5 evp - high-level cryptographic functions
9 #include <openssl/evp.h>
13 The EVP library provides a high-level interface to cryptographic
16 L<B<EVP_Seal>I<...>|EVP_SealInit(3)> and L<B<EVP_Open>I<...>|EVP_OpenInit(3)>
17 provide public key encryption and decryption to implement digital "envelopes".
19 The L<B<EVP_DigestSign>I<...>|EVP_DigestSignInit(3)> and
20 L<B<EVP_DigestVerify>I<...>|EVP_DigestVerifyInit(3)> functions implement
21 digital signatures and Message Authentication Codes (MACs). Also see the older
22 L<B<EVP_Sign>I<...>|EVP_SignInit(3)> and L<B<EVP_Verify>I<...>|EVP_VerifyInit(3)>
25 Symmetric encryption is available with the L<B<EVP_Encrypt>I<...>|EVP_EncryptInit(3)>
26 functions. The L<B<EVP_Digest>I<...>|EVP_DigestInit(3)> functions provide message digests.
28 The B<EVP_PKEY>I<...> functions provide a high level interface to
29 asymmetric algorithms. To create a new EVP_PKEY see
30 L<EVP_PKEY_new(3)|EVP_PKEY_new(3)>. EVP_PKEYs can be associated
31 with a private key of a particular algorithm by using the functions
32 described on the L<EVP_PKEY_set1_RSA(3)|EVP_PKEY_set1_RSA(3)> page, or
33 new keys can be generated using L<EVP_PKEY_keygen(3)|EVP_PKEY_keygen(3)>.
34 EVP_PKEYs can be compared using L<EVP_PKEY_cmp(3)|EVP_PKEY_cmp(3)>, or printed using
35 L<EVP_PKEY_print_private(3)|EVP_PKEY_print_private(3)>.
37 The EVP_PKEY functions support the full range of asymmetric algorithm operations:
40 =item For key agreement see L<EVP_PKEY_derive(3)|EVP_PKEY_derive(3)>
42 =item For signing and verifying see L<EVP_PKEY_sign(3)|EVP_PKEY_sign(3)>,
43 L<EVP_PKEY_verify(3)|EVP_PKEY_verify(3)> and L<EVP_PKEY_verify_recover(3)|EVP_PKEY_verify_recover(3)>.
45 these functions do not perform a digest of the data to be signed. Therefore
46 normally you would use the L<B<EVP_DigestSign>I<...>|EVP_DigestSignInit(3)>
47 functions for this purpose.
49 =item For encryption and decryption see L<EVP_PKEY_encrypt(3)|EVP_PKEY_encrypt(3)>
50 and L<EVP_PKEY_decrypt(3)|EVP_PKEY_decrypt(3)> respectively. However, note that
51 these functions perform encryption and decryption only. As public key
52 encryption is an expensive operation, normally you would wrap
53 an encrypted message in a "digital envelope" using the L<B<EVP_Seal>I<...>|EVP_SealInit(3)> and
54 L<B<EVP_Open>I<...>|EVP_OpenInit(3)> functions.
58 The L<EVP_BytesToKey(3)|EVP_BytesToKey(3)> function provides some limited support for password
59 based encryption. Careful selection of the parameters will provide a PKCS#5 PBKDF1 compatible
60 implementation. However, new applications should not typically use this (preferring, for example,
63 Algorithms are loaded with L<OpenSSL_add_all_algorithms(3)|OpenSSL_add_all_algorithms(3)>.
65 All the symmetric algorithms (ciphers), digests and asymmetric algorithms
66 (public key algorithms) can be replaced by L<ENGINE|engine(3)> modules providing alternative
67 implementations. If ENGINE implementations of ciphers or digests are registered
68 as defaults, then the various EVP functions will automatically use those
69 implementations automatically in preference to built in software
70 implementations. For more information, consult the engine(3) man page.
72 Although low level algorithm specific functions exist for many algorithms
73 their use is discouraged. They cannot be used with an ENGINE and ENGINE
74 versions of new algorithms cannot be accessed using the low level functions.
75 Also makes code harder to adapt to new algorithms and some options are not
76 cleanly supported at the low level and some operations are more efficient
77 using the high level interface.
81 L<EVP_DigestInit(3)|EVP_DigestInit(3)>,
82 L<EVP_EncryptInit(3)|EVP_EncryptInit(3)>,
83 L<EVP_OpenInit(3)|EVP_OpenInit(3)>,
84 L<EVP_SealInit(3)|EVP_SealInit(3)>,
85 L<EVP_DigestSignInit(3)|EVP_DigestSignInit(3)>,
86 L<EVP_SignInit(3)|EVP_SignInit(3)>,
87 L<EVP_VerifyInit(3)|EVP_VerifyInit(3)>,
88 L<EVP_PKEY_new(3)|EVP_PKEY_new(3)>,
89 L<EVP_PKEY_set1_RSA(3)|EVP_PKEY_set1_RSA(3)>,
90 L<EVP_PKEY_keygen(3)|EVP_PKEY_keygen(3)>,
91 L<EVP_PKEY_print_private(3)|EVP_PKEY_print_private(3)>,
92 L<EVP_PKEY_decrypt(3)|EVP_PKEY_decrypt(3)>,
93 L<EVP_PKEY_encrypt(3)|EVP_PKEY_encrypt(3)>,
94 L<EVP_PKEY_sign(3)|EVP_PKEY_sign(3)>,
95 L<EVP_PKEY_verify(3)|EVP_PKEY_verify(3)>,
96 L<EVP_PKEY_verify_recover(3)|EVP_PKEY_verify_recover(3)>,
97 L<EVP_PKEY_derive(3)|EVP_PKEY_derive(3)>,
98 L<EVP_BytesToKey(3)|EVP_BytesToKey(3)>,
99 L<OpenSSL_add_all_algorithms(3)|OpenSSL_add_all_algorithms(3)>,
100 L<engine(3)|engine(3)>