Crypto++  5.6.5
Free C++ class library of cryptographic schemes
Public Member Functions | List of all members
CBC_CTS_Decryption Class Reference

CBC-CTS block cipher mode of operation decryption operation. More...

+ Inheritance diagram for CBC_CTS_Decryption:

Public Member Functions

unsigned int MinLastBlockSize () const
 Provides the size of the last block. More...
 
size_t ProcessLastBlock (byte *outString, size_t outLength, const byte *inString, size_t inLength)
 Encrypt or decrypt the last block of data. More...
 
- Public Member Functions inherited from CBC_Decryption
void ProcessData (byte *outString, const byte *inString, size_t length)
 Encrypt or decrypt an array of bytes. More...
 
- Public Member Functions inherited from CBC_ModeBase
IV_Requirement IVRequirement () const
 Minimal requirement for secure IVs. More...
 
bool RequireAlignedInput () const
 
- Public Member Functions inherited from BlockOrientedCipherModeBase
void UncheckedSetKey (const byte *key, unsigned int length, const NameValuePairs &params)
 Sets the key for this object without performing parameter validation. More...
 
unsigned int MandatoryBlockSize () const
 Provides the mandatory block size of the cipher. More...
 
bool IsRandomAccess () const
 Determines whether the cipher supports random access. More...
 
bool IsSelfInverting () const
 Determines whether the cipher is self-inverting. More...
 
bool IsForwardTransformation () const
 Determines if the cipher is being operated in its forward direction. More...
 
void Resynchronize (const byte *iv, int length=-1)
 Resynchronize with an IV. More...
 
- Public Member Functions inherited from CipherModeBase
size_t MinKeyLength () const
 Returns smallest valid key length. More...
 
size_t MaxKeyLength () const
 Returns largest valid key length. More...
 
size_t DefaultKeyLength () const
 Returns default key length. More...
 
size_t GetValidKeyLength (size_t n) const
 Returns a valid key length for the algorithm. More...
 
bool IsValidKeyLength (size_t n) const
 Returns whether keylength is a valid key length. More...
 
unsigned int OptimalDataAlignment () const
 Provides input and output data alignment for optimal performance. More...
 
unsigned int IVSize () const
 Returns length of the IV accepted by this object. More...
 
void SetCipher (BlockCipher &cipher)
 
void SetCipherWithIV (BlockCipher &cipher, const byte *iv, int feedbackSize=0)
 
- Public Member Functions inherited from SimpleKeyingInterface
virtual void SetKey (const byte *key, size_t length, const NameValuePairs &params=g_nullNameValuePairs)
 Sets or reset the key of this object. More...
 
void SetKeyWithRounds (const byte *key, size_t length, int rounds)
 Sets or reset the key of this object. More...
 
void SetKeyWithIV (const byte *key, size_t length, const byte *iv, size_t ivLength)
 Sets or reset the key of this object. More...
 
void SetKeyWithIV (const byte *key, size_t length, const byte *iv)
 Sets or reset the key of this object. More...
 
bool IsResynchronizable () const
 Determines if the object can be resynchronized. More...
 
bool CanUseRandomIVs () const
 Determines if the object can use random IVs. More...
 
bool CanUsePredictableIVs () const
 Determines if the object can use random but possibly predictable IVs. More...
 
bool CanUseStructuredIVs () const
 Determines if the object can use structured IVs. More...
 
unsigned int DefaultIVLength () const
 Provides the default size of an IV. More...
 
virtual unsigned int MinIVLength () const
 Provides the minimum size of an IV. More...
 
virtual unsigned int MaxIVLength () const
 Provides the maximum size of an IV. More...
 
virtual void GetNextIV (RandomNumberGenerator &rng, byte *iv)
 Retrieves a secure IV for the next message. More...
 
- Public Member Functions inherited from StreamTransformation
StreamTransformationRef ()
 Provides a reference to this object. More...
 
virtual unsigned int OptimalBlockSize () const
 Provides the input block size most efficient for this cipher. More...
 
virtual unsigned int GetOptimalBlockSizeUsed () const
 Provides the number of bytes used in the current block when processing at optimal block size. More...
 
virtual bool IsLastBlockSpecial () const
 Determines if the last block receives special processing. More...
 
void ProcessString (byte *inoutString, size_t length)
 Encrypt or decrypt a string of bytes. More...
 
void ProcessString (byte *outString, const byte *inString, size_t length)
 Encrypt or decrypt a string of bytes. More...
 
byte ProcessByte (byte input)
 Encrypt or decrypt a byte. More...
 
virtual void Seek (lword pos)
 Seek to an absolute position. More...
 
- Public Member Functions inherited from Algorithm
 Algorithm (bool checkSelfTestStatus=true)
 Interface for all crypto algorithms. More...
 
virtual std::string AlgorithmName () const
 Provides the name of this algorithm. More...
 
- Public Member Functions inherited from Clonable
virtual ClonableClone () const
 Copies this object. More...
 

Additional Inherited Members

- Public Types inherited from SimpleKeyingInterface
enum  IV_Requirement {
  UNIQUE_IV = 0, RANDOM_IV, UNPREDICTABLE_RANDOM_IV, INTERNALLY_GENERATED_IV,
  NOT_RESYNCHRONIZABLE
}
 Secure IVs requirements as enumerated values. More...
 
- Static Public Member Functions inherited from CBC_ModeBase
static const char * StaticAlgorithmName ()
 

Detailed Description

CBC-CTS block cipher mode of operation decryption operation.

Definition at line 273 of file modes.h.

Member Function Documentation

◆ MinLastBlockSize()

unsigned int CBC_CTS_Decryption::MinLastBlockSize ( ) const
inlinevirtual

Provides the size of the last block.

Returns
the minimum size of the last block

MinLastBlockSize() returns the minimum size of the last block. 0 indicates the last block is not special.

MandatoryBlockSize() enlists one of two behaviors. First, if MandatoryBlockSize() returns 1, then the cipher can be streamed and ProcessData() is called with the tail bytes. Second, if MandatoryBlockSize() returns non-0, then the string of bytes is padded to MandatoryBlockSize() according to the padding mode. Then, ProcessData() is called with the padded string of bytes.

Some authenticated encryption modes are not expressed well with MandatoryBlockSize() and MinLastBlockSize(). For example, AES/OCB uses 16-byte blocks (MandatoryBlockSize = 16) and the last block requires special processing (MinLastBlockSize = 0). However, 0 is a valid last block size for OCB and the special processing is custom padding, and not standard PKCS padding. In response an unambiguous IsLastBlockSpecial() was added.

See also
ProcessData, ProcessLastBlock, MandatoryBlockSize, MinLastBlockSize, BlockPaddingSchemeDef, IsLastBlockSpecial

Reimplemented from CBC_ModeBase.

Definition at line 276 of file modes.h.

◆ ProcessLastBlock()

size_t CBC_CTS_Decryption::ProcessLastBlock ( byte *  outString,
size_t  outLength,
const byte *  inString,
size_t  inLength 
)
virtual

Encrypt or decrypt the last block of data.

Parameters
outStringthe output byte buffer
outLengththe size of the output byte buffer, in bytes
inStringthe input byte buffer
inLengththe size of the input byte buffer, in bytes
Returns
the number of bytes used in outString

ProcessLastBlock is used when the last block of data is special and requires handling by the cipher. The current implementation provides an output buffer with a size inLength+2*MandatoryBlockSize(). The return value allows the cipher to expand cipher text during encryption or shrink plain text during decryption.

This member function is used by CBC-CTS and OCB modes.

See also
ProcessData, ProcessLastBlock, MandatoryBlockSize, MinLastBlockSize, BlockPaddingSchemeDef, IsLastBlockSpecial

Reimplemented from StreamTransformation.

Definition at line 238 of file modes.cpp.


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