RC4

Default Constructor.

Determines whether or not the mcrypt extension should be used.

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}

Sets the key length

Keys can be between 1 and 256 bytes long.

Returns the current key length in bits

Returns the current block length in bits

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.

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

Encrypts a message.

Decrypts a message.

$this->decrypt($this->encrypt($plaintext)) == $this->encrypt($this->encrypt($plaintext)). At least if the continuous buffer is disabled.

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.

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().

phpseclib <-> OpenSSL Mode Mapper

May need to be overwritten by classes extending this one in some cases

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)

Do not pad packets.

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 \phpseclib\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.

Treat consecutive packets as if they are a discontinuous buffer.

The default behavior.

Test for engine validity

This is mainly just a wrapper to set things up for \phpseclib\Crypt\Base::isValidEngine()

Sets the preferred crypt engine

Currently, $engine could be:

• \phpseclib\Crypt\Base::ENGINE_OPENSSL [very fast]

• \phpseclib\Crypt\Base::ENGINE_MCRYPT [fast]

• \phpseclib\Crypt\Base::ENGINE_INTERNAL [slow]

If the preferred crypt engine is not available the fastest available one will be used

Returns the engine currently being utilized

Sets the engine as appropriate

Encrypts a block

Decrypts a block

Setup the key (expansion)

Setup the self::ENGINE_INTERNAL $engine

(re)init, if necessary, the internal cipher $engine and flush all $buffers Used (only) if $engine == self::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

Setup the self::ENGINE_MCRYPT $engine

(re)init, if necessary, the (ext)mcrypt resources and flush all $buffers Used (only) if $engine = self::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()

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.

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.

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 Shift

Inspired by array_shift

String Pop

Inspired by array_pop

Increment the current string

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 == self::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 \phpseclib\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

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 );

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.

Generates a digest from $bytes

Convert float to int

On ARM CPUs converting floats to ints doesn't always work

eval()'able string for in-line float to int

Dummy error handler to suppress mcrypt errors

Encrypts or decrypts a message.