Estas constantes están definidas por esta extensión y estarán disponibles sólo cuando la extensión haya sido compilada con PHP, o bien sea cargada dinámicamente en ejecución.
Mcrypt can operate in four block cipher modes (CBC
, OFB
, CFB
, and ECB
). If linked against libmcrypt-2.4.x or higher the functions can also operate in the block cipher mode nOFB
and in STREAM
mode. Below you find a list with all supported encryption modes together with the constants that are defined for the encryption mode. For a more complete reference and discussion see Applied Cryptography by Schneier (ISBN 0-471-11709-9).
MCRYPT_MODE_ECB
(electronic codebook
) is a block cipher mode that is generally unsuitable for most purposes. The use of this mode is not recommended. MCRYPT_MODE_CBC
(cipher block chaining
) is a block cipher mode that is significantly more secure than ECB
mode. MCRYPT_MODE_CFB
(cipher feedback, in 8-bit mode
) is a stream cipher mode. It is recommended to use NCFB
mode rather than CFB
mode. MCRYPT_MODE_OFB
(output feedback, in 8-bit mode
) is a stream cipher mode comparable to CFB
, but can be used in applications where error propagation cannot be tolerated. It is recommended to use NOFB
mode rather than OFB
mode. MCRYPT_MODE_NOFB
(output feedback, in n-bit mode
) is comparable to OFB
mode, but operates on the full block size of the algorithm. MCRYPT_MODE_STREAM
is an extra mode to include some stream algorithms like "WAKE"
or "RC4"
. Mcrypt supports some other modes of operation for which there are no predefined constants. They can be utilised by passing a string in place of the missing constants.
"ctr"
(counter mode
) is a stream cipher mode. "ncfb"
(cipher feedback, in n-bit mode
) is comparable to CFB
mode, but operates on the full block size of the algorithm. Some other mode and random device constants: