evp(3)

evp(3)                       OpenSSL                       evp(3)

NAME

     evp - high-level cryptographic functions

SYNOPSIS

      #include <openssl/evp.h>

DESCRIPTION

     The EVP library provides a high-level interface to
     cryptographic functions.

     EVP_Seal... and EVP_Open...  provide public key encryption
     and decryption to implement digital "envelopes".

     The EVP_DigestSign... and EVP_DigestVerify... functions
     implement digital signatures and Message Authentication
     Codes (MACs). Also see the older EVP_Sign... and
     EVP_Verify...  functions.

     Symmetric encryption is available with the EVP_Encrypt...
     functions.  The EVP_Digest... functions provide message
     digests.

     The EVP_PKEY... functions provide a high level interface to
     asymmetric algorithms. To create a new EVP_PKEY see
     EVP_PKEY_new(3). EVP_PKEYs can be associated with a private
     key of a particular algorithm by using the functions
     described on the EVP_PKEY_set1_RSA(3) page, or new keys can
     be generated using EVP_PKEY_keygen(3).  EVP_PKEYs can be
     compared using EVP_PKEY_cmp(3), or printed using
     EVP_PKEY_print_private(3).

     The EVP_PKEY functions support the full range of asymmetric
     algorithm operations:

     For key agreement see EVP_PKEY_derive(3)
EVP_PKEY_verify(3) and 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 EVP_DigestSign...

functions for this purpose.
     For signing and verifying see EVP_PKEY_sign(3),
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 EVP_Seal...

and EVP_Open... functions.

     For encryption and decryption see EVP_PKEY_encrypt(3) and

     The 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

1.0.2t               Last change: 2019-09-10                    1

evp(3)                       OpenSSL                       evp(3)

     PCKS#5).

     The EVP_Encode... and EVP_Decode... functions implement base
     64 encoding and decoding.

     Algorithms are loaded with OpenSSL_add_all_algorithms(3).

     All the symmetric algorithms (ciphers), digests and
     asymmetric algorithms (public key algorithms) can be
     replaced by ENGINE 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
     implementations. For more information, consult the engine(3)
     man page.

     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 cleanly supported at the low level and some
     operations are more efficient using the high level
     interface.

SEE ALSO

     EVP_DigestInit(3), EVP_EncryptInit(3), EVP_OpenInit(3),
     EVP_SealInit(3), EVP_DigestSignInit(3), EVP_SignInit(3),
     EVP_VerifyInit(3), EVP_EncodeInit(3), EVP_PKEY_new(3),
     EVP_PKEY_set1_RSA(3), EVP_PKEY_keygen(3),
     EVP_PKEY_print_private(3), EVP_PKEY_decrypt(3),
     EVP_PKEY_encrypt(3), EVP_PKEY_sign(3), EVP_PKEY_verify(3),
     EVP_PKEY_verify_recover(3), EVP_PKEY_derive(3),
     EVP_BytesToKey(3), OpenSSL_add_all_algorithms(3), engine(3)

1.0.2t               Last change: 2019-09-10                    2