QCA::Cipher Class Reference
[QCA user API]

General class for cipher (encryption / decryption) algorithms. More...

#include <QtCrypto>

Collaboration diagram for QCA::Cipher:
Collaboration graph
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List of all members.

Public Types

enum  Mode { CBC, CFB, ECB, OFB }
enum  Padding { DefaultPadding, NoPadding, PKCS7 }

Public Member Functions

int blockSize () const
 Cipher (const Cipher &from)
 Cipher (const QString &type, Mode mode, Padding pad=DefaultPadding, Direction dir=Encode, const SymmetricKey &key=SymmetricKey(), const InitializationVector &iv=InitializationVector(), const QString &provider=QString())
virtual void clear ()
Direction direction () const
virtual MemoryRegion final ()
KeyLength keyLength () const
Mode mode () const
virtual bool ok () const
Cipheroperator= (const Cipher &from)
Padding padding () const
void setup (Direction dir, const SymmetricKey &key, const InitializationVector &iv=InitializationVector())
QString type () const
virtual MemoryRegion update (const MemoryRegion &a)
bool validKeyLength (int n) const

Static Public Member Functions

static QStringList supportedTypes (const QString &provider=QString())
static QString withAlgorithms (const QString &cipherType, Mode modeType, Padding paddingType)

Detailed Description

General class for cipher (encryption / decryption) algorithms.

Cipher is the class for the various algorithms that perform low level encryption and decryption within QCA.

AES128, AES192 and AES256 are recommended for new applications.

Standard names for ciphers are:

When checking for the availability of a particular kind of cipher operation (e.g. AES128 in CBC mode with PKCS7 padding), you append the mode and padding type (in that example "aes128-cbc-pkcs7"). CFB and OFB modes don't use padding, so they are always just the cipher name followed by the mode (e.g. "blowfish-cfb" or "aes192-ofb"). If you are not using padding with CBC mode (i.e. you are ensuring block size operations yourself), just use the cipher name followed by "-cbc" (e.g. "blowfish-cbc" or "aes256-cbc").

Examples:

aes-cmac.cpp, and ciphertest.cpp.


Member Enumeration Documentation

Mode settings for cipher algorithms.

Note:
ECB is almost never what you want, unless you are trying to implement a Cipher variation that is not supported by QCA.
Enumerator:
CBC 

operate in Cipher Block Chaining mode

CFB 

operate in Cipher FeedBack mode

ECB 

operate in Electronic Code Book mode

OFB 

operate in Output FeedBack Mode

Padding variations for cipher algorithms.

See the Padding description for more details on padding schemes.

Enumerator:
DefaultPadding 

Default for cipher-mode.

NoPadding 

Do not use padding.

PKCS7 

Pad using the scheme in PKCS#7.


Constructor & Destructor Documentation

QCA::Cipher::Cipher ( const QString type,
Mode  mode,
Padding  pad = DefaultPadding,
Direction  dir = Encode,
const SymmetricKey key = SymmetricKey(),
const InitializationVector iv = InitializationVector(),
const QString provider = QString() 
)

Standard constructor.

Parameters:
type the name of the cipher specialisation to use (e.g. "aes128")
mode the operating Mode to use (e.g. QCA::Cipher::CBC)
pad the type of Padding to use
dir the Direction that this Cipher should use (Encode for encryption, Decode for decryption)
key the SymmetricKey array that is the key
iv the InitializationVector to use (not used for ECB mode)
provider the name of the Provider to use
Note:
Padding only applies to CBC and ECB modes. CFB and OFB ciphertext is always the length of the plaintext.
QCA::Cipher::Cipher ( const Cipher from  ) 

Standard copy constructor.

Parameters:
from the Cipher to copy state from

Member Function Documentation

Cipher& QCA::Cipher::operator= ( const Cipher from  ) 

Assignment operator.

Parameters:
from the Cipher to copy state from
static QStringList QCA::Cipher::supportedTypes ( const QString provider = QString()  )  [static]

Returns a list of all of the cipher types available.

Parameters:
provider the name of the provider to get a list from, if one provider is required. If not specified, available cipher types from all providers will be returned.
QString QCA::Cipher::type (  )  const

Return the cipher type.

Reimplemented from QCA::Algorithm.

Mode QCA::Cipher::mode (  )  const

Return the cipher mode.

Padding QCA::Cipher::padding (  )  const

Return the cipher padding type.

Direction QCA::Cipher::direction (  )  const

Return the cipher direction.

KeyLength QCA::Cipher::keyLength (  )  const

Return acceptable key lengths.

bool QCA::Cipher::validKeyLength ( int  n  )  const

Test if a key length is valid for the cipher algorithm.

Parameters:
n the key length in bytes
Returns:
true if the key would be valid for the current algorithm
int QCA::Cipher::blockSize (  )  const

return the block size for the cipher object

virtual void QCA::Cipher::clear (  )  [virtual]

reset the cipher object, to allow re-use

Implements QCA::Filter.

virtual MemoryRegion QCA::Cipher::update ( const MemoryRegion a  )  [virtual]

pass in a byte array of data, which will be encrypted or decrypted (according to the Direction that was set in the constructor or in setup() ) and returned.

Parameters:
a the array of data to encrypt / decrypt

Implements QCA::Filter.

Examples:
ciphertest.cpp.
virtual MemoryRegion QCA::Cipher::final (  )  [virtual]

complete the block of data, padding as required, and returning the completed block

Implements QCA::Filter.

Examples:
ciphertest.cpp.
virtual bool QCA::Cipher::ok (  )  const [virtual]

Test if an update() or final() call succeeded.

Returns:
true if the previous call succeeded

Implements QCA::Filter.

Examples:
ciphertest.cpp.
void QCA::Cipher::setup ( Direction  dir,
const SymmetricKey key,
const InitializationVector iv = InitializationVector() 
)

Reset / reconfigure the Cipher.

You can use this to re-use an existing Cipher, rather than creating a new object with a slightly different configuration.

Parameters:
dir the Direction that this Cipher should use (Encode for encryption, Decode for decryption)
key the SymmetricKey array that is the key
iv the InitializationVector to use (not used for ECB Mode)
Note:
You should not leave iv empty for any Mode except ECB.
Examples:
ciphertest.cpp.
static QString QCA::Cipher::withAlgorithms ( const QString cipherType,
Mode  modeType,
Padding  paddingType 
) [static]

Construct a Cipher type string.

Parameters:
cipherType the name of the algorithm (eg AES128, DES)
modeType the mode to operate the cipher in (eg QCA::CBC, QCA::CFB)
paddingType the padding required (eg QCA::NoPadding, QCA::PCKS7)

The documentation for this class was generated from the following file:
Generated on Sat Nov 27 13:41:18 2010 for Qt Cryptographic Architecture by  doxygen 1.6.3