Predefined Constants
The constants below are defined by this extension, and will only be available when the extension has either been compiled into PHP or dynamically loaded at runtime.
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 thanECB
mode. -
MCRYPT_MODE_CFB
(cipher feedback, in 8-bit mode
) is a stream cipher mode. It is recommended to useNCFB
mode rather thanCFB
mode. -
MCRYPT_MODE_OFB
(output feedback, in 8-bit mode
) is a stream cipher mode comparable toCFB
, but can be used in applications where error propagation cannot be tolerated. It is recommended to useNOFB
mode rather thanOFB
mode. -
MCRYPT_MODE_NOFB
(output feedback, in n-bit mode
) is comparable toOFB
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 toCFB
mode, but operates on the full block size of the algorithm.
Some other mode and random device constants:
-
MCRYPT_ENCRYPT
(int) -
MCRYPT_DECRYPT
(int) -
MCRYPT_DEV_RANDOM
(int) -
MCRYPT_DEV_URANDOM
(int) -
MCRYPT_RAND
(int)