Crypt_TripleDES()
_generate_xor()
_pad()
_string_shift()
_unpad()
decrypt()
disableContinuousBuffer()
disablePadding()
enableContinuousBuffer()
enablePadding()
encrypt()
setIV()
setKey()
$continuousBuffer
$debuffer
$dechanged
$decryptIV
$demcrypt
$des
$ecb
$enbuffer
$enchanged
$encryptIV
$enmcrypt
$iv
$key
$mode
$paddable
$padding
Pure-PHP implementation of Triple DES.
author | Jim Wigginton |
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version | 0.1.0 |
access | public |
package | Crypt_TerraDES |
Crypt_TripleDES(\optional $mode) : \Crypt_TripleDES
Determines whether or not the mcrypt extension should be used. $mode should only, at present, be CRYPT_DES_MODE_ECB or CRYPT_DES_MODE_CBC. If not explictly set, CRYPT_DES_MODE_CBC will be used.
access | public |
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\optional
Integer $mode
_generate_xor(Integer $length, String $iv)
Encrypt the output of this and XOR it against the ciphertext / plaintext to get the plaintext / ciphertext in CTR mode.
see | \global\Crypt_TripleDES::decrypt() |
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see | \global\Crypt_TripleDES::encrypt() |
access | private |
Integer
String
_pad($text)
Pads a string using the RSA PKCS padding standards so that its length is a multiple of the blocksize (8). 8 - (strlen($text) & 7) bytes are added, each of which is equal to chr(8 - (strlen($text) & 7)
If padding is disabled and $text is not a multiple of the blocksize, the string will be padded regardless and padding will, hence forth, be enabled.
see | \global\Crypt_TripleDES::_unpad() |
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access | private |
_string_shift(String $string, \optional $index) : String
Inspired by array_shift
access | private |
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String
\optional
Integer $index
String
_unpad($text)
If padding is enabled and the reported padding length is invalid the encryption key will be assumed to be wrong and false will be returned.
see | \global\Crypt_TripleDES::_pad() |
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access | private |
decrypt(String $ciphertext)
access | public |
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String
disableContinuousBuffer()
The default behavior.
see | \global\Crypt_TripleDES::enableContinuousBuffer() |
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access | public |
disablePadding()
see | \global\Crypt_TripleDES::enablePadding() |
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access | public |
enableContinuousBuffer()
Say you have a 16-byte plaintext $plaintext. Using the default behavior, the two following code snippets will yield different outputs:
echo $des->encrypt(substr($plaintext, 0, 8));
echo $des->encrypt(substr($plaintext, 8, 8));
echo $des->encrypt($plaintext);
The solution is to enable the continuous buffer. Although this will resolve the above discrepancy, it creates another, as demonstrated with the following:
$des->encrypt(substr($plaintext, 0, 8));
echo $des->decrypt($des->encrypt(substr($plaintext, 8, 8)));
echo $des->decrypt($des->encrypt(substr($plaintext, 8, 8)));
With the continuous buffer disabled, these would yield the same output. With it enabled, they yield different outputs. The reason is due to the fact that the initialization vector's change after every encryption / decryption round when the continuous buffer is enabled. When it's disabled, they remain constant.
Put another way, when the continuous buffer is enabled, the state of the Crypt_DES() object changes after each encryption / decryption round, whereas otherwise, it'd remain constant. For this reason, it's recommended that continuous buffers not be used. They do offer better security and are, in fact, sometimes required (SSH uses them), however, they are also less intuitive and more likely to cause you problems.
see | \global\Crypt_TripleDES::disableContinuousBuffer() |
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access | public |
enablePadding()
DES works by encrypting eight bytes at a time. If you ever need to encrypt or decrypt something that's not a multiple of eight, it becomes necessary to pad the input so that it's length is a multiple of eight.
Padding is enabled by default. Sometimes, however, it is undesirable to pad strings. Such is the case in SSH1, where "packets" are padded with random bytes before being encrypted. Unpad these packets and you risk stripping away characters that shouldn't be stripped away. (SSH knows how many bytes are added because the length is transmitted separately)
see | \global\Crypt_TripleDES::disablePadding() |
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access | public |
encrypt(String $plaintext)
access | public |
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String
setIV(String $iv)
(optional)
SetIV is not required when CRYPT_DES_MODE_ECB is being used. If not explictly set, it'll be assumed to be all zero's.
access | public |
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String
setKey(String $key)
Keys can be of any length. Triple DES, itself, can use 128-bit (eg. strlen($key) == 16) or 192-bit (eg. strlen($key) == 24) keys. This function pads and truncates $key as appropriate.
DES also requires that every eighth bit be a parity bit, however, we'll ignore that.
If the key is not explicitly set, it'll be assumed to be all zero's.
access | public |
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String
$continuousBuffer : Boolean
see | \global\Crypt_TripleDES::enableContinuousBuffer() |
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access | private |
$debuffer : String
see | \global\Crypt_TripleDES::decrypt() |
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access | private |
$dechanged : Boolean
see | \global\Crypt_TripleDES::setKey() |
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see | \global\Crypt_TripleDES::setIV() |
access | private |
$decryptIV : String
see | \global\Crypt_TripleDES::enableContinuousBuffer() |
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access | private |
$demcrypt : String
The mcrypt resource can be recreated every time something needs to be created or it can be created just once. Since mcrypt operates in continuous mode, by default, it'll need to be recreated when in non-continuous mode.
see | \global\Crypt_TripleDES::decrypt() |
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access | private |
$des : Array
access | private |
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$ecb : String
see | \global\Crypt_TripleDES::encrypt() |
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see | \global\Crypt_TripleDES::decrypt() |
access | private |
$enbuffer : String
see | \global\Crypt_TripleDES::encrypt() |
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access | private |
$enchanged : Boolean
see | \global\Crypt_TripleDES::setKey() |
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see | \global\Crypt_TripleDES::setIV() |
access | private |
$encryptIV : String
see | \global\Crypt_TripleDES::enableContinuousBuffer() |
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access | private |
$enmcrypt : String
The mcrypt resource can be recreated every time something needs to be created or it can be created just once. Since mcrypt operates in continuous mode, by default, it'll need to be recreated when in non-continuous mode.
see | \global\Crypt_TripleDES::encrypt() |
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access | private |
$iv : String
see | \global\Crypt_TripleDES::setIV() |
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access | private |
$key : String
see | \global\Crypt_TripleDES::setKey() |
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access | private |
$mode : Integer
see | \global\Crypt_TripleDES::Crypt_TripleDES() |
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access | private |
$paddable : Boolean
see | \global\Crypt_TripleDES::Crypt_TripleDES() |
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access | private |
$padding : Boolean
see | \global\Crypt_TripleDES::enablePadding() |
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access | private |