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 16L<B<EVP_Seal>I<...>|EVP_SealInit(3)> and L<B<EVP_Open>I<...>|EVP_OpenInit(3)> 17provide public key encryption and decryption to implement digital "envelopes". 18 19The L<B<EVP_DigestSign>I<...>|EVP_DigestSignInit(3)> and 20L<B<EVP_DigestVerify>I<...>|EVP_DigestVerifyInit(3)> functions implement 21digital signatures and Message Authentication Codes (MACs). Also see the older 22L<B<EVP_Sign>I<...>|EVP_SignInit(3)> and L<B<EVP_Verify>I<...>|EVP_VerifyInit(3)> 23functions. 24 25Symmetric encryption is available with the L<B<EVP_Encrypt>I<...>|EVP_EncryptInit(3)> 26functions. The L<B<EVP_Digest>I<...>|EVP_DigestInit(3)> functions provide message digests. 27 28The B<EVP_PKEY>I<...> functions provide a high level interface to 29asymmetric algorithms. To create a new EVP_PKEY see 30L<EVP_PKEY_new(3)|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_set1_RSA(3)|EVP_PKEY_set1_RSA(3)> page, or 33new keys can be generated using L<EVP_PKEY_keygen(3)|EVP_PKEY_keygen(3)>. 34EVP_PKEYs can be compared using L<EVP_PKEY_cmp(3)|EVP_PKEY_cmp(3)>, or printed using 35L<EVP_PKEY_print_private(3)|EVP_PKEY_print_private(3)>. 36 37The EVP_PKEY functions support the full range of asymmetric algorithm operations: 38 39=over 40 41=item For key agreement see L<EVP_PKEY_derive(3)|EVP_PKEY_derive(3)> 42 43=item For signing and verifying see L<EVP_PKEY_sign(3)|EVP_PKEY_sign(3)>, 44L<EVP_PKEY_verify(3)|EVP_PKEY_verify(3)> and L<EVP_PKEY_verify_recover(3)|EVP_PKEY_verify_recover(3)>. 45However, note that 46these functions do not perform a digest of the data to be signed. Therefore 47normally you would use the L<B<EVP_DigestSign>I<...>|EVP_DigestSignInit(3)> 48functions for this purpose. 49 50=item For encryption and decryption see L<EVP_PKEY_encrypt(3)|EVP_PKEY_encrypt(3)> 51and L<EVP_PKEY_decrypt(3)|EVP_PKEY_decrypt(3)> respectively. However, note that 52these functions perform encryption and decryption only. As public key 53encryption is an expensive operation, normally you would wrap 54an encrypted message in a "digital envelope" using the L<B<EVP_Seal>I<...>|EVP_SealInit(3)> and 55L<B<EVP_Open>I<...>|EVP_OpenInit(3)> functions. 56 57=back 58 59The L<EVP_BytesToKey(3)|EVP_BytesToKey(3)> function provides some limited support for password 60based encryption. Careful selection of the parameters will provide a PKCS#5 PBKDF1 compatible 61implementation. However, new applications should not typically use this (preferring, for example, 62PBKDF2 from PCKS#5). 63 64Algorithms are loaded with L<OpenSSL_add_all_algorithms(3)|OpenSSL_add_all_algorithms(3)>. 65 66All the symmetric algorithms (ciphers), digests and asymmetric algorithms 67(public key algorithms) can be replaced by L<ENGINE|engine(3)> modules providing alternative 68implementations. If ENGINE implementations of ciphers or digests are registered 69as defaults, then the various EVP functions will automatically use those 70implementations automatically in preference to built in software 71implementations. For more information, consult the engine(3) man page. 72 73Although low level algorithm specific functions exist for many algorithms 74their use is discouraged. They cannot be used with an ENGINE and ENGINE 75versions of new algorithms cannot be accessed using the low level functions. 76Also makes code harder to adapt to new algorithms and some options are not 77cleanly supported at the low level and some operations are more efficient 78using the high level interface. 79 80=head1 SEE ALSO 81 82L<EVP_DigestInit(3)|EVP_DigestInit(3)>, 83L<EVP_EncryptInit(3)|EVP_EncryptInit(3)>, 84L<EVP_OpenInit(3)|EVP_OpenInit(3)>, 85L<EVP_SealInit(3)|EVP_SealInit(3)>, 86L<EVP_DigestSignInit(3)|EVP_DigestSignInit(3)>, 87L<EVP_SignInit(3)|EVP_SignInit(3)>, 88L<EVP_VerifyInit(3)|EVP_VerifyInit(3)>, 89L<EVP_PKEY_new(3)|EVP_PKEY_new(3)>, 90L<EVP_PKEY_set1_RSA(3)|EVP_PKEY_set1_RSA(3)>, 91L<EVP_PKEY_keygen(3)|EVP_PKEY_keygen(3)>, 92L<EVP_PKEY_print_private(3)|EVP_PKEY_print_private(3)>, 93L<EVP_PKEY_decrypt(3)|EVP_PKEY_decrypt(3)>, 94L<EVP_PKEY_encrypt(3)|EVP_PKEY_encrypt(3)>, 95L<EVP_PKEY_sign(3)|EVP_PKEY_sign(3)>, 96L<EVP_PKEY_verify(3)|EVP_PKEY_verify(3)>, 97L<EVP_PKEY_verify_recover(3)|EVP_PKEY_verify_recover(3)>, 98L<EVP_PKEY_derive(3)|EVP_PKEY_derive(3)>, 99L<EVP_BytesToKey(3)|EVP_BytesToKey(3)>, 100L<OpenSSL_add_all_algorithms(3)|OpenSSL_add_all_algorithms(3)>, 101L<engine(3)|engine(3)> 102 103=cut 104