CBCCommon Class Reference

Concrete base class to assist with implementing CBC for 128-bit block ciphers. More...

#include <CBC.h>

Inheritance diagram for CBCCommon:

Public Member Functions
virtual	~CBCCommon ()
	Destroys this cipher object after clearing sensitive information.
size_t	keySize () const
	Default size of the key for this cipher, in bytes. More...
size_t	ivSize () const
	Size of the initialization vector for this cipher, in bytes. More...
bool	setKey (const uint8_t *key, size_t len)
	Sets the key to use for future encryption and decryption operations. More...
bool	setIV (const uint8_t *iv, size_t len)
	Sets the initialization vector to use for future encryption and decryption operations. More...
void	encrypt (uint8_t *output, const uint8_t *input, size_t len)
	Encrypts an input buffer and writes the ciphertext to an output buffer. More...
void	decrypt (uint8_t *output, const uint8_t *input, size_t len)
	Decrypts an input buffer and writes the plaintext to an output buffer. More...
void	clear ()
	Clears all security-sensitive state from this cipher. More...
Public Member Functions inherited from Cipher
	Cipher ()
	Constructs a new cipher object.
virtual	~Cipher ()
	Destroys this cipher object. More...

Protected Member Functions
	CBCCommon ()
	Constructs a new cipher in CBC mode. More...
void	setBlockCipher (BlockCipher *cipher)
	Sets the block cipher to use for this CBC object. More...

Detailed Description

Concrete base class to assist with implementing CBC for 128-bit block ciphers.

Reference: http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation

See also

CBC

Definition at line 29 of file CBC.h.

Constructor & Destructor Documentation

CBCCommon()

CBCCommon::CBCCommon ( )

protected

Constructs a new cipher in CBC mode.

This constructor should be followed by a call to setBlockCipher().

Definition at line 42 of file CBC.cpp.

Member Function Documentation

clear()

void CBCCommon::clear ( )

virtual

Clears all security-sensitive state from this cipher.

Security-sensitive information includes key schedules, initialization vectors, and any temporary state that is used by encrypt() or decrypt() which is stored in the cipher itself.

Implements Cipher.

Definition at line 113 of file CBC.cpp.

decrypt()

void CBCCommon::decrypt ( uint8_t *  output, const uint8_t *  input, size_t  len  )

virtual

Decrypts an input buffer and writes the plaintext to an output buffer.

Parameters

output	The output buffer to write to, which may be the same buffer as input. The output buffer must have at least as many bytes as the input buffer.
input	The input buffer to read from.
len	The number of bytes to decrypt.

The decrypt() function can be called multiple times with different regions of the ciphertext data.

See also

encrypt()

Implements Cipher.

Definition at line 99 of file CBC.cpp.

encrypt()

void CBCCommon::encrypt ( uint8_t *  output, const uint8_t *  input, size_t  len  )

virtual

Encrypts an input buffer and writes the ciphertext to an output buffer.

Parameters

output	The output buffer to write to, which may be the same buffer as input. The output buffer must have at least as many bytes as the input buffer.
input	The input buffer to read from.
len	The number of bytes to encrypt.

The encrypt() function can be called multiple times with different regions of the plaintext data.

See also

decrypt()

Implements Cipher.

Definition at line 86 of file CBC.cpp.

ivSize()

size_t CBCCommon::ivSize ( ) const

virtual

Size of the initialization vector for this cipher, in bytes.

If the cipher does not need an initialization vector, this function will return zero.

Implements Cipher.

Definition at line 62 of file CBC.cpp.

keySize()

size_t CBCCommon::keySize ( ) const

virtual

Default size of the key for this cipher, in bytes.

If the cipher supports variable-sized keys, keySize() indicates the default or recommended key size. The cipher may support other key sizes.

See also

setKey(), ivSize()

Implements Cipher.

Definition at line 57 of file CBC.cpp.

setBlockCipher()

void CBCCommon::setBlockCipher ( BlockCipher *  cipher )

inlineprotected

Sets the block cipher to use for this CBC object.

Parameters

cipher

The block cipher to use to implement CBC mode, which must have a block size of 16 bytes (128 bits).

Definition at line 47 of file CBC.h.

setIV()

bool CBCCommon::setIV ( const uint8_t *  iv, size_t  len  )

virtual

Sets the initialization vector to use for future encryption and decryption operations.

Parameters

iv	The initialization vector to use.
len	The length of the initialization vector in bytes.

Returns

Returns false if the length is not supported.

Initialization vectors should be set before the first call to encrypt() or decrypt() after a setKey() call. If the initialization vector is changed after encryption or decryption begins, then the behaviour is undefined.

Note

The IV is not encoded into the output stream by encrypt(). The caller is responsible for communicating the IV to the other party.

See also

ivSize()

Implements Cipher.

Definition at line 77 of file CBC.cpp.

setKey()

bool CBCCommon::setKey ( const uint8_t *  key, size_t  len  )

virtual

Sets the key to use for future encryption and decryption operations.

Parameters

key	The key to use.
len	The length of the key in bytes.

Returns

Returns false if the key length is not supported, or the key is somehow "weak" and unusable by this cipher.

Use clear() or the destructor to remove the key and any other sensitive data from the object once encryption or decryption is complete.

Calling setKey() resets the cipher. Any temporary data that was being retained for encrypting partial blocks will be abandoned.

See also

keySize(), clear()

Implements Cipher.

Definition at line 67 of file CBC.cpp.

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The documentation for this class was generated from the following files:

• CBC.h
• CBC.cpp