ENCRYPT
ENCRYPT
Contains $keys[self::ENCRYPT]
Pure-PHP implementation of Triple DES.
$cfb_init_len : integer
Optimizing value while CFB-encrypting
Only relevant if $continuousBuffer enabled and $engine == self::ENGINE_MCRYPT
It's faster to re-init $enmcrypt if $buffer bytes > $cfb_init_len than using the $ecb resource furthermore.
This value depends of the chosen cipher and the time it would be needed for it's initialization [by mcrypt_generic_init()] which, typically, depends on the complexity on its internaly Key-expanding algorithm.
$ecb : resource
mcrypt resource for CFB mode
mcrypt's CFB mode, in (and only in) buffered context, is broken, so phpseclib implements the CFB mode by it self, even when the mcrypt php extension is available.
In order to do the CFB-mode work (fast) phpseclib use a separate ECB-mode mcrypt resource.
$engine : integer
Holds which crypt engine internaly should be use, which will be determined automatically on __construct()
Currently available $engines are:
setKey(string $key)
Sets the key.
Keys can be of any length. Triple DES, itself, can use 128-bit (eg. strlen($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 null bytes.
| string | $key |
_processBlock(string $block, integer $mode) : string
Encrypts or decrypts a 64-bit block
$mode should be either self::ENCRYPT or self::DECRYPT. See Feistel.png to get a general idea of what this function does.
| string | $block | |
| integer | $mode |
__construct(integer $mode = \phpseclib\Crypt\Base::MODE_CBC)
Default Constructor.
Determines whether or not the mcrypt extension should be used.
$mode could be:
\phpseclib\Crypt\Base::MODE_ECB
\phpseclib\Crypt\Base::MODE_CBC
\phpseclib\Crypt\Base::MODE_CTR
\phpseclib\Crypt\Base::MODE_CFB
\phpseclib\Crypt\Base::MODE_OFB
If not explicitly set, \phpseclib\Crypt\Base::MODE_CBC will be used.
| integer | $mode |
_openssl_ctr_process(string $plaintext, string $encryptIV, array $buffer) : string
OpenSSL CTR Processor
PHP's OpenSSL bindings do not operate in continuous mode so we'll wrap around it. Since the keystream for CTR is the same for both encrypting and decrypting this function is re-used by both Base::encrypt() and Base::decrypt(). Also, OpenSSL doesn't implement CTR for all of it's symmetric ciphers so this function will emulate CTR with ECB when necessary.
| string | $plaintext | |
| string | $encryptIV | |
| array | $buffer |
_openssl_ofb_process(string $plaintext, string $encryptIV, array $buffer) : string
OpenSSL OFB Processor
PHP's OpenSSL bindings do not operate in continuous mode so we'll wrap around it. Since the keystream for OFB is the same for both encrypting and decrypting this function is re-used by both Base::encrypt() and Base::decrypt().
| string | $plaintext | |
| string | $encryptIV | |
| array | $buffer |
enablePadding()
Pad "packets".
Block ciphers working by encrypting between their specified [$this->]block_size at a time If you ever need to encrypt or decrypt something that isn't of the proper length, it becomes necessary to pad the input so that it is of the proper length.
Padding is enabled by default. Sometimes, however, it is undesirable to pad strings. Such is the case in SSH, 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)
_pad(string $text) : string
Pads a string
Pads a string using the RSA PKCS padding standards so that its length is a multiple of the blocksize. $this->block_size - (strlen($text) % $this->block_size) bytes are added, each of which is equal to chr($this->block_size - (strlen($text) % $this->block_size)
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.
| string | $text |
_createInlineCryptFunction(array $cipher_code) : string
Creates the performance-optimized function for en/decrypt()
Internally for phpseclib developers:
_createInlineCryptFunction():
merge the $cipher_code [setup'ed by _setupInlineCrypt()] with the current [$this->]mode of operation code
create the $inline function, which called by encrypt() / decrypt() as its replacement to speed up the en/decryption operations.
return the name of the created $inline callback function
used to speed up en/decryption
The main reason why can speed up things [up to 50%] this way are:
using variables more effective then regular. (ie no use of expensive arrays but integers $k_0, $k_1 ... or even, for example, the pure $key[] values hardcoded)
avoiding 1000's of function calls of ie _encryptBlock() but inlining the crypt operations. in the mode of operation for() loop.
full loop unroll the (sometimes key-dependent) rounds avoiding this way ++$i counters and runtime-if's etc...
