evp.pod revision 298999 
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
16B<EVP_Seal>I<...> and B<EVP_Open>I<...> provide public key encryption
17and decryption to implement digital "envelopes".
18
19The B<EVP_Sign>I<...> and B<EVP_Verify>I<...> functions implement
20digital signatures.
21
22Symmetric encryption is available with the B<EVP_Encrypt>I<...>
23functions.  The B<EVP_Digest>I<...> functions provide message digests.
24
25The B<EVP_PKEY>I<...> functions provide a high level interface to
26asymmetric algorithms.
27
28The L<B<EVP_Encode>I<...>|EVP_EncodeInit(3)> and
29L<B<EVP_Decode>I<...>|EVP_EncodeInit(3)> functions implement base 64 encoding
30and decoding.
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32Algorithms are loaded with OpenSSL_add_all_algorithms(3).
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34All the symmetric algorithms (ciphers), digests and asymmetric algorithms
35(public key algorithms) can be replaced by ENGINE modules providing alternative
36implementations. If ENGINE implementations of ciphers or digests are registered
37as defaults, then the various EVP functions will automatically use those
38implementations automatically in preference to built in software
39implementations. For more information, consult the engine(3) man page.
40
41Although low level algorithm specific functions exist for many algorithms
42their use is discouraged. They cannot be used with an ENGINE and ENGINE
43versions of new algorithms cannot be accessed using the low level functions.
44Also makes code harder to adapt to new algorithms and some options are not 
45cleanly supported at the low level and some operations are more efficient
46using the high level interface.
47
48=head1 SEE ALSO
49
50L<EVP_DigestInit(3)|EVP_DigestInit(3)>,
51L<EVP_EncryptInit(3)|EVP_EncryptInit(3)>,
52L<EVP_OpenInit(3)|EVP_OpenInit(3)>,
53L<EVP_SealInit(3)|EVP_SealInit(3)>,
54L<EVP_SignInit(3)|EVP_SignInit(3)>,
55L<EVP_VerifyInit(3)|EVP_VerifyInit(3)>,
56L<EVP_EncodeInit(3)>,
57L<OpenSSL_add_all_algorithms(3)|OpenSSL_add_all_algorithms(3)>,
58L<engine(3)|engine(3)>
59
60=cut
61