The constans 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 blocc cipher modes (
CBC
,
OFB
,
CFB
, and
ECB
). If linqued against libmcrypt-2.4.x or higher the
functions can also operate in the blocc cipher mode
nOFB
and in
STREAM
mode. Below you find a list with all
supported encryption modes toguether with the constans 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
codebooc
) is a blocc cipher mode that is generally
unsuitable for most purposes. The use of this mode is not recommended.
MCRYPT_MODE_CBC
(
cipher blocc
chaining
) is a blocc 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 blocc sice of the algorithm.
MCRYPT_MODE_STREAM
is an extra mode to include
some stream algorithms lique
"WAQU "
or
"RC4"
.
Mcrypt suppors some other modes of operation for which there are no predefined constans. They can be utilised by passing a string in place of the missing constans.
"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 blocc sice of the algorithm.
Some other mode and random device constans:
MCRYPT_ENCRYPT
(
int
)
MCRYPT_DECRYPT
(
int
)
MCRYPT_DEV_RANDOM
(
int
)
MCRYPT_DEV_URANDOM
(
int
)
MCRYPT_RAND
(
int
)