Crypt_RC4
class Crypt_RC4 extends Crypt_Base (View source)
Pure-PHP implementation of RC4.
Properties
int | $mode | The Encryption Mode | from Crypt_Base |
int | $block_size | Block Length of the cipher | |
string | $key | The Key | |
string | $iv | The Initialization Vector | from Crypt_Base |
string | $encryptIV | A "sliding" Initialization Vector | from Crypt_Base |
string | $decryptIV | A "sliding" Initialization Vector | from Crypt_Base |
bool | $continuousBuffer | Continuous Buffer status | from Crypt_Base |
array | $enbuffer | Encryption buffer for CTR, OFB and CFB modes | from Crypt_Base |
array | $debuffer | Decryption buffer for CTR, OFB and CFB modes | from Crypt_Base |
resource | $enmcrypt | mcrypt resource for encryption | from Crypt_Base |
resource | $demcrypt | mcrypt resource for decryption | from Crypt_Base |
bool | $enchanged | Does the enmcrypt resource need to be (re)initialized? | from Crypt_Base |
bool | $dechanged | Does the demcrypt resource need to be (re)initialized? | from Crypt_Base |
resource | $ecb | mcrypt resource for CFB mode | from Crypt_Base |
int | $cfb_init_len | Optimizing value while CFB-encrypting | from Crypt_Base |
bool | $changed | Does internal cipher state need to be (re)initialized? | from Crypt_Base |
bool | $padding | Padding status | from Crypt_Base |
bool | $paddable | Is the mode one that is paddable? | from Crypt_Base |
int | $engine | Holds which crypt engine internaly should be use, which will be determined automatically on __construct() | from Crypt_Base |
int | $preferredEngine | Holds the preferred crypt engine | from Crypt_Base |
string | $cipher_name_mcrypt | The mcrypt specific name of the cipher | |
string | $cipher_name_openssl | The openssl specific name of the cipher | from Crypt_Base |
string | $cipher_name_openssl_ecb | The openssl specific name of the cipher in ECB mode | from Crypt_Base |
string | $password_default_salt | The default salt used by setPassword() | from Crypt_Base |
string | $const_namespace | The namespace used by the cipher for its constants. | |
callable | $inline_crypt | The name of the performance-optimized callback function | from Crypt_Base |
mixed | $use_inline_crypt | Holds whether performance-optimized $inline_crypt() can/should be used. | |
bool | $openssl_emulate_ctr | If OpenSSL can be used in ECB but not in CTR we can emulate CTR | from Crypt_Base |
mixed | $openssl_options | Determines what options are passed to openssl_encrypt/decrypt | from Crypt_Base |
bool | $explicit_key_length | Has the key length explicitly been set or should it be derived from the key, itself? | from Crypt_Base |
bool | $skip_key_adjustment | Don't truncate / null pad key | from Crypt_Base |
int | $key_length | Key Length (in bytes) | |
array | $stream | The Key Stream for decryption and encryption |
Methods
Default Constructor.
Dummy function.
Sets the key length
Encrypts a message.
Decrypts a message.
OpenSSL CTR Processor
OpenSSL OFB Processor
Treat consecutive "packets" as if they are a continuous buffer.
Treat consecutive packets as if they are a discontinuous buffer.
Test for engine validity
Setup the key (expansion)
Creates the performance-optimized function for en/decrypt()
PHP4 compatible Default Constructor.
Encrypts or decrypts a message.
Details
__construct()
Default Constructor.
Determines whether or not the mcrypt extension should be used.
Crypt_Base(int $mode = CRYPT_MODE_CBC)
PHP4 compatible Default Constructor.
setIV(string $iv)
Dummy function.
Some protocols, such as WEP, prepend an "initialization vector" to the key, effectively creating a new key [1]. If you need to use an initialization vector in this manner, feel free to prepend it to the key, yourself, before calling setKey().
[1] WEP's initialization vectors (IV's) are used in a somewhat insecure way. Since, in that protocol, the IV's are relatively easy to predict, an attack described by {@link http://www.drizzle.com/~aboba/IEEE/rc4_ksaproc.pdf Scott Fluhrer, Itsik Mantin, and Adi Shamir} can be used to quickly guess at the rest of the key. The following links elaborate:
{@link http://www.rsa.com/rsalabs/node.asp?id=2009 http://www.rsa.com/rsalabs/node.asp?id=2009} {@link http://en.wikipedia.org/wiki/Related_key_attack http://en.wikipedia.org/wiki/Related_key_attack}
setKeyLength(int $length)
Sets the key length
Keys can be between 1 and 256 bytes long.
int
getKeyLength()
Returns the current key length in bits
int
getBlockLength()
Returns the current block length in bits
setKey(string $key)
Sets the key.
The min/max length(s) of the key depends on the cipher which is used. If the key not fits the length(s) of the cipher it will paded with null bytes up to the closest valid key length. If the key is more than max length, we trim the excess bits.
If the key is not explicitly set, it'll be assumed to be all null bytes.
bool
setPassword(string $password, string $method = 'pbkdf2')
Sets the password.
Depending on what $method is set to, setPassword()'s (optional) parameters are as follows: {@link http://en.wikipedia.org/wiki/PBKDF2 pbkdf2} or pbkdf1: $hash, $salt, $count, $dkLen
Where $hash (default = sha1) currently supports the following hashes: see: Crypt/Hash.php
string
encrypt(string $plaintext)
Encrypts a message.
string
decrypt(string $ciphertext)
Decrypts a message.
$this->decrypt($this->encrypt($plaintext)) == $this->encrypt($this->encrypt($plaintext)). At least if the continuous buffer is disabled.
string
_openssl_ctr_process(string $plaintext, string $encryptIV, array $buffer)
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 Crypt_Base::encrypt() and Crypt_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
_openssl_ofb_process(string $plaintext, string $encryptIV, array $buffer)
OpenSSL OFB Processor
PHP's OpenSSL bindings do not operate in continuous mode so we'll wrap around it. Since the keystream for OFB is the same for both encrypting and decrypting this function is re-used by both Crypt_Base::encrypt() and Crypt_Base::decrypt().
int
_openssl_translate_mode()
phpseclib <-> OpenSSL Mode Mapper
May need to be overwritten by classes extending this one in some cases
enablePadding()
Pad "packets".
Block ciphers working by encrypting between their specified [$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)
disablePadding()
Do not pad packets.
enableContinuousBuffer()
Treat consecutive "packets" as if they are a continuous buffer.
Say you have a 32-byte plaintext $plaintext. Using the default behavior, the two following code snippets will yield different outputs:
echo $rijndael->encrypt(substr($plaintext, 0, 16));
echo $rijndael->encrypt(substr($plaintext, 16, 16));
echo $rijndael->encrypt($plaintext);
The solution is to enable the continuous buffer. Although this will resolve the above discrepancy, it creates another, as demonstrated with the following:
$rijndael->encrypt(substr($plaintext, 0, 16));
echo $rijndael->decrypt($rijndael->encrypt(substr($plaintext, 16, 16)));
echo $rijndael->decrypt($rijndael->encrypt(substr($plaintext, 16, 16)));
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_*() 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.
disableContinuousBuffer()
Treat consecutive packets as if they are a discontinuous buffer.
The default behavior.
bool
isValidEngine(int $engine)
Test for engine validity
This is mainly just a wrapper to set things up for Crypt_Base::isValidEngine()
setPreferredEngine(int $engine)
Sets the preferred crypt engine
Currently, $engine could be:
CRYPT_ENGINE_OPENSSL [very fast]
CRYPT_ENGINE_MCRYPT [fast]
CRYPT_ENGINE_INTERNAL [slow]
If the preferred crypt engine is not available the fastest available one will be used
getEngine()
Returns the engine currently being utilized
_setEngine()
Sets the engine as appropriate
string
_encryptBlock(string $in)
Encrypts a block
string
_decryptBlock(string $in)
Decrypts a block
_setupKey()
Setup the key (expansion)
_setup()
Setup the CRYPT_ENGINE_INTERNAL $engine
(re)init, if necessary, the internal cipher $engine and flush all $buffers Used (only) if $engine == CRYPT_ENGINE_INTERNAL
_setup() will be called each time if $changed === true typically this happens when using one or more of following public methods:
setKey()
setIV()
disableContinuousBuffer()
First run of encrypt() / decrypt() with no init-settings
_setupMcrypt()
Setup the CRYPT_ENGINE_MCRYPT $engine
(re)init, if necessary, the (ext)mcrypt resources and flush all $buffers Used (only) if $engine = CRYPT_ENGINE_MCRYPT
_setupMcrypt() will be called each time if $changed === true typically this happens when using one or more of following public methods:
setKey()
setIV()
disableContinuousBuffer()
First run of encrypt() / decrypt()
string
_pad(string $text)
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
_unpad(string $text)
Unpads a string.
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.
_clearBuffers()
Clears internal buffers
Clearing/resetting the internal buffers is done everytime after disableContinuousBuffer() or on cipher $engine (re)init ie after setKey() or setIV()
string
_string_shift(string $string, int $index = 1)
String Shift
Inspired by array_shift
string
_string_pop(string $string, int $index = 1)
String Pop
Inspired by array_pop
_increment_str(string $var)
Increment the current string
_setupInlineCrypt()
Setup the performance-optimized function for de/encrypt()
Stores the created (or existing) callback function-name in $this->inline_crypt
Internally for phpseclib developers:
_setupInlineCrypt() would be called only if:
- $engine == CRYPT_ENGINE_INTERNAL and
- $use_inline_crypt === true
- each time on _setup(), after(!) _setupKey()
This ensures that _setupInlineCrypt() has always a
full ready2go initializated internal cipher $engine state
where, for example, the keys allready expanded,
keys/block_size calculated and such.
It is, each time if called, the responsibility of _setupInlineCrypt():
- to set $this->inline_crypt to a valid and fully working callback function
as a (faster) replacement for encrypt() / decrypt()
- NOT to create unlimited callback functions (for memory reasons!)
no matter how often _setupInlineCrypt() would be called. At some
point of amount they must be generic re-useable.
- the code of _setupInlineCrypt() it self,
and the generated callback code,
must be, in following order:
- 100% safe
- 100% compatible to encrypt()/decrypt()
- using only php5+ features/lang-constructs/php-extensions if
compatibility (down to php4) or fallback is provided
- readable/maintainable/understandable/commented and... not-cryptic-styled-code :-)
- >= 10% faster than encrypt()/decrypt() [which is, by the way,
the reason for the existence of _setupInlineCrypt() :-)]
- memory-nice
- short (as good as possible)
Note: - setupInlineCrypt() is using _createInlineCryptFunction() to create the full callback function code. - In case of using inline crypting, _setupInlineCrypt() must extend by the child Crypt* class. - The following variable names are reserved: - $_* (all variable names prefixed with an underscore) - $self (object reference to it self. Do not use $this, but $self instead) - $in (the content of $in has to en/decrypt by the generated code) - The callback function should not use the 'return' statement, but en/decrypt'ing the content of $in only
string
_createInlineCryptFunction(array $cipher_code)
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 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
_getLambdaFunctions()
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.
string
_hashInlineCryptFunction(string $bytes)
Generates a digest from $bytes
int
safe_intval(string $x)
Convert float to int
On 32-bit Linux installs running PHP < 5.3 converting floats to ints doesn't always work
string
safe_intval_inline()
eval()'able string for in-line float to int
do_nothing()
Dummy error handler to suppress mcrypt errors
Crypt_RC4()
PHP4 compatible Default Constructor.
string
_crypt(string $text, int $mode)
Encrypts or decrypts a message.