may not use 112this file except in compliance with the License. You can obtain a copy 113in the file LICENSE in the source distribution or at 114L<https://www.openssl.org/source/license.html>. 115 116=cut 117