The basic code architectur of the generated $inline en/decrypt() lambda function, in pseudo php, is:
+----------------------------------------------------------------------------------------------+ |
callback $inline = create_function: | lambda_function_0001_crypt_ECB($action, $text) | { | INSERT PHP CODE OF: | $cipher_code['init_crypt']; // general init code. | // ie: $sbox'es declarations used for | // encrypt and decrypt'ing. | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| switch ($action) { | |||||||||||||
| case 'encrypt': | |||||||||||||
| INSERT PHP CODE OF: | |||||||||||||
| $cipher_code['init_encrypt']; // encrypt sepcific init code. | |||||||||||||
| ie: specified $key or $box | |||||||||||||
| declarations for encrypt'ing. | |||||||||||||
| foreach ($ciphertext) { | |||||||||||||
| $in = $block_size of $ciphertext; | |||||||||||||
| INSERT PHP CODE OF: | |||||||||||||
| $cipher_code['encrypt_block']; // encrypt's (string) $in, which is always: | |||||||||||||
| // strlen($in) == $this->block_size | |||||||||||||
| // here comes the cipher algorithm in action | |||||||||||||
| // for encryption. | |||||||||||||
| // $cipher_code['encrypt_block'] has to | |||||||||||||
| // encrypt the content of the $in variable | |||||||||||||
| $plaintext .= $in; | |||||||||||||
| } | |||||||||||||
| return $plaintext; | |||||||||||||
| case 'decrypt': | |||||||||||||
| INSERT PHP CODE OF: | |||||||||||||
| $cipher_code['init_decrypt']; // decrypt sepcific init code | |||||||||||||
| ie: specified $key or $box | |||||||||||||
| declarations for decrypt'ing. | |||||||||||||
| foreach ($plaintext) { | |||||||||||||
| $in = $block_size of $plaintext; | |||||||||||||
| INSERT PHP CODE OF: | |||||||||||||
| $cipher_code['decrypt_block']; // decrypt's (string) $in, which is always | |||||||||||||
| // strlen($in) == $this->block_size | |||||||||||||
| // here comes the cipher algorithm in action | |||||||||||||
| // for decryption. | |||||||||||||
| // $cipher_code['decrypt_block'] has to | |||||||||||||
| // decrypt the content of the $in variable | |||||||||||||
| $ciphertext .= $in; | |||||||||||||
| } | |||||||||||||
| return $ciphertext; | |||||||||||||
| } | |||||||||||||
| } |
+----------------------------------------------------------------------------------------------+
See also the \phpseclib\Crypt*::_setupInlineCrypt()'s for productive inline $cipher_code's how they works.
Structure of:
$cipher_code = array(
'init_crypt' => (string) '', // optional
'init_encrypt' => (string) '', // optional
'init_decrypt' => (string) '', // optional
'encrypt_block' => (string) '', // required
'decrypt_block' => (string) '' // required
);
| array | $cipher_code |
(the name of the created callback function)
_getLambdaFunctions() : array
Holds the lambda_functions table (classwide)
Each name of the lambda function, created from _setupInlineCrypt() && _createInlineCryptFunction() is stored, classwide (!), here for reusing.
The string-based index of $function is a classwide unique value representing, at least, the $mode of operation (or more... depends of the optimizing level) for which $mode the lambda function was created.
&$functions
enableContinuousBuffer()
Treat consecutive "packets" as if they are a continuous buffer.
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 \phpseclib\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.