=pod
+=for comment openssl_manual_section:7
+
=head1 NAME
evp - high-level cryptographic functions
The EVP library provides a high-level interface to cryptographic
functions.
-B<EVP_Seal>I<...> and B<EVP_Open>I<...> provide public key encryption
-and decryption to implement digital "envelopes".
+L<B<EVP_Seal>I<...>|EVP_SealInit(3)> and L<B<EVP_Open>I<...>|EVP_OpenInit(3)>
+provide public key encryption and decryption to implement digital "envelopes".
-The B<EVP_Sign>I<...> and B<EVP_Verify>I<...> functions implement
-digital signatures.
+The L<B<EVP_DigestSign>I<...>|EVP_DigestSignInit(3)> and
+L<B<EVP_DigestVerify>I<...>|EVP_DigestVerifyInit(3)> functions implement
+digital signatures and Message Authentication Codes (MACs). Also see the older
+L<B<EVP_Sign>I<...>|EVP_SignInit(3)> and L<B<EVP_Verify>I<...>|EVP_VerifyInit(3)>
+functions.
-Symmetric encryption is available with the B<EVP_Encrypt>I<...>
-functions. The B<EVP_Digest>I<...> functions provide message digests.
+Symmetric encryption is available with the L<B<EVP_Encrypt>I<...>|EVP_EncryptInit(3)>
+functions. The L<B<EVP_Digest>I<...>|EVP_DigestInit(3)> functions provide message digests.
The B<EVP_PKEY>I<...> functions provide a high level interface to
-asymmetric algorithms.
+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
+
+=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).
-Algorithms are loaded with OpenSSL_add_all_algorithms(3).
+The L<B<EVP_Encode>I<...>|EVP_EncodeInit(3)> and
+L<B<EVP_Decode>I<...>|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
+(public key algorithms) can be replaced by L<engine(3)> 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
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
+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)|EVP_DigestInit(3)>,
-L<EVP_EncryptInit(3)|EVP_EncryptInit(3)>,
-L<EVP_OpenInit(3)|EVP_OpenInit(3)>,
-L<EVP_SealInit(3)|EVP_SealInit(3)>,
-L<EVP_SignInit(3)|EVP_SignInit(3)>,
-L<EVP_VerifyInit(3)|EVP_VerifyInit(3)>,
-L<OpenSSL_add_all_algorithms(3)|OpenSSL_add_all_algorithms(3)>,
-L<engine(3)|engine(3)>
+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(3)>
+
+=head1 COPYRIGHT
+
+Copyright 2000-2016 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
projects / cassiopeia.git / blobdiff